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5 <title>The Altus Metrum System</title>
6 <subtitle>An Owner's Manual for TeleMetrum, TeleMini and TeleDongle Devices</subtitle>
9 <firstname>Bdale</firstname>
10 <surname>Garbee</surname>
13 <firstname>Keith</firstname>
14 <surname>Packard</surname>
17 <firstname>Bob</firstname>
18 <surname>Finch</surname>
21 <firstname>Anthony</firstname>
22 <surname>Towns</surname>
26 <holder>Bdale Garbee and Keith Packard</holder>
30 This document is released under the terms of the
31 <ulink url="http://creativecommons.org/licenses/by-sa/3.0/">
32 Creative Commons ShareAlike 3.0
39 <revnumber>1.0</revnumber>
40 <date>24 August 2011</date>
42 Updated for software version 1.0. Note that 1.0 represents a
43 telemetry format change, meaning both ends of a link
44 (TeleMetrum/TeleMini and TeleDongle) must be updated or
45 communications will fail.
49 <revnumber>0.9</revnumber>
50 <date>18 January 2011</date>
52 Updated for software version 0.9. Note that 0.9 represents a
53 telemetry format change, meaning both ends of a link (TeleMetrum and
54 TeleDongle) must be updated or communications will fail.
58 <revnumber>0.8</revnumber>
59 <date>24 November 2010</date>
60 <revremark>Updated for software version 0.8 </revremark>
66 Thanks to Bob Finch, W9YA, NAR 12965, TRA 12350 for writing "The
67 Mere-Mortals Quick Start/Usage Guide to the Altus Metrum Starter
68 Kit" which formed the basis of the original Getting Started chapter
69 in this manual. Bob was one of our first customers for a production
70 TeleMetrum, and his continued enthusiasm and contributions
71 are immensely gratifying and highly appreciated!
74 And thanks to Anthony (AJ) Towns for major contributions including
75 the AltosUI graphing and site map code and associated documentation.
76 Free software means that our customers and friends can become our
77 collaborators, and we certainly appreciate this level of
81 Have fun using these products, and we hope to meet all of you
82 out on the rocket flight line somewhere.
85 NAR #87103, TRA #12201
88 NAR #88757, TRA #12200
93 <title>Introduction and Overview</title>
95 Welcome to the Altus Metrum community! Our circuits and software reflect
96 our passion for both hobby rocketry and Free Software. We hope their
97 capabilities and performance will delight you in every way, but by
98 releasing all of our hardware and software designs under open licenses,
99 we also hope to empower you to take as active a role in our collective
103 The first device created for our community was TeleMetrum, a dual
104 deploy altimeter with fully integrated GPS and radio telemetry
105 as standard features, and a "companion interface" that will
106 support optional capabilities in the future.
109 The newest device is TeleMini, a dual deploy altimeter with
110 radio telemetry and radio direction finding. This device is only
111 13mm by 38mm (½ inch by 1½ inches) and can fit easily in an 18mm
115 Complementing TeleMetrum and TeleMini is TeleDongle, a USB to RF
116 interface for communicating with the altimeters. Combined with your
117 choice of antenna and
118 notebook computer, TeleDongle and our associated user interface software
119 form a complete ground station capable of logging and displaying in-flight
120 telemetry, aiding rocket recovery, then processing and archiving flight
121 data for analysis and review.
124 More products will be added to the Altus Metrum family over time, and
125 we currently envision that this will be a single, comprehensive manual
126 for the entire product family.
130 <title>Getting Started</title>
132 The first thing to do after you check the inventory of parts in your
133 "starter kit" is to charge the battery.
136 The TeleMetrum battery can be charged by plugging it into the
137 corresponding socket of the TeleMetrum and then using the USB A to
139 cable to plug the TeleMetrum into your computer's USB socket. The
140 TeleMetrum circuitry will charge the battery whenever it is plugged
141 in, because the TeleMetrum's on-off switch does NOT control the
145 When the GPS chip is initially searching for
146 satellites, TeleMetrum will consume more current than it can pull
147 from the USB port, so the battery must be attached in order to get
148 satellite lock. Once GPS is locked, the current consumption goes back
149 down enough to enable charging while
150 running. So it's a good idea to fully charge the battery as your
151 first item of business so there is no issue getting and maintaining
152 satellite lock. The yellow charge indicator led will go out when the
153 battery is nearly full and the charger goes to trickle charge. It
154 can take several hours to fully recharge a deeply discharged battery.
157 The TeleMini battery can be charged by disconnecting it from the
158 TeleMini board and plugging it into a standalone battery charger
159 board, and connecting that via a USB cable to a laptop or other USB
163 The other active device in the starter kit is the TeleDongle USB to
164 RF interface. If you plug it in to your Mac or Linux computer it should
165 "just work", showing up as a serial port device. Windows systems need
166 driver information that is part of the AltOS download to know that the
167 existing USB modem driver will work. We therefore recommend installing
168 our software before plugging in TeleDongle if you are using a Windows
169 computer. If you are using Linux and are having problems, try moving
170 to a fresher kernel (2.6.33 or newer), as the USB serial driver had
171 ugly bugs in some earlier versions.
174 Next you should obtain and install the AltOS software. These include
175 the AltosUI ground station program, current firmware images for
176 TeleMetrum, TeleMini and TeleDongle, and a number of standalone
177 utilities that are rarely needed. Pre-built binary packages are
178 available for Linux, Microsoft Windows, and recent MacOSX versions.
179 Full source code and build instructions are also available.
180 The latest version may always be downloaded from
181 <ulink url="http://altusmetrum.org/AltOS"/>.
185 <title>Handling Precautions</title>
187 All Altus Metrum products are sophisticated electronic devices.
188 When handled gently and properly installed in an air-frame, they
189 will deliver impressive results. However, as with all electronic
190 devices, there are some precautions you must take.
193 The Lithium Polymer rechargeable batteries have an
194 extraordinary power density. This is great because we can fly with
195 much less battery mass than if we used alkaline batteries or previous
196 generation rechargeable batteries... but if they are punctured
197 or their leads are allowed to short, they can and will release their
199 Thus we recommend that you take some care when handling our batteries
200 and consider giving them some extra protection in your air-frame. We
201 often wrap them in suitable scraps of closed-cell packing foam before
202 strapping them down, for example.
205 The barometric sensors used on both TeleMetrum and TeleMini are
206 sensitive to sunlight. In normal TeleMetrum mounting situations, it
207 and all of the other surface mount components
208 are "down" towards whatever the underlying mounting surface is, so
209 this is not normally a problem. Please consider this, though, when
210 designing an installation, for example, in an air-frame with a
211 see-through plastic payload bay. It is particularly important to
212 consider this with TeleMini, both because the baro sensor is on the
213 "top" of the board, and because many model rockets with payload bays
214 use clear plastic for the payload bay! Replacing these with an opaque
215 cardboard tube, painting them, or wrapping them with a layer of masking
216 tape are all reasonable approaches to keep the sensor out of direct
220 The barometric sensor sampling port must be able to "breathe",
221 both by not being covered by foam or tape or other materials that might
222 directly block the hole on the top of the sensor, and also by having a
223 suitable static vent to outside air.
226 As with all other rocketry electronics, Altus Metrum altimeters must
227 be protected from exposure to corrosive motor exhaust and ejection
232 <title>Hardware Overview</title>
234 TeleMetrum is a 1 inch by 2.75 inch circuit board. It was designed to
235 fit inside coupler for 29mm air-frame tubing, but using it in a tube that
236 small in diameter may require some creativity in mounting and wiring
237 to succeed! The presence of an accelerometer means TeleMetrum should
238 be aligned along the flight axis of the airframe, and by default the 1/4
239 wave UHF wire antenna should be on the nose-cone end of the board. The
240 antenna wire is about 7 inches long, and wiring for a power switch and
241 the e-matches for apogee and main ejection charges depart from the
242 fin can end of the board, meaning an ideal "simple" avionics
243 bay for TeleMetrum should have at least 10 inches of interior length.
246 TeleMini is a 0.5 inch by 1.5 inch circuit board. It was designed to
247 fit inside an 18mm air-frame tube, but using it in a tube that
248 small in diameter may require some creativity in mounting and wiring
249 to succeed! Since there is no accelerometer, TeleMini can be mounted
250 in any convenient orientation. The default 1/4
251 wave UHF wire antenna attached to the center of one end of
252 the board is about 7 inches long, and wiring for a power switch and
253 the e-matches for apogee and main ejection charges depart from the
254 other end of the board, meaning an ideal "simple" avionics
255 bay for TeleMini should have at least 9 inches of interior length.
258 A typical TeleMetrum or TeleMini installation involves attaching
259 only a suitable Lithium Polymer battery, a single pole switch for
260 power on/off, and two pairs of wires connecting e-matches for the
261 apogee and main ejection charges. All Altus Metrum products are
262 designed for use with single-cell batteries with 3.7 volts nominal.
265 By default, we use the unregulated output of the Li-Po battery directly
266 to fire ejection charges. This works marvelously with standard
267 low-current e-matches like the J-Tek from MJG Technologies, and with
268 Quest Q2G2 igniters. However, if you want or need to use a separate
269 pyro battery, check out the "External Pyro Battery" section in this
270 manual for instructions on how to wire that up. The altimeters are
271 designed to work with an external pyro battery of no more than 15 volts.
274 Ejection charges are wired directly to the screw terminal block
275 at the aft end of the altimeter. You'll need a very small straight
276 blade screwdriver for these screws, such as you might find in a
277 jeweler's screwdriver set.
280 TeleMetrum also uses the screw terminal block for the power
281 switch leads. On TeleMini, the power switch leads are soldered
282 directly to the board and can be connected directly to a switch.
285 For most air-frames, the integrated antennas are more than
286 adequate. However, if you are installing in a carbon-fiber or
287 metal electronics bay which is opaque to RF signals, you may need to
288 use off-board external antennas instead. In this case, you can
289 order an altimeter with an SMA connector for the UHF antenna
290 connection, and, on TeleMetrum, you can unplug the integrated GPS
291 antenna and select an appropriate off-board GPS antenna with
292 cable terminating in a U.FL connector.
296 <title>System Operation</title>
298 <title>Firmware Modes </title>
300 The AltOS firmware build for the altimeters has two
301 fundamental modes, "idle" and "flight". Which of these modes
302 the firmware operates in is determined at start up time. For
303 TeleMetrum, the mode is controlled by the orientation of the
304 rocket (well, actually the board, of course...) at the time
305 power is switched on. If the rocket is "nose up", then
306 TeleMetrum assumes it's on a rail or rod being prepared for
307 launch, so the firmware chooses flight mode. However, if the
308 rocket is more or less horizontal, the firmware instead enters
309 idle mode. Since TeleMini doesn't have an accelerometer we can
310 use to determine orientation, "idle" mode is selected when the
311 board receives a command packet within the first five seconds
312 of operation; if no packet is received, the board enters
316 At power on, you will hear three beeps or see three flashes
317 ("S" in Morse code for start up) and then a pause while
318 the altimeter completes initialization and self test, and decides
319 which mode to enter next.
322 In flight or "pad" mode, the altimeter engages the flight
323 state machine, goes into transmit-only mode to
324 send telemetry, and waits for launch to be detected.
325 Flight mode is indicated by an "di-dah-dah-dit" ("P" for pad)
326 on the beeper or lights, followed by beeps or flashes
327 indicating the state of the pyrotechnic igniter continuity.
328 One beep/flash indicates apogee continuity, two beeps/flashes
329 indicate main continuity, three beeps/flashes indicate both
330 apogee and main continuity, and one longer "brap" sound or
331 rapidly alternating lights indicates no continuity. For a
332 dual deploy flight, make sure you're getting three beeps or
333 flashes before launching! For apogee-only or motor eject
334 flights, do what makes sense.
337 If idle mode is entered, you will hear an audible "di-dit" or see
338 two short flashes ("I" for idle), and the flight state machine is
339 disengaged, thus no ejection charges will fire. The altimeters also
340 listen for the radio link when in idle mode for requests sent via
341 TeleDongle. Commands can be issued to a TeleMetrum in idle mode
343 USB or the radio link equivalently. TeleMini only has the radio link.
344 Idle mode is useful for configuring the altimeter, for extracting data
345 from the on-board storage chip after flight, and for ground testing
349 One "neat trick" of particular value when TeleMetrum is used with
350 very large air-frames, is that you can power the board up while the
351 rocket is horizontal, such that it comes up in idle mode. Then you can
352 raise the air-frame to launch position, and issue a 'reset' command
353 via TeleDongle over the radio link to cause the altimeter to reboot and
354 come up in flight mode. This is much safer than standing on the top
355 step of a rickety step-ladder or hanging off the side of a launch
356 tower with a screw-driver trying to turn on your avionics before
363 TeleMetrum includes a complete GPS receiver. A complete explanation
364 of how GPS works is beyond the scope of this manual, but the bottom
365 line is that the TeleMetrum GPS receiver needs to lock onto at least
366 four satellites to obtain a solid 3 dimensional position fix and know
370 TeleMetrum provides backup power to the GPS chip any time a
371 battery is connected. This allows the receiver to "warm start" on
372 the launch rail much faster than if every power-on were a GPS
373 "cold start". In typical operations, powering up TeleMetrum
374 on the flight line in idle mode while performing final air-frame
375 preparation will be sufficient to allow the GPS receiver to cold
376 start and acquire lock. Then the board can be powered down during
377 RSO review and installation on a launch rod or rail. When the board
378 is turned back on, the GPS system should lock very quickly, typically
379 long before igniter installation and return to the flight line are
384 <title>Controlling An Altimeter Over The Radio Link</title>
386 One of the unique features of the Altus Metrum system is
387 the ability to create a two way command link between TeleDongle
388 and an altimeter using the digital radio transceivers built into
389 each device. This allows you to interact with the altimeter from
390 afar, as if it were directly connected to the computer.
393 Any operation which can be performed with TeleMetrum can
394 either be done with TeleMetrum directly connected to the
395 computer via the USB cable, or through the radio
396 link. TeleMini doesn't provide a USB connector and so it is
397 always communicated with over radio. Select the appropriate
398 TeleDongle device when the list of devices is presented and
399 AltosUI will interact with an altimeter over the radio link.
402 One oddity in the current interface is how AltosUI selects the
403 frequency for radio communications. Instead of providing
404 an interface to specifically configure the frequency, it uses
405 whatever frequency was most recently selected for the target
406 TeleDongle device in Monitor Flight mode. If you haven't ever
407 used that mode with the TeleDongle in question, select the
408 Monitor Flight button from the top level UI, and pick the
409 appropriate TeleDongle device. Once the flight monitoring
410 window is open, select the desired frequency and then close it
411 down again. All radio communications will now use that frequency.
416 Save Flight Data—Recover flight data from the rocket without
422 Configure altimeter apogee delays or main deploy heights
423 to respond to changing launch conditions. You can also
424 'reboot' the altimeter. Use this to remotely enable the
425 flight computer by turning TeleMetrum on in "idle" mode,
426 then once the air-frame is oriented for launch, you can
427 reboot the altimeter and have it restart in pad mode
428 without having to climb the scary ladder.
433 Fire Igniters—Test your deployment charges without snaking
434 wires out through holes in the air-frame. Simply assembly the
435 rocket as if for flight with the apogee and main charges
436 loaded, then remotely command the altimeter to fire the
442 Operation over the radio link for configuring an altimeter, ground
443 testing igniters, and so forth uses the same RF frequencies as flight
444 telemetry. To configure the desired TeleDongle frequency, select
445 the monitor flight tab, then use the frequency selector and
446 close the window before performing other desired radio operations.
449 TeleMetrum only enables radio commanding in 'idle' mode, so
450 make sure you have TeleMetrum lying horizontally when you turn
451 it on. Otherwise, TeleMetrum will start in 'pad' mode ready for
452 flight, and will not be listening for command packets from TeleDongle.
455 TeleMini listens for a command packet for five seconds after
456 first being turned on, if it doesn't hear anything, it enters
457 'pad' mode, ready for flight and will no longer listen for
458 command packets. The easiest way to connect to TeleMini is to
459 initiate the command and select the TeleDongle device. At this
460 point, the TeleDongle will be attempting to communicate with
461 the TeleMini. Now turn TeleMini on, and it should immediately
462 start communicating with the TeleDongle and the desired
463 operation can be performed.
466 You can monitor the operation of the radio link by watching the
467 lights on the devices. The red LED will flash each time a packet
468 is tramsitted, while the green LED will light up on TeleDongle when
469 it is waiting to receive a packet from the altimeter.
473 <title>Ground Testing </title>
475 An important aspect of preparing a rocket using electronic deployment
476 for flight is ground testing the recovery system. Thanks
477 to the bi-directional radio link central to the Altus Metrum system,
478 this can be accomplished in a TeleMetrum or TeleMini equipped rocket
479 with less work than you may be accustomed to with other systems. It
483 Just prep the rocket for flight, then power up the altimeter
484 in "idle" mode (placing air-frame horizontal for TeleMetrum or
485 selected the Configure Altimeter tab for TeleMini). This will cause
486 the firmware to go into "idle" mode, in which the normal flight
487 state machine is disabled and charges will not fire without
488 manual command. You can now command the altimeter to fire the apogee
489 or main charges from a safe distance using your computer and
490 TeleDongle and the Fire Igniter tab to complete ejection testing.
494 <title>Radio Link </title>
496 The chip our boards are based on incorporates an RF transceiver, but
497 it's not a full duplex system... each end can only be transmitting or
498 receiving at any given moment. So we had to decide how to manage the
502 By design, the altimeter firmware listens for the radio link when
503 it's in "idle mode", which
504 allows us to use the radio link to configure the rocket, do things like
505 ejection tests, and extract data after a flight without having to
506 crack open the air-frame. However, when the board is in "flight
507 mode", the altimeter only
508 transmits and doesn't listen at all. That's because we want to put
509 ultimate priority on event detection and getting telemetry out of
511 the radio in case the rocket crashes and we aren't able to extract
515 We don't use a 'normal packet radio' mode like APRS because they're
516 just too inefficient. The GFSK modulation we use is FSK with the
517 base-band pulses passed through a
518 Gaussian filter before they go into the modulator to limit the
519 transmitted bandwidth. When combined with the hardware forward error
520 correction support in the cc1111 chip, this allows us to have a very
521 robust 38.4 kilobit data link with only 10 milliwatts of transmit
522 power, a whip antenna in the rocket, and a hand-held Yagi on the
523 ground. We've had flights to above 21k feet AGL with great reception,
524 and calculations suggest we should be good to well over 40k feet AGL
525 with a 5-element yagi on the ground. We hope to fly boards to higher
526 altitudes over time, and would of course appreciate customer feedback
527 on performance in higher altitude flights!
531 <title>Configurable Parameters</title>
533 Configuring an Altus Metrum altimeter for flight is very
534 simple. Even on our baro-only TeleMini board, the use of a Kalman
535 filter means there is no need to set a "mach delay". The few
536 configurable parameters can all be set using AltosUI over USB or
537 or radio link via TeleDongle.
540 <title>Radio Frequency</title>
542 Altus Metrum boards support radio frequencies in the 70cm
543 band. By default, the configuration interface provides a
544 list of 10 "standard" frequencies in 100kHz channels starting at
545 434.550MHz. However, the firmware supports use of
546 any 50kHz multiple within the 70cm band. At any given
547 launch, we highly recommend coordinating when and by whom each
548 frequency will be used to avoid interference. And of course, both
549 altimeter and TeleDongle must be configured to the same
550 frequency to successfully communicate with each other.
554 <title>Apogee Delay</title>
556 Apogee delay is the number of seconds after the altimeter detects flight
557 apogee that the drogue charge should be fired. In most cases, this
558 should be left at the default of 0. However, if you are flying
559 redundant electronics such as for an L3 certification, you may wish
560 to set one of your altimeters to a positive delay so that both
561 primary and backup pyrotechnic charges do not fire simultaneously.
564 The Altus Metrum apogee detection algorithm fires exactly at
565 apogee. If you are also flying an altimeter like the
566 PerfectFlite MAWD, which only supports selecting 0 or 1
567 seconds of apogee delay, you may wish to set the MAWD to 0
568 seconds delay and set the TeleMetrum to fire your backup 2
569 or 3 seconds later to avoid any chance of both charges
570 firing simultaneously. We've flown several air-frames this
571 way quite happily, including Keith's successful L3 cert.
575 <title>Main Deployment Altitude</title>
577 By default, the altimeter will fire the main deployment charge at an
578 elevation of 250 meters (about 820 feet) above ground. We think this
579 is a good elevation for most air-frames, but feel free to change this
580 to suit. In particular, if you are flying two altimeters, you may
582 deployment elevation for the backup altimeter to be something lower
583 than the primary so that both pyrotechnic charges don't fire
588 <title>Maximum Flight Log</title>
590 TeleMetrum version 1.1 and 1.2 have 2MB of on-board flash storage,
591 enough to hold over 40 minutes of data at full data rate
592 (100 samples/second). TeleMetrum 1.0 has 1MB of on-board
593 storage. As data are stored at a reduced rate during descent
594 (10 samples/second), there's plenty of space to store many
595 flights worth of data.
598 The on-board flash is partitioned into separate flight logs,
599 each of a fixed maximum size. Increase the maximum size of
600 each log and you reduce the number of flights that can be
601 stored. Decrease the size and TeleMetrum can store more
605 All of the configuration data is also stored in the flash
606 memory, which consumes 64kB on TeleMetrum v1.1/v1.2 and 256B on
607 TeleMetrum v1.0. This configuration space is not available
608 for storing flight log data.
611 To compute the amount of space needed for a single flight,
612 you can multiply the expected ascent time (in seconds) by
613 800, multiply the expected descent time (in seconds) by 80
614 and add the two together. That will slightly under-estimate
615 the storage (in bytes) needed for the flight. For instance,
616 a flight spending 20 seconds in ascent and 150 seconds in
617 descent will take about (20 * 800) + (150 * 80) = 28000
618 bytes of storage. You could store dozens of these flights in
622 The default size, 192kB, allows for 10 flights of storage on
623 TeleMetrum v1.1/v1.2 and 5 flights on TeleMetrum v1.0. This
624 ensures that you won't need to erase the memory before
625 flying each time while still allowing more than sufficient
626 storage for each flight.
629 As TeleMini does not contain an accelerometer, it stores
630 data at 10 samples per second during ascent and one sample
631 per second during descent. Each sample is a two byte reading
632 from the barometer. These are stored in 5kB of
633 on-chip flash memory which can hold 256 seconds at the
634 ascent rate or 2560 seconds at the descent rate. Because of
635 the limited storage, TeleMini cannot hold data for more than
636 one flight, and so must be erased after each flight or it
637 will not capture data for subsequent flights.
641 <title>Ignite Mode</title>
643 Instead of firing one charge at apogee and another charge at
644 a fixed height above the ground, you can configure the
645 altimeter to fire both at apogee or both during
646 descent. This was added to support an airframe that has two
647 TeleMetrum computers, one in the fin can and one in the
651 Providing the ability to use both igniters for apogee or
652 main allows some level of redundancy without needing two
653 flight computers. In Redundant Apogee or Redundant Main
654 mode, the two charges will be fired two seconds apart.
658 <title>Pad Orientation</title>
660 TeleMetrum measures acceleration along the axis of the
661 board. Which way the board is oriented affects the sign of
662 the acceleration value. Instead of trying to guess which way
663 the board is mounted in the air frame, TeleMetrum must be
664 explicitly configured for either Antenna Up or Antenna
665 Down. The default, Antenna Up, expects the end of the
666 TeleMetrum board connected to the 70cm antenna to be nearest
667 the nose of the rocket, with the end containing the screw
668 terminals nearest the tail.
676 <title>AltosUI</title>
678 The AltosUI program provides a graphical user interface for
679 interacting with the Altus Metrum product family, including
680 TeleMetrum, TeleMini and TeleDongle. AltosUI can monitor telemetry data,
681 configure TeleMetrum, TeleMini and TeleDongle devices and many other
682 tasks. The primary interface window provides a selection of
683 buttons, one for each major activity in the system. This manual
684 is split into chapters, each of which documents one of the tasks
685 provided from the top-level toolbar.
688 <title>Monitor Flight</title>
689 <subtitle>Receive, Record and Display Telemetry Data</subtitle>
691 Selecting this item brings up a dialog box listing all of the
692 connected TeleDongle devices. When you choose one of these,
693 AltosUI will create a window to display telemetry data as
694 received by the selected TeleDongle device.
697 All telemetry data received are automatically recorded in
698 suitable log files. The name of the files includes the current
699 date and rocket serial and flight numbers.
702 The radio frequency being monitored by the TeleDongle device is
703 displayed at the top of the window. You can configure the
704 frequency by clicking on the frequency box and selecting the desired
705 frequency. AltosUI remembers the last frequency selected for each
706 TeleDongle and selects that automatically the next time you use
710 Below the TeleDongle frequency selector, the window contains a few
711 significant pieces of information about the altimeter providing
712 the telemetry data stream:
716 <para>The configured call-sign</para>
719 <para>The device serial number</para>
722 <para>The flight number. Each altimeter remembers how many
728 The rocket flight state. Each flight passes through several
729 states including Pad, Boost, Fast, Coast, Drogue, Main and
735 The Received Signal Strength Indicator value. This lets
736 you know how strong a signal TeleDongle is receiving. The
737 radio inside TeleDongle operates down to about -99dBm;
738 weaker signals may not be receivable. The packet link uses
739 error detection and correction techniques which prevent
740 incorrect data from being reported.
745 Finally, the largest portion of the window contains a set of
746 tabs, each of which contain some information about the rocket.
747 They're arranged in 'flight order' so that as the flight
748 progresses, the selected tab automatically switches to display
749 data relevant to the current state of the flight. You can select
750 other tabs at any time. The final 'table' tab displays all of
751 the raw telemetry values in one place in a spreadsheet-like format.
754 <title>Launch Pad</title>
756 The 'Launch Pad' tab shows information used to decide when the
757 rocket is ready for flight. The first elements include red/green
758 indicators, if any of these is red, you'll want to evaluate
759 whether the rocket is ready to launch:
763 Battery Voltage. This indicates whether the Li-Po battery
764 powering the TeleMetrum has sufficient charge to last for
765 the duration of the flight. A value of more than
766 3.7V is required for a 'GO' status.
771 Apogee Igniter Voltage. This indicates whether the apogee
772 igniter has continuity. If the igniter has a low
773 resistance, then the voltage measured here will be close
774 to the Li-Po battery voltage. A value greater than 3.2V is
775 required for a 'GO' status.
780 Main Igniter Voltage. This indicates whether the main
781 igniter has continuity. If the igniter has a low
782 resistance, then the voltage measured here will be close
783 to the Li-Po battery voltage. A value greater than 3.2V is
784 required for a 'GO' status.
789 On-board Data Logging. This indicates whether there is
790 space remaining on-board to store flight data for the
791 upcoming flight. If you've downloaded data, but failed
792 to erase flights, there may not be any space
793 left. TeleMetrum can store multiple flights, depending
794 on the configured maximum flight log size. TeleMini
795 stores only a single flight, so it will need to be
796 downloaded and erased after each flight to capture
797 data. This only affects on-board flight logging; the
798 altimeter will still transmit telemetry and fire
799 ejection charges at the proper times.
804 GPS Locked. For a TeleMetrum device, this indicates whether the GPS receiver is
805 currently able to compute position information. GPS requires
806 at least 4 satellites to compute an accurate position.
811 GPS Ready. For a TeleMetrum device, this indicates whether GPS has reported at least
812 10 consecutive positions without losing lock. This ensures
813 that the GPS receiver has reliable reception from the
819 The Launchpad tab also shows the computed launch pad position
820 and altitude, averaging many reported positions to improve the
826 <title>Ascent</title>
828 This tab is shown during Boost, Fast and Coast
829 phases. The information displayed here helps monitor the
830 rocket as it heads towards apogee.
833 The height, speed and acceleration are shown along with the
834 maximum values for each of them. This allows you to quickly
835 answer the most commonly asked questions you'll hear during
839 The current latitude and longitude reported by the TeleMetrum GPS are
840 also shown. Note that under high acceleration, these values
841 may not get updated as the GPS receiver loses position
842 fix. Once the rocket starts coasting, the receiver should
843 start reporting position again.
846 Finally, the current igniter voltages are reported as in the
847 Launch Pad tab. This can help diagnose deployment failures
848 caused by wiring which comes loose under high acceleration.
852 <title>Descent</title>
854 Once the rocket has reached apogee and (we hope) activated the
855 apogee charge, attention switches to tracking the rocket on
856 the way back to the ground, and for dual-deploy flights,
857 waiting for the main charge to fire.
860 To monitor whether the apogee charge operated correctly, the
861 current descent rate is reported along with the current
862 height. Good descent rates vary based on the choice of recovery
863 components, but generally range from 15-30m/s on drogue and should
864 be below 10m/s when under the main parachute in a dual-deploy flight.
867 For TeleMetrum altimeters, you can locate the rocket in the sky
868 using the elevation and
869 bearing information to figure out where to look. Elevation is
870 in degrees above the horizon. Bearing is reported in degrees
871 relative to true north. Range can help figure out how big the
872 rocket will appear. Note that all of these values are relative
873 to the pad location. If the elevation is near 90°, the rocket
874 is over the pad, not over you.
877 Finally, the igniter voltages are reported in this tab as
878 well, both to monitor the main charge as well as to see what
879 the status of the apogee charge is. Note that some commercial
880 e-matches are designed to retain continuity even after being
881 fired, and will continue to show as green or return from red to
886 <title>Landed</title>
888 Once the rocket is on the ground, attention switches to
889 recovery. While the radio signal is often lost once the
890 rocket is on the ground, the last reported GPS position is
891 generally within a short distance of the actual landing location.
894 The last reported GPS position is reported both by
895 latitude and longitude as well as a bearing and distance from
896 the launch pad. The distance should give you a good idea of
897 whether to walk or hitch a ride. Take the reported
898 latitude and longitude and enter them into your hand-held GPS
899 unit and have that compute a track to the landing location.
902 Both TeleMini and TeleMetrum will continue to transmit RDF
903 tones after landing, allowing you to locate the rocket by
904 following the radio signal if necessary. You may need to get
905 away from the clutter of the flight line, or even get up on
906 a hill (or your neighbor's RV roof) to receive the RDF signal.
909 The maximum height, speed and acceleration reported
910 during the flight are displayed for your admiring observers.
911 The accuracy of these immediate values depends on the quality
912 of your radio link and how many packets were received.
913 Recovering the on-board data after flight will likely yield
914 more precise results.
917 To get more detailed information about the flight, you can
918 click on the 'Graph Flight' button which will bring up a
919 graph window for the current flight.
923 <title>Site Map</title>
925 When the TeleMetrum has a GPS fix, the Site Map tab will map
926 the rocket's position to make it easier for you to locate the
927 rocket, both while it is in the air, and when it has landed. The
928 rocket's state is indicated by color: white for pad, red for
929 boost, pink for fast, yellow for coast, light blue for drogue,
930 dark blue for main, and black for landed.
933 The map's scale is approximately 3m (10ft) per pixel. The map
934 can be dragged using the left mouse button. The map will attempt
935 to keep the rocket roughly centered while data is being received.
938 Images are fetched automatically via the Google Maps Static API,
939 and cached on disk for reuse. If map images cannot be downloaded,
940 the rocket's path will be traced on a dark gray background
944 You can pre-load images for your favorite launch sites
945 before you leave home; check out the 'Preload Maps' section below.
950 <title>Save Flight Data</title>
952 The altimeter records flight data to its internal flash memory.
953 TeleMetrum data is recorded at a much higher rate than the telemetry
954 system can handle, and is not subject to radio drop-outs. As
955 such, it provides a more complete and precise record of the
956 flight. The 'Save Flight Data' button allows you to read the
957 flash memory and write it to disk. As TeleMini has only a barometer, it
958 records data at the same rate as the telemetry signal, but there will be
959 no data lost due to telemetry drop-outs.
962 Clicking on the 'Save Flight Data' button brings up a list of
963 connected TeleMetrum and TeleDongle devices. If you select a
964 TeleMetrum device, the flight data will be downloaded from that
965 device directly. If you select a TeleDongle device, flight data
966 will be downloaded from an altimeter over radio link via the
967 specified TeleDongle. See the chapter on Controlling An Altimeter
968 Over The Radio Link for more information.
971 After the device has been selected, a dialog showing the
972 flight data saved in the device will be shown allowing you to
973 select which flights to download and which to delete. With
974 version 0.9 or newer firmware, you must erase flights in order
975 for the space they consume to be reused by another
976 flight. This prevents accidentally losing flight data
977 if you neglect to download data before flying again. Note that
978 if there is no more space available in the device, then no
979 data will be recorded during the next flight.
982 The file name for each flight log is computed automatically
983 from the recorded flight date, altimeter serial number and
984 flight number information.
988 <title>Replay Flight</title>
990 Select this button and you are prompted to select a flight
991 record file, either a .telem file recording telemetry data or a
992 .eeprom file containing flight data saved from the altimeter
996 Once a flight record is selected, the flight monitor interface
997 is displayed and the flight is re-enacted in real time. Check
998 the Monitor Flight chapter above to learn how this window operates.
1002 <title>Graph Data</title>
1004 Select this button and you are prompted to select a flight
1005 record file, either a .telem file recording telemetry data or a
1006 .eeprom file containing flight data saved from
1010 Once a flight record is selected, a window with two tabs is
1011 opened. The first tab contains a graph with acceleration
1012 (blue), velocity (green) and altitude (red) of the flight,
1013 measured in metric units. The
1014 apogee(yellow) and main(magenta) igniter voltages are also
1015 displayed; high voltages indicate continuity, low voltages
1016 indicate open circuits. The second tab contains some basic
1020 The graph can be zoomed into a particular area by clicking and
1021 dragging down and to the right. Once zoomed, the graph can be
1022 reset by clicking and dragging up and to the left. Holding down
1023 control and clicking and dragging allows the graph to be panned.
1024 The right mouse button causes a pop-up menu to be displayed, giving
1025 you the option save or print the plot.
1028 Note that telemetry files will generally produce poor graphs
1029 due to the lower sampling rate and missed telemetry packets.
1030 Use saved flight data in .eeprom files for graphing where possible.
1034 <title>Export Data</title>
1036 This tool takes the raw data files and makes them available for
1037 external analysis. When you select this button, you are prompted to
1039 data file (either .eeprom or .telem will do, remember that
1040 .eeprom files contain higher resolution and more continuous
1041 data). Next, a second dialog appears which is used to select
1042 where to write the resulting file. It has a selector to choose
1043 between CSV and KML file formats.
1046 <title>Comma Separated Value Format</title>
1048 This is a text file containing the data in a form suitable for
1049 import into a spreadsheet or other external data analysis
1050 tool. The first few lines of the file contain the version and
1051 configuration information from the altimeter, then
1052 there is a single header line which labels all of the
1053 fields. All of these lines start with a '#' character which
1054 many tools can be configured to skip over.
1057 The remaining lines of the file contain the data, with each
1058 field separated by a comma and at least one space. All of
1059 the sensor values are converted to standard units, with the
1060 barometric data reported in both pressure, altitude and
1061 height above pad units.
1065 <title>Keyhole Markup Language (for Google Earth)</title>
1067 This is the format used by Google Earth to provide an overlay
1068 within that application. With this, you can use Google Earth to
1069 see the whole flight path in 3D.
1074 <title>Configure Altimeter</title>
1076 Select this button and then select either a TeleMetrum or
1077 TeleDongle Device from the list provided. Selecting a TeleDongle
1078 device will use the radio link to configure a remote altimeter.
1081 The first few lines of the dialog provide information about the
1082 connected device, including the product name,
1083 software version and hardware serial number. Below that are the
1084 individual configuration entries.
1087 At the bottom of the dialog, there are four buttons:
1092 Save. This writes any changes to the
1093 configuration parameter block in flash memory. If you don't
1094 press this button, any changes you make will be lost.
1099 Reset. This resets the dialog to the most recently saved values,
1100 erasing any changes you have made.
1105 Reboot. This reboots the device. Use this to
1106 switch from idle to pad mode by rebooting once the rocket is
1107 oriented for flight, or to confirm changes you think you saved
1113 Close. This closes the dialog. Any unsaved changes will be
1119 The rest of the dialog contains the parameters to be configured.
1122 <title>Main Deploy Altitude</title>
1124 This sets the altitude (above the recorded pad altitude) at
1125 which the 'main' igniter will fire. The drop-down menu shows
1126 some common values, but you can edit the text directly and
1127 choose whatever you like. If the apogee charge fires below
1128 this altitude, then the main charge will fire two seconds
1129 after the apogee charge fires.
1133 <title>Apogee Delay</title>
1135 When flying redundant electronics, it's often important to
1136 ensure that multiple apogee charges don't fire at precisely
1137 the same time, as that can over pressurize the apogee deployment
1138 bay and cause a structural failure of the air-frame. The Apogee
1139 Delay parameter tells the flight computer to fire the apogee
1140 charge a certain number of seconds after apogee has been
1145 <title>Radio Frequency</title>
1147 This configures which of the configured frequencies to use for both
1148 telemetry and packet command mode. Note that if you set this
1149 value via packet command mode, you will have to reconfigure
1150 the TeleDongle frequency before you will be able to use packet
1155 <title>Radio Calibration</title>
1157 The radios in every Altus Metrum device are calibrated at the
1158 factory to ensure that they transmit and receive on the
1159 specified frequency. If you need to you can adjust the calibration
1160 by changing this value. Do not do this without understanding what
1161 the value means, read the appendix on calibration and/or the source
1162 code for more information. To change a TeleDongle's calibration,
1163 you must reprogram the unit completely.
1167 <title>Callsign</title>
1169 This sets the call sign included in each telemetry packet. Set this
1170 as needed to conform to your local radio regulations.
1174 <title>Maximum Flight Log Size</title>
1176 This sets the space (in kilobytes) allocated for each flight
1177 log. The available space will be divided into chunks of this
1178 size. A smaller value will allow more flights to be stored,
1179 a larger value will record data from longer flights.
1183 <title>Ignite Mode</title>
1185 TeleMetrum and TeleMini provide two igniter channels as they
1186 were originally designed as dual-deploy flight
1187 computers. This configuration parameter allows the two
1188 channels to be used in different configurations.
1193 Dual Deploy. This is the usual mode of operation; the
1194 'apogee' channel is fired at apogee and the 'main'
1195 channel at the height above ground specified by the
1196 'Main Deploy Altitude' during descent.
1201 Redundant Apogee. This fires both channels at
1202 apogee, the 'apogee' channel first followed after a two second
1203 delay by the 'main' channel.
1208 Redundant Main. This fires both channels at the
1209 height above ground specified by the Main Deploy
1210 Altitude setting during descent. The 'apogee'
1211 channel is fired first, followed after a two second
1212 delay by the 'main' channel.
1218 <title>Pad Orientation</title>
1220 Because it includes an accelerometer, TeleMetrum is
1221 sensitive to the orientation of the board. By default, it
1222 expects the antenna end to point forward. This parameter
1223 allows that default to be changed, permitting the board to
1224 be mounted with the antenna pointing aft instead.
1229 Antenna Up. In this mode, the antenna end of the
1230 TeleMetrum board must point forward, in line with the
1231 expected flight path.
1236 Antenna Down. In this mode, the antenna end of the
1237 TeleMetrum board must point aft, in line with the
1238 expected flight path.
1245 <title>Configure AltosUI</title>
1247 This button presents a dialog so that you can configure the AltosUI global settings.
1250 <title>Voice Settings</title>
1252 AltosUI provides voice announcements during flight so that you
1253 can keep your eyes on the sky and still get information about
1254 the current flight status. However, sometimes you don't want
1259 <para>Enable—turns all voice announcements on and off</para>
1263 Test Voice—Plays a short message allowing you to verify
1264 that the audio system is working and the volume settings
1271 <title>Log Directory</title>
1273 AltosUI logs all telemetry data and saves all TeleMetrum flash
1274 data to this directory. This directory is also used as the
1275 staring point when selecting data files for display or export.
1278 Click on the directory name to bring up a directory choosing
1279 dialog, select a new directory and click 'Select Directory' to
1280 change where AltosUI reads and writes data files.
1284 <title>Callsign</title>
1286 This value is transmitted in each command packet sent from
1287 TeleDongle and received from an altimeter. It is not used in
1288 telemetry mode, as the callsign configured in the altimeter board
1289 is included in all telemetry packets. Configure this
1290 with the AltosUI operators call sign as needed to comply with
1291 your local radio regulations.
1295 <title>Font Size</title>
1297 Selects the set of fonts used in the flight monitor
1298 window. Choose between the small, medium and large sets.
1302 <title>Serial Debug</title>
1304 This causes all communication with a connected device to be
1305 dumped to the console from which AltosUI was started. If
1306 you've started it from an icon or menu entry, the output
1307 will simply be discarded. This mode can be useful to debug
1308 various serial communication issues.
1312 <title>Manage Frequencies</title>
1314 This brings up a dialog where you can configure the set of
1315 frequencies shown in the various frequency menus. You can
1316 add as many as you like, or even reconfigure the default
1317 set. Changing this list does not affect the frequency
1318 settings of any devices, it only changes the set of
1319 frequencies shown in the menus.
1324 <title>Flash Image</title>
1326 This reprograms any Altus Metrum device by using a TeleMetrum
1327 or TeleDongle as a programming dongle. Please read the
1328 directions for flashing devices in the Updating Device
1329 Firmware chapter below.
1332 Once you have the programmer and target devices connected,
1333 push the 'Flash Image' button. That will present a dialog box
1334 listing all of the connected devices. Carefully select the
1335 programmer device, not the device to be programmed.
1338 Next, select the image to flash to the device. These are named
1339 with the product name and firmware version. The file selector
1340 will start in the directory containing the firmware included
1341 with the AltosUI package. Navigate to the directory containing
1342 the desired firmware if it isn't there.
1345 Next, a small dialog containing the device serial number and
1346 RF calibration values should appear. If these values are
1347 incorrect (possibly due to a corrupted image in the device),
1348 enter the correct values here.
1351 Finally, a dialog containing a progress bar will follow the
1352 programming process.
1355 When programming is complete, the target device will
1356 reboot. Note that if the target device is connected via USB, you
1357 will have to unplug it and then plug it back in for the USB
1358 connection to reset so that you can communicate with the device
1363 <title>Fire Igniter</title>
1365 This activates the igniter circuits in TeleMetrum to help test
1366 recovery systems deployment. Because this command can operate
1367 over the Packet Command Link, you can prepare the rocket as
1368 for flight and then test the recovery system without needing
1369 to snake wires inside the air-frame.
1372 Selecting the 'Fire Igniter' button brings up the usual device
1373 selection dialog. Pick the desired TeleDongle or TeleMetrum
1374 device. This brings up another window which shows the current
1375 continuity test status for both apogee and main charges.
1378 Next, select the desired igniter to fire. This will enable the
1382 Select the 'Arm' button. This enables the 'Fire' button. The
1383 word 'Arm' is replaced by a countdown timer indicating that
1384 you have 10 seconds to press the 'Fire' button or the system
1385 will deactivate, at which point you start over again at
1386 selecting the desired igniter.
1390 <title>Scan Channels</title>
1392 This listens for telemetry packets on all of the configured
1393 frequencies, displaying information about each device it
1394 receives a packet from. You can select which of the three
1395 telemetry formats should be tried; by default, it only listens
1396 for the standard telemetry packets used in v1.0 and later
1401 <title>Load Maps</title>
1403 Before heading out to a new launch site, you can use this to
1404 load satellite images in case you don't have internet
1405 connectivity at the site. This loads a fairly large area
1406 around the launch site, which should cover any flight you're likely to make.
1409 There's a drop-down menu of launch sites we know about; if
1410 your favorites aren't there, please let us know the lat/lon
1411 and name of the site. The contents of this list are actually
1412 downloaded at run-time, so as new sites are sent in, they'll
1413 get automatically added to this list.
1416 If the launch site isn't in the list, you can manually enter the lat/lon values
1419 Clicking the 'Load Map' button will fetch images from Google
1420 Maps; note that Google limits how many images you can fetch at
1421 once, so if you load more than one launch site, you may get
1422 some gray areas in the map which indicate that Google is tired
1423 of sending data to you. Try again later.
1427 <title>Monitor Idle</title>
1429 This brings up a dialog similar to the Monitor Flight UI,
1430 except it works with the altimeter in "idle" mode by sending
1431 query commands to discover the current state rather than
1432 listening for telemetry packets.
1437 <title>Using Altus Metrum Products</title>
1439 <title>Being Legal</title>
1441 First off, in the US, you need an <ulink url="http://www.altusmetrum.org/Radio/">amateur radio license</ulink> or
1442 other authorization to legally operate the radio transmitters that are part
1447 <title>In the Rocket</title>
1449 In the rocket itself, you just need a <ulink url="http://www.altusmetrum.org/TeleMetrum/">TeleMetrum</ulink> or
1450 <ulink url="http://www.altusmetrum.org/TeleMini/">TeleMini</ulink> board and
1451 a single-cell, 3.7 volt nominal Li-Po rechargeable battery. An
1452 850mAh battery weighs less than a 9V alkaline battery, and will
1453 run a TeleMetrum for hours.
1454 A 110mAh battery weighs less than a triple A battery and will run a TeleMetrum for
1455 a few hours, or a TeleMini for much (much) longer.
1458 By default, we ship the altimeters with a simple wire antenna. If your
1459 electronics bay or the air-frame it resides within is made of carbon fiber,
1460 which is opaque to RF signals, you may choose to have an SMA connector
1461 installed so that you can run a coaxial cable to an antenna mounted
1462 elsewhere in the rocket.
1466 <title>On the Ground</title>
1468 To receive the data stream from the rocket, you need an antenna and short
1469 feed-line connected to one of our <ulink url="http://www.altusmetrum.org/TeleDongle/">TeleDongle</ulink> units. The
1470 TeleDongle in turn plugs directly into the USB port on a notebook
1471 computer. Because TeleDongle looks like a simple serial port, your computer
1472 does not require special device drivers... just plug it in.
1475 The GUI tool, AltosUI, is written in Java and runs across
1476 Linux, Mac OS and Windows. There's also a suite of C tools
1477 for Linux which can perform most of the same tasks.
1480 After the flight, you can use the radio link to extract the more detailed data
1481 logged in either TeleMetrum or TeleMini devices, or you can use a mini USB cable to plug into the
1482 TeleMetrum board directly. Pulling out the data without having to open up
1483 the rocket is pretty cool! A USB cable is also how you charge the Li-Po
1484 battery, so you'll want one of those anyway... the same cable used by lots
1485 of digital cameras and other modern electronic stuff will work fine.
1488 If your TeleMetrum-equipped rocket lands out of sight, you may enjoy having a hand-held GPS
1489 receiver, so that you can put in a way-point for the last reported rocket
1490 position before touch-down. This makes looking for your rocket a lot like
1491 Geo-Caching... just go to the way-point and look around starting from there.
1494 You may also enjoy having a ham radio "HT" that covers the 70cm band... you
1495 can use that with your antenna to direction-find the rocket on the ground
1496 the same way you can use a Walston or Beeline tracker. This can be handy
1497 if the rocket is hiding in sage brush or a tree, or if the last GPS position
1498 doesn't get you close enough because the rocket dropped into a canyon, or
1499 the wind is blowing it across a dry lake bed, or something like that... Keith
1500 and Bdale both currently own and use the Yaesu VX-7R at launches.
1503 So, to recap, on the ground the hardware you'll need includes:
1504 <orderedlist inheritnum='inherit' numeration='arabic'>
1506 an antenna and feed-line
1515 optionally, a hand-held GPS receiver
1518 optionally, an HT or receiver covering 435 MHz
1523 The best hand-held commercial directional antennas we've found for radio
1524 direction finding rockets are from
1525 <ulink url="http://www.arrowantennas.com/" >
1528 The 440-3 and 440-5 are both good choices for finding a
1529 TeleMetrum- or TeleMini- equipped rocket when used with a suitable 70cm HT.
1533 <title>Data Analysis</title>
1535 Our software makes it easy to log the data from each flight, both the
1536 telemetry received during the flight itself, and the more
1537 complete data log recorded in the flash memory on the altimeter
1538 board. Once this data is on your computer, our post-flight tools make it
1539 easy to quickly get to the numbers everyone wants, like apogee altitude,
1540 max acceleration, and max velocity. You can also generate and view a
1541 standard set of plots showing the altitude, acceleration, and
1542 velocity of the rocket during flight. And you can even export a TeleMetrum data file
1543 usable with Google Maps and Google Earth for visualizing the flight path
1544 in two or three dimensions!
1547 Our ultimate goal is to emit a set of files for each flight that can be
1548 published as a web page per flight, or just viewed on your local disk with
1553 <title>Future Plans</title>
1555 In the future, we intend to offer "companion boards" for the rocket that will
1556 plug in to TeleMetrum to collect additional data, provide more pyro channels,
1560 We are also working on the design of a hand-held ground terminal that will
1561 allow monitoring the rocket's status, collecting data during flight, and
1562 logging data after flight without the need for a notebook computer on the
1563 flight line. Particularly since it is so difficult to read most notebook
1564 screens in direct sunlight, we think this will be a great thing to have.
1567 Because all of our work is open, both the hardware designs and the software,
1568 if you have some great idea for an addition to the current Altus Metrum family,
1569 feel free to dive in and help! Or let us know what you'd like to see that
1570 we aren't already working on, and maybe we'll get excited about it too...
1575 <title>Altimeter Installation Recommendations</title>
1577 Building high-power rockets that fly safely is hard enough. Mix
1578 in some sophisticated electronics and a bunch of radio energy
1579 and oftentimes you find few perfect solutions. This chapter
1580 contains some suggestions about how to install Altus Metrum
1581 products into the rocket air-frame, including how to safely and
1582 reliably mix a variety of electronics into the same air-frame.
1585 <title>Mounting the Altimeter</title>
1587 The first consideration is to ensure that the altimeter is
1588 securely fastened to the air-frame. For TeleMetrum, we use
1589 nylon standoffs and nylon screws; they're good to at least 50G
1590 and cannot cause any electrical issues on the board. For
1591 TeleMini, we usually cut small pieces of 1/16" balsa to fit
1592 under the screw holes, and then take 2x56 nylon screws and
1593 screw them through the TeleMini mounting holes, through the
1594 balsa and into the underlying material.
1596 <orderedlist inheritnum='inherit' numeration='arabic'>
1598 Make sure TeleMetrum is aligned precisely along the axis of
1599 acceleration so that the accelerometer can accurately
1600 capture data during the flight.
1603 Watch for any metal touching components on the
1604 board. Shorting out connections on the bottom of the board
1605 can cause the altimeter to fail during flight.
1610 <title>Dealing with the Antenna</title>
1612 The antenna supplied is just a piece of solid, insulated,
1613 wire. If it gets damaged or broken, it can be easily
1614 replaced. It should be kept straight and not cut; bending or
1615 cutting it will change the resonant frequency and/or
1616 impedance, making it a less efficient radiator and thus
1617 reducing the range of the telemetry signal.
1620 Keeping metal away from the antenna will provide better range
1621 and a more even radiation pattern. In most rockets, it's not
1622 entirely possible to isolate the antenna from metal
1623 components; there are often bolts, all-thread and wires from other
1624 electronics to contend with. Just be aware that the more stuff
1625 like this around the antenna, the lower the range.
1628 Make sure the antenna is not inside a tube made or covered
1629 with conducting material. Carbon fiber is the most common
1630 culprit here -- CF is a good conductor and will effectively
1631 shield the antenna, dramatically reducing signal strength and
1632 range. Metallic flake paint is another effective shielding
1633 material which is to be avoided around any antennas.
1636 If the ebay is large enough, it can be convenient to simply
1637 mount the altimeter at one end and stretch the antenna out
1638 inside. Taping the antenna to the sled can keep it straight
1639 under acceleration. If there are metal rods, keep the
1640 antenna as far away as possible.
1643 For a shorter ebay, it's quite practical to have the antenna
1644 run through a bulkhead and into an adjacent bay. Drill a small
1645 hole in the bulkhead, pass the antenna wire through it and
1646 then seal it up with glue or clay. We've also used acrylic
1647 tubing to create a cavity for the antenna wire. This works a
1648 bit better in that the antenna is known to stay straight and
1649 not get folded by recovery components in the bay. Angle the
1650 tubing towards the side wall of the rocket and it ends up
1651 consuming very little space.
1654 If you need to place the antenna at a distance from the
1655 altimeter, you can replace the antenna with an edge-mounted
1656 SMA connector, and then run 50Ω coax from the board to the
1657 antenna. Building a remote antenna is beyond the scope of this
1662 <title>Preserving GPS Reception</title>
1664 The GPS antenna and receiver in TeleMetrum are highly
1665 sensitive and normally have no trouble tracking enough
1666 satellites to provide accurate position information for
1667 recovering the rocket. However, there are many ways to
1668 attenuate the GPS signal.
1669 <orderedlist inheritnum='inherit' numeration='arabic'>
1671 Conductive tubing or coatings. Carbon fiber and metal
1672 tubing, or metallic paint will all dramatically attenuate the
1673 GPS signal. We've never heard of anyone successfully
1674 receiving GPS from inside these materials.
1677 Metal components near the GPS patch antenna. These will
1678 de-tune the patch antenna, changing the resonant frequency
1679 away from the L1 carrier and reduce the effectiveness of the
1680 antenna. You can place as much stuff as you like beneath the
1681 antenna as that's covered with a ground plane. But, keep
1682 wires and metal out from above the patch antenna.
1688 <title>Radio Frequency Interference</title>
1690 Any altimeter will generate RFI; the digital circuits use
1691 high-frequency clocks that spray radio interference across a
1692 wide band. Altus Metrum altimeters generate intentional radio
1693 signals as well, increasing the amount of RF energy around the board.
1696 Rocketry altimeters also use precise sensors measuring air
1697 pressure and acceleration. Tiny changes in voltage can cause
1698 these sensor readings to vary by a huge amount. When the
1699 sensors start mis-reporting data, the altimeter can either
1700 fire the igniters at the wrong time, or not fire them at all.
1703 Voltages are induced when radio frequency energy is
1704 transmitted from one circuit to another. Here are things that
1705 influence the induced voltage and current:
1709 Keep wires from different circuits apart. Moving circuits
1710 further apart will reduce RFI.
1713 Avoid parallel wires from different circuits. The longer two
1714 wires run parallel to one another, the larger the amount of
1715 transferred energy. Cross wires at right angles to reduce
1719 Twist wires from the same circuits. Two wires the same
1720 distance from the transmitter will get the same amount of
1721 induced energy which will then cancel out. Any time you have
1722 a wire pair running together, twist the pair together to
1723 even out distances and reduce RFI. For altimeters, this
1724 includes battery leads, switch hookups and igniter
1728 Avoid resonant lengths. Know what frequencies are present
1729 in the environment and avoid having wire lengths near a
1730 natural resonant length. Altusmetrum products transmit on the
1731 70cm amateur band, so you should avoid lengths that are a
1732 simple ratio of that length; essentially any multiple of 1/4
1733 of the wavelength (17.5cm).
1738 <title>The Barometric Sensor</title>
1740 Altusmetrum altimeters measure altitude with a barometric
1741 sensor, essentially measuring the amount of air above the
1742 rocket to figure out how high it is. A large number of
1743 measurements are taken as the altimeter initializes itself to
1744 figure out the pad altitude. Subsequent measurements are then
1745 used to compute the height above the pad.
1748 To accurately measure atmospheric pressure, the ebay
1749 containing the altimeter must be vented outside the
1750 air-frame. The vent must be placed in a region of linear
1751 airflow, have smooth edges, and away from areas of increasing or
1752 decreasing pressure.
1755 The barometric sensor in the altimeter is quite sensitive to
1756 chemical damage from the products of APCP or BP combustion, so
1757 make sure the ebay is carefully sealed from any compartment
1758 which contains ejection charges or motors.
1762 <title>Ground Testing</title>
1764 The most important aspect of any installation is careful
1765 ground testing. Bringing an air-frame up to the LCO table which
1766 hasn't been ground tested can lead to delays or ejection
1767 charges firing on the pad, or, even worse, a recovery system
1771 Do a 'full systems' test that includes wiring up all igniters
1772 without any BP and turning on all of the electronics in flight
1773 mode. This will catch any mistakes in wiring and any residual
1774 RFI issues that might accidentally fire igniters at the wrong
1775 time. Let the air-frame sit for several minutes, checking for
1776 adequate telemetry signal strength and GPS lock. If any igniters
1777 fire unexpectedly, find and resolve the issue before loading any
1781 Ground test the ejection charges. Prepare the rocket for
1782 flight, loading ejection charges and igniters. Completely
1783 assemble the air-frame and then use the 'Fire Igniters'
1784 interface through a TeleDongle to command each charge to
1785 fire. Make sure the charge is sufficient to robustly separate
1786 the air-frame and deploy the recovery system.
1791 <title>Updating Device Firmware</title>
1793 The big concept to understand is that you have to use a
1794 TeleDongle as a programmer to update a TeleMetrum or TeleMini,
1795 and a TeleMetrum or other TeleDongle to program the TeleDongle
1796 Due to limited memory resources in the cc1111, we don't support
1797 programming directly over USB.
1800 You may wish to begin by ensuring you have current firmware images.
1801 These are distributed as part of the AltOS software bundle that
1802 also includes the AltosUI ground station program. Newer ground
1803 station versions typically work fine with older firmware versions,
1804 so you don't need to update your devices just to try out new
1805 software features. You can always download the most recent
1806 version from <ulink url="http://www.altusmetrum.org/AltOS/"/>.
1809 We recommend updating the altimeter first, before updating TeleDongle.
1812 <title>Updating TeleMetrum Firmware</title>
1813 <orderedlist inheritnum='inherit' numeration='arabic'>
1815 Find the 'programming cable' that you got as part of the starter
1816 kit, that has a red 8-pin MicroMaTch connector on one end and a
1817 red 4-pin MicroMaTch connector on the other end.
1820 Take the 2 screws out of the TeleDongle case to get access
1821 to the circuit board.
1824 Plug the 8-pin end of the programming cable to the
1825 matching connector on the TeleDongle, and the 4-pin end to the
1826 matching connector on the TeleMetrum.
1827 Note that each MicroMaTch connector has an alignment pin that
1828 goes through a hole in the PC board when you have the cable
1832 Attach a battery to the TeleMetrum board.
1835 Plug the TeleDongle into your computer's USB port, and power
1839 Run AltosUI, and select 'Flash Image' from the File menu.
1842 Pick the TeleDongle device from the list, identifying it as the
1846 Select the image you want put on the TeleMetrum, which should have a
1847 name in the form telemetrum-v1.2-1.0.0.ihx. It should be visible
1848 in the default directory, if not you may have to poke around
1849 your system to find it.
1852 Make sure the configuration parameters are reasonable
1853 looking. If the serial number and/or RF configuration
1854 values aren't right, you'll need to change them.
1857 Hit the 'OK' button and the software should proceed to flash
1858 the TeleMetrum with new firmware, showing a progress bar.
1861 Confirm that the TeleMetrum board seems to have updated OK, which you
1862 can do by plugging in to it over USB and using a terminal program
1863 to connect to the board and issue the 'v' command to check
1867 If something goes wrong, give it another try.
1872 <title>Updating TeleMini Firmware</title>
1873 <orderedlist inheritnum='inherit' numeration='arabic'>
1875 You'll need a special 'programming cable' to reprogram the
1876 TeleMini. It's available on the Altus Metrum web store, or
1877 you can make your own using an 8-pin MicroMaTch connector on
1878 one end and a set of four pins on the other.
1881 Take the 2 screws out of the TeleDongle case to get access
1882 to the circuit board.
1885 Plug the 8-pin end of the programming cable to the matching
1886 connector on the TeleDongle, and the 4-pins into the holes
1887 in the TeleMini circuit board. Note that the MicroMaTch
1888 connector has an alignment pin that goes through a hole in
1889 the PC board when you have the cable oriented correctly, and
1890 that pin 1 on the TeleMini board is marked with a square pad
1891 while the other pins have round pads.
1894 Attach a battery to the TeleMini board.
1897 Plug the TeleDongle into your computer's USB port, and power
1901 Run AltosUI, and select 'Flash Image' from the File menu.
1904 Pick the TeleDongle device from the list, identifying it as the
1908 Select the image you want put on the TeleMini, which should have a
1909 name in the form telemini-v1.0-1.0.0.ihx. It should be visible
1910 in the default directory, if not you may have to poke around
1911 your system to find it.
1914 Make sure the configuration parameters are reasonable
1915 looking. If the serial number and/or RF configuration
1916 values aren't right, you'll need to change them.
1919 Hit the 'OK' button and the software should proceed to flash
1920 the TeleMini with new firmware, showing a progress bar.
1923 Confirm that the TeleMini board seems to have updated OK, which you
1924 can do by configuring it over the radio link through the TeleDongle, or
1925 letting it come up in "flight" mode and listening for telemetry.
1928 If something goes wrong, give it another try.
1933 <title>Updating TeleDongle Firmware</title>
1935 Updating TeleDongle's firmware is just like updating TeleMetrum or TeleMini
1936 firmware, but you use either a TeleMetrum or another TeleDongle as the programmer.
1938 <orderedlist inheritnum='inherit' numeration='arabic'>
1940 Find the 'programming cable' that you got as part of the starter
1941 kit, that has a red 8-pin MicroMaTch connector on one end and a
1942 red 4-pin MicroMaTch connector on the other end.
1945 Find the USB cable that you got as part of the starter kit, and
1946 plug the "mini" end in to the mating connector on TeleMetrum or TeleDongle.
1949 Take the 2 screws out of the TeleDongle case to get access
1950 to the circuit board.
1953 Plug the 8-pin end of the programming cable to the
1954 matching connector on the programmer, and the 4-pin end to the
1955 matching connector on the TeleDongle.
1956 Note that each MicroMaTch connector has an alignment pin that
1957 goes through a hole in the PC board when you have the cable
1961 Attach a battery to the TeleMetrum board if you're using one.
1964 Plug both the programmer and the TeleDongle into your computer's USB
1965 ports, and power up the programmer.
1968 Run AltosUI, and select 'Flash Image' from the File menu.
1971 Pick the programmer device from the list, identifying it as the
1975 Select the image you want put on the TeleDongle, which should have a
1976 name in the form teledongle-v0.2-1.0.0.ihx. It should be visible
1977 in the default directory, if not you may have to poke around
1978 your system to find it.
1981 Make sure the configuration parameters are reasonable
1982 looking. If the serial number and/or RF configuration
1983 values aren't right, you'll need to change them. The TeleDongle
1984 serial number is on the "bottom" of the circuit board, and can
1985 usually be read through the translucent blue plastic case without
1986 needing to remove the board from the case.
1989 Hit the 'OK' button and the software should proceed to flash
1990 the TeleDongle with new firmware, showing a progress bar.
1993 Confirm that the TeleDongle board seems to have updated OK, which you
1994 can do by plugging in to it over USB and using a terminal program
1995 to connect to the board and issue the 'v' command to check
1996 the version, etc. Once you're happy, remove the programming cable
1997 and put the cover back on the TeleDongle.
2000 If something goes wrong, give it another try.
2004 Be careful removing the programming cable from the locking 8-pin
2005 connector on TeleMetrum. You'll need a fingernail or perhaps a thin
2006 screwdriver or knife blade to gently pry the locking ears out
2007 slightly to extract the connector. We used a locking connector on
2008 TeleMetrum to help ensure that the cabling to companion boards
2009 used in a rocket don't ever come loose accidentally in flight.
2014 <title>Hardware Specifications</title>
2016 <title>TeleMetrum Specifications</title>
2020 Recording altimeter for model rocketry.
2025 Supports dual deployment (can fire 2 ejection charges).
2030 70cm ham-band transceiver for telemetry down-link.
2035 Barometric pressure sensor good to 45k feet MSL.
2040 1-axis high-g accelerometer for motor characterization, capable of
2041 +/- 50g using default part.
2046 On-board, integrated GPS receiver with 5Hz update rate capability.
2051 On-board 1 megabyte non-volatile memory for flight data storage.
2056 USB interface for battery charging, configuration, and data recovery.
2061 Fully integrated support for Li-Po rechargeable batteries.
2066 Uses Li-Po to fire e-matches, can be modified to support
2067 optional separate pyro battery if needed.
2072 2.75 x 1 inch board designed to fit inside 29mm air-frame coupler tube.
2078 <title>TeleMini Specifications</title>
2082 Recording altimeter for model rocketry.
2087 Supports dual deployment (can fire 2 ejection charges).
2092 70cm ham-band transceiver for telemetry down-link.
2097 Barometric pressure sensor good to 45k feet MSL.
2102 On-board 5 kilobyte non-volatile memory for flight data storage.
2107 RF interface for battery charging, configuration, and data recovery.
2112 Support for Li-Po rechargeable batteries, using an external charger.
2117 Uses Li-Po to fire e-matches, can be modified to support
2118 optional separate pyro battery if needed.
2123 1.5 x .5 inch board designed to fit inside 18mm air-frame coupler tube.
2132 TeleMetrum seems to shut off when disconnected from the
2133 computer. Make sure the battery is adequately charged. Remember the
2134 unit will pull more power than the USB port can deliver before the
2135 GPS enters "locked" mode. The battery charges best when TeleMetrum
2139 It's impossible to stop the TeleDongle when it's in "p" mode, I have
2140 to unplug the USB cable? Make sure you have tried to "escape out" of
2141 this mode. If this doesn't work the reboot procedure for the
2142 TeleDongle *is* to simply unplug it. 'cu' however will retain it's
2143 outgoing buffer IF your "escape out" ('~~') does not work.
2144 At this point using either 'ao-view' (or possibly
2145 'cutemon') instead of 'cu' will 'clear' the issue and allow renewed
2149 The amber LED (on the TeleMetrum) lights up when both
2150 battery and USB are connected. Does this mean it's charging?
2151 Yes, the yellow LED indicates the charging at the 'regular' rate.
2152 If the led is out but the unit is still plugged into a USB port,
2153 then the battery is being charged at a 'trickle' rate.
2156 There are no "dit-dah-dah-dit" sound or lights like the manual mentions?
2157 That's the "pad" mode. Weak batteries might be the problem.
2158 It is also possible that the TeleMetrum is horizontal and the output
2159 is instead a "dit-dit" meaning 'idle'. For TeleMini, it's possible that
2160 it received a command packet which would have left it in "pad" mode.
2163 How do I save flight data?
2164 Live telemetry is written to file(s) whenever AltosUI is connected
2165 to the TeleDongle. The file area defaults to ~/TeleMetrum
2166 but is easily changed using the menus in AltosUI. The files that
2167 are written end in '.telem'. The after-flight
2168 data-dumped files will end in .eeprom and represent continuous data
2169 unlike the .telem files that are subject to losses
2170 along the RF data path.
2171 See the above instructions on what and how to save the eeprom stored
2172 data after physically retrieving your altimeter. Make sure to save
2173 the on-board data after each flight; while the TeleMetrum can store
2174 multiple flights, you never know when you'll lose the altimeter...
2178 <title>Notes for Older Software</title>
2181 Before AltosUI was written, using Altus Metrum devices required
2182 some finesse with the Linux command line. There was a limited
2183 GUI tool, ao-view, which provided functionality similar to the
2184 Monitor Flight window in AltosUI, but everything else was a
2185 fairly 80's experience. This appendix includes documentation for
2186 using that software.
2190 Both TeleMetrum and TeleDongle can be directly communicated
2191 with using USB ports. The first thing you should try after getting
2192 both units plugged into to your computer's USB port(s) is to run
2193 'ao-list' from a terminal-window to see what port-device-name each
2194 device has been assigned by the operating system.
2195 You will need this information to access the devices via their
2196 respective on-board firmware and data using other command line
2197 programs in the AltOS software suite.
2200 TeleMini can be communicated with through a TeleDongle device
2201 over the radio link. When first booted, TeleMini listens for a
2202 TeleDongle device and if it receives a packet, it goes into
2203 'idle' mode. Otherwise, it goes into 'pad' mode and waits to be
2204 launched. The easiest way to get it talking is to start the
2205 communication link on the TeleDongle and the power up the
2209 To access the device's firmware for configuration you need a terminal
2210 program such as you would use to talk to a modem. The software
2211 authors prefer using the program 'cu' which comes from the UUCP package
2212 on most Unix-like systems such as Linux. An example command line for
2213 cu might be 'cu -l /dev/ttyACM0', substituting the correct number
2214 indicated from running the
2215 ao-list program. Another reasonable terminal program for Linux is
2216 'cutecom'. The default 'escape'
2217 character used by CU (i.e. the character you use to
2218 issue commands to cu itself instead of sending the command as input
2219 to the connected device) is a '~'. You will need this for use in
2220 only two different ways during normal operations. First is to exit
2221 the program by sending a '~.' which is called a 'escape-disconnect'
2222 and allows you to close-out from 'cu'. The
2223 second use will be outlined later.
2226 All of the Altus Metrum devices share the concept of a two level
2227 command set in their firmware.
2228 The first layer has several single letter commands. Once
2229 you are using 'cu' (or 'cutecom') sending (typing) a '?'
2230 returns a full list of these
2231 commands. The second level are configuration sub-commands accessed
2232 using the 'c' command, for
2233 instance typing 'c?' will give you this second level of commands
2234 (all of which require the
2235 letter 'c' to access). Please note that most configuration options
2236 are stored only in Flash memory; TeleDongle doesn't provide any storage
2237 for these options and so they'll all be lost when you unplug it.
2240 Try setting these configuration ('c' or second level menu) values. A good
2241 place to start is by setting your call sign. By default, the boards
2242 use 'N0CALL' which is cute, but not exactly legal!
2243 Spend a few minutes getting comfortable with the units, their
2244 firmware, and 'cu' (or possibly 'cutecom').
2245 For instance, try to send
2246 (type) a 'c r 2' and verify the channel change by sending a 'c s'.
2247 Verify you can connect and disconnect from the units while in your
2248 terminal program by sending the escape-disconnect mentioned above.
2251 To set the radio frequency, use the 'c R' command to specify the
2252 radio transceiver configuration parameter. This parameter is computed
2253 using the desired frequency, 'F', the radio calibration parameter, 'C' (showed by the 'c s' command) and
2254 the standard calibration reference frequency, 'S', (normally 434.550MHz):
2258 Round the result to the nearest integer value.
2259 As with all 'c' sub-commands, follow this with a 'c w' to write the
2260 change to the parameter block in the on-board flash on
2261 your altimeter board if you want the change to stay in place across reboots.
2264 To set the apogee delay, use the 'c d' command.
2265 As with all 'c' sub-commands, follow this with a 'c w' to write the
2266 change to the parameter block in the on-board DataFlash chip.
2269 To set the main deployment altitude, use the 'c m' command.
2270 As with all 'c' sub-commands, follow this with a 'c w' to write the
2271 change to the parameter block in the on-board DataFlash chip.
2274 To calibrate the radio frequency, connect the UHF antenna port to a
2275 frequency counter, set the board to 434.550MHz, and use the 'C'
2276 command to generate a CW carrier. Wait for the transmitter temperature
2277 to stabilize and the frequency to settle down.
2278 Then, divide 434.550 MHz by the
2279 measured frequency and multiply by the current radio cal value show
2280 in the 'c s' command. For an unprogrammed board, the default value
2281 is 1186611. Take the resulting integer and program it using the 'c f'
2282 command. Testing with the 'C' command again should show a carrier
2283 within a few tens of Hertz of the intended frequency.
2284 As with all 'c' sub-commands, follow this with a 'c w' to write the
2285 change to the parameter block in the on-board DataFlash chip.
2288 Note that the 'reboot' command, which is very useful on the altimeters,
2289 will likely just cause problems with the dongle. The *correct* way
2290 to reset the dongle is just to unplug and re-plug it.
2293 A fun thing to do at the launch site and something you can do while
2294 learning how to use these units is to play with the radio link access
2295 between an altimeter and the TeleDongle. Be aware that you *must* create
2296 some physical separation between the devices, otherwise the link will
2297 not function due to signal overload in the receivers in each device.
2300 Now might be a good time to take a break and read the rest of this
2301 manual, particularly about the two "modes" that the altimeters
2302 can be placed in. TeleMetrum uses the position of the device when booting
2303 up will determine whether the unit is in "pad" or "idle" mode. TeleMini
2304 enters "idle" mode when it receives a command packet within the first 5 seconds
2305 of being powered up, otherwise it enters "pad" mode.
2308 You can access an altimeter in idle mode from the TeleDongle's USB
2309 connection using the radio link
2310 by issuing a 'p' command to the TeleDongle. Practice connecting and
2311 disconnecting ('~~' while using 'cu') from the altimeter. If
2312 you cannot escape out of the "p" command, (by using a '~~' when in
2313 CU) then it is likely that your kernel has issues. Try a newer version.
2316 Using this radio link allows you to configure the altimeter, test
2317 fire e-matches and igniters from the flight line, check pyro-match
2318 continuity and so forth. You can leave the unit turned on while it
2319 is in 'idle mode' and then place the
2320 rocket vertically on the launch pad, walk away and then issue a
2321 reboot command. The altimeter will reboot and start sending data
2322 having changed to the "pad" mode. If the TeleDongle is not receiving
2323 this data, you can disconnect 'cu' from the TeleDongle using the
2324 procedures mentioned above and THEN connect to the TeleDongle from
2325 inside 'ao-view'. If this doesn't work, disconnect from the
2326 TeleDongle, unplug it, and try again after plugging it back in.
2329 In order to reduce the chance of accidental firing of pyrotechnic
2330 charges, the command to fire a charge is intentionally somewhat
2331 difficult to type, and the built-in help is slightly cryptic to
2332 prevent accidental echoing of characters from the help text back at
2333 the board from firing a charge. The command to fire the apogee
2334 drogue charge is 'i DoIt drogue' and the command to fire the main
2335 charge is 'i DoIt main'.
2338 On TeleMetrum, the GPS will eventually find enough satellites, lock in on them,
2339 and 'ao-view' will both auditorily announce and visually indicate
2341 Now you can launch knowing that you have a good data path and
2342 good satellite lock for flight data and recovery. Remember
2343 you MUST tell ao-view to connect to the TeleDongle explicitly in
2344 order for ao-view to be able to receive data.
2347 The altimeters provide RDF (radio direction finding) tones on
2348 the pad, during descent and after landing. These can be used to
2349 locate the rocket using a directional antenna; the signal
2350 strength providing an indication of the direction from receiver to rocket.
2353 TeleMetrum also provides GPS tracking data, which can further simplify
2354 locating the rocket once it has landed. (The last good GPS data
2355 received before touch-down will be on the data screen of 'ao-view'.)
2358 Once you have recovered the rocket you can download the eeprom
2359 contents using either 'ao-dumplog' (or possibly 'ao-eeprom'), over
2360 either a USB cable or over the radio link using TeleDongle.
2361 And by following the man page for 'ao-postflight' you can create
2362 various data output reports, graphs, and even KML data to see the
2363 flight trajectory in Google-earth. (Moving the viewing angle making
2364 sure to connect the yellow lines while in Google-earth is the proper
2368 As for ao-view.... some things are in the menu but don't do anything
2369 very useful. The developers have stopped working on ao-view to focus
2370 on a new, cross-platform ground station program. So ao-view may or
2371 may not be updated in the future. Mostly you just use
2372 the Log and Device menus. It has a wonderful display of the incoming
2373 flight data and I am sure you will enjoy what it has to say to you
2374 once you enable the voice output!
2378 <title>Calibration</title>
2380 There are only two calibrations required for a TeleMetrum board, and
2381 only one for TeleDongle and TeleMini. All boards are shipped from
2382 the factory pre-calibrated, but the procedures are documented here
2383 in case they are ever needed. Re-calibration is not supported by
2384 AltosUI, you must connect to the board with a serial terminal program
2385 and interact directly with the on-board command interpreter to effect
2389 <title>Radio Frequency</title>
2391 The radio frequency is synthesized from a clock based on the 48 MHz
2392 crystal on the board. The actual frequency of this oscillator
2393 must be measured to generate a calibration constant. While our
2395 bandwidth is wide enough to allow boards to communicate even when
2396 their oscillators are not on exactly the same frequency, performance
2397 is best when they are closely matched.
2398 Radio frequency calibration requires a calibrated frequency counter.
2399 Fortunately, once set, the variation in frequency due to aging and
2400 temperature changes is small enough that re-calibration by customers
2401 should generally not be required.
2404 To calibrate the radio frequency, connect the UHF antenna port to a
2405 frequency counter, set the board to 434.550MHz, and use the 'C'
2406 command in the on-board command interpreter to generate a CW
2407 carrier. For TeleMetrum, this is best done over USB. For TeleMini,
2408 note that the only way to escape the 'C' command is via power cycle
2409 since the board will no longer be listening for commands once it
2410 starts generating a CW carrier.
2413 Wait for the transmitter temperature to stabilize and the frequency
2414 to settle down. Then, divide 434.550 MHz by the
2415 measured frequency and multiply by the current radio cal value show
2416 in the 'c s' command. For an unprogrammed board, the default value
2417 is 1186611. Take the resulting integer and program it using the 'c f'
2418 command. Testing with the 'C' command again should show a carrier
2419 within a few tens of Hertz of the intended frequency.
2420 As with all 'c' sub-commands, follow this with a 'c w' to write the
2421 change to the parameter block in the on-board DataFlash chip.
2424 Note that any time you re-do the radio frequency calibration, the
2425 radio frequency is reset to the default 434.550 Mhz. If you want
2426 to use another frequency, you will have to set that again after
2427 calibration is completed.
2431 <title>TeleMetrum Accelerometer</title>
2433 The TeleMetrum accelerometer we use has its own 5 volt power
2435 the output must be passed through a resistive voltage divider to match
2436 the input of our 3.3 volt ADC. This means that unlike the barometric
2437 sensor, the output of the acceleration sensor is not ratio-metric to
2438 the ADC converter, and calibration is required. Explicitly
2439 calibrating the accelerometers also allows us to load any device
2440 from a Freescale family that includes at least +/- 40g, 50g, 100g,
2441 and 200g parts. Using gravity,
2442 a simple 2-point calibration yields acceptable results capturing both
2443 the different sensitivities and ranges of the different accelerometer
2444 parts and any variation in power supply voltages or resistor values
2445 in the divider network.
2448 To calibrate the acceleration sensor, use the 'c a 0' command. You
2449 will be prompted to orient the board vertically with the UHF antenna
2450 up and press a key, then to orient the board vertically with the
2451 UHF antenna down and press a key. Note that the accuracy of this
2452 calibration depends primarily on how perfectly vertical and still
2453 the board is held during the cal process. As with all 'c'
2454 sub-commands, follow this with a 'c w' to write the
2455 change to the parameter block in the on-board DataFlash chip.
2458 The +1g and -1g calibration points are included in each telemetry
2459 frame and are part of the header stored in onboard flash to be
2460 downloaded after flight. We always store and return raw ADC
2461 samples for each sensor... so nothing is permanently "lost" or
2462 "damaged" if the calibration is poor.
2465 In the unlikely event an accel cal goes badly, it is possible
2466 that TeleMetrum may always come up in 'pad mode' and as such not be
2467 listening to either the USB or radio link. If that happens,
2468 there is a special hook in the firmware to force the board back
2469 in to 'idle mode' so you can re-do the cal. To use this hook, you
2470 just need to ground the SPI clock pin at power-on. This pin is
2471 available as pin 2 on the 8-pin companion connector, and pin 1 is
2472 ground. So either carefully install a fine-gauge wire jumper
2473 between the two pins closest to the index hole end of the 8-pin
2474 connector, or plug in the programming cable to the 8-pin connector
2475 and use a small screwdriver or similar to short the two pins closest
2476 to the index post on the 4-pin end of the programming cable, and
2477 power up the board. It should come up in 'idle mode' (two beeps),
2483 xmlns:xi="http://www.w3.org/2001/XInclude">
2484 <title>Release Notes</title>
2485 <xi:include href="release-notes-1.1.xsl" xpointer="xpointer(/article/*)"/>
2486 <xi:include href="release-notes-1.0.1.xsl" xpointer="xpointer(/article/*)"/>
2487 <xi:include href="release-notes-0.9.2.xsl" xpointer="xpointer(/article/*)"/>
2488 <xi:include href="release-notes-0.9.xsl" xpointer="xpointer(/article/*)"/>
2489 <xi:include href="release-notes-0.8.xsl" xpointer="xpointer(/article/*)"/>
2490 <xi:include href="release-notes-0.7.1.xsl" xpointer="xpointer(/article/*)"/>
2494 <!-- LocalWords: Altusmetrum
projects / fw / altos / blob