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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.
264 By default, we use the unregulated output of the Li-Po battery directly
265 to fire ejection charges. This works marvelously with standard
266 low-current e-matches like the J-Tek from MJG Technologies, and with
267 Quest Q2G2 igniters. However, if you want or need to use a separate
268 pyro battery, check out the "External Pyro Battery" section in this
269 manual for instructions on how to wire that up. The altimeters are
270 designed to work with an external pyro battery of no more than 15 volts.
273 Ejection charges are wired directly to the screw terminal block
274 at the aft end of the altimeter. You'll need a very small straight
275 blade screwdriver for these screws, such as you might find in a
276 jeweler's screwdriver set.
279 TeleMetrum also uses the screw terminal block for the power
280 switch leads. On TeleMini, the power switch leads are soldered
281 directly to the board and can be connected directly to a switch.
284 For most air-frames, the integrated antennas are more than
285 adequate. However, if you are installing in a carbon-fiber or
286 metal electronics bay which is opaque to RF signals, you may need to
287 use off-board external antennas instead. In this case, you can
288 order an altimeter with an SMA connector for the UHF antenna
289 connection, and, on TeleMetrum, you can unplug the integrated GPS
290 antenna and select an appropriate off-board GPS antenna with
291 cable terminating in a U.FL connector.
295 <title>System Operation</title>
297 <title>Firmware Modes </title>
299 The AltOS firmware build for the altimeters has two
300 fundamental modes, "idle" and "flight". Which of these modes
301 the firmware operates in is determined at start up time. For
302 TeleMetrum, the mode is controlled by the orientation of the
303 rocket (well, actually the board, of course...) at the time
304 power is switched on. If the rocket is "nose up", then
305 TeleMetrum assumes it's on a rail or rod being prepared for
306 launch, so the firmware chooses flight mode. However, if the
307 rocket is more or less horizontal, the firmware instead enters
308 idle mode. Since TeleMini doesn't have an accelerometer we can
309 use to determine orientation, "idle" mode is selected when the
310 board receives a command packet within the first five seconds
311 of operation; if no packet is received, the board enters
315 At power on, you will hear three beeps or see three flashes
316 ("S" in Morse code for start up) and then a pause while
317 the altimeter completes initialization and self test, and decides
318 which mode to enter next.
321 In flight or "pad" mode, the altimeter engages the flight
322 state machine, goes into transmit-only mode to
323 send telemetry, and waits for launch to be detected.
324 Flight mode is indicated by an "di-dah-dah-dit" ("P" for pad)
325 on the beeper or lights, followed by beeps or flashes
326 indicating the state of the pyrotechnic igniter continuity.
327 One beep/flash indicates apogee continuity, two beeps/flashes
328 indicate main continuity, three beeps/flashes indicate both
329 apogee and main continuity, and one longer "brap" sound or
330 rapidly alternating lights indicates no continuity. For a
331 dual deploy flight, make sure you're getting three beeps or
332 flashes before launching! For apogee-only or motor eject
333 flights, do what makes sense.
336 If idle mode is entered, you will hear an audible "di-dit" or see
337 two short flashes ("I" for idle), and the flight state machine is
338 disengaged, thus no ejection charges will fire. The altimeters also
339 listen for the radio link when in idle mode for requests sent via
340 TeleDongle. Commands can be issued to a TeleMetrum in idle mode
342 USB or the radio link equivalently. TeleMini only has the radio link.
343 Idle mode is useful for configuring the altimeter, for extracting data
344 from the on-board storage chip after flight, and for ground testing
348 One "neat trick" of particular value when TeleMetrum is used with
349 very large air-frames, is that you can power the board up while the
350 rocket is horizontal, such that it comes up in idle mode. Then you can
351 raise the air-frame to launch position, and issue a 'reset' command
352 via TeleDongle over the radio link to cause the altimeter to reboot and
353 come up in flight mode. This is much safer than standing on the top
354 step of a rickety step-ladder or hanging off the side of a launch
355 tower with a screw-driver trying to turn on your avionics before
362 TeleMetrum includes a complete GPS receiver. A complete explanation
363 of how GPS works is beyond the scope of this manual, but the bottom
364 line is that the TeleMetrum GPS receiver needs to lock onto at least
365 four satellites to obtain a solid 3 dimensional position fix and know
369 TeleMetrum provides backup power to the GPS chip any time a
370 battery is connected. This allows the receiver to "warm start" on
371 the launch rail much faster than if every power-on were a GPS
372 "cold start". In typical operations, powering up TeleMetrum
373 on the flight line in idle mode while performing final air-frame
374 preparation will be sufficient to allow the GPS receiver to cold
375 start and acquire lock. Then the board can be powered down during
376 RSO review and installation on a launch rod or rail. When the board
377 is turned back on, the GPS system should lock very quickly, typically
378 long before igniter installation and return to the flight line are
383 <title>Controlling An Altimeter Over The Radio Link</title>
385 One of the unique features of the Altus Metrum system is
386 the ability to create a two way command link between TeleDongle
387 and an altimeter using the digital radio transceivers built into
388 each device. This allows you to interact with the altimeter from
389 afar, as if it were directly connected to the computer.
392 Any operation which can be performed with TeleMetrum can
393 either be done with TeleMetrum directly connected to the
394 computer via the USB cable, or through the radio
395 link. TeleMini doesn't provide a USB connector and so it is
396 always communicated with over radio. Select the appropriate
397 TeleDongle device when the list of devices is presented and
398 AltosUI will interact with an altimeter over the radio link.
401 One oddity in the current interface is how AltosUI selects the
402 frequency for radio communications. Instead of providing
403 an interface to specifically configure the frequency, it uses
404 whatever frequency was most recently selected for the target
405 TeleDongle device in Monitor Flight mode. If you haven't ever
406 used that mode with the TeleDongle in question, select the
407 Monitor Flight button from the top level UI, and pick the
408 appropriate TeleDongle device. Once the flight monitoring
409 window is open, select the desired frequency and then close it
410 down again. All radio communications will now use that frequency.
415 Save Flight Data—Recover flight data from the rocket without
421 Configure altimeter apogee delays or main deploy heights
422 to respond to changing launch conditions. You can also
423 'reboot' the altimeter. Use this to remotely enable the
424 flight computer by turning TeleMetrum on in "idle" mode,
425 then once the air-frame is oriented for launch, you can
426 reboot the altimeter and have it restart in pad mode
427 without having to climb the scary ladder.
432 Fire Igniters—Test your deployment charges without snaking
433 wires out through holes in the air-frame. Simply assembly the
434 rocket as if for flight with the apogee and main charges
435 loaded, then remotely command the altimeter to fire the
441 Operation over the radio link for configuring an altimeter, ground
442 testing igniters, and so forth uses the same RF frequencies as flight
443 telemetry. To configure the desired TeleDongle frequency, select
444 the monitor flight tab, then use the frequency selector and
445 close the window before performing other desired radio operations.
448 TeleMetrum only enables radio commanding in 'idle' mode, so
449 make sure you have TeleMetrum lying horizontally when you turn
450 it on. Otherwise, TeleMetrum will start in 'pad' mode ready for
451 flight, and will not be listening for command packets from TeleDongle.
454 TeleMini listens for a command packet for five seconds after
455 first being turned on, if it doesn't hear anything, it enters
456 'pad' mode, ready for flight and will no longer listen for
457 command packets. The easiest way to connect to TeleMini is to
458 initiate the command and select the TeleDongle device. At this
459 point, the TeleDongle will be attempting to communicate with
460 the TeleMini. Now turn TeleMini on, and it should immediately
461 start communicating with the TeleDongle and the desired
462 operation can be performed.
465 You can monitor the operation of the radio link by watching the
466 lights on the devices. The red LED will flash each time a packet
467 is tramsitted, while the green LED will light up on TeleDongle when
468 it is waiting to receive a packet from the altimeter.
472 <title>Ground Testing </title>
474 An important aspect of preparing a rocket using electronic deployment
475 for flight is ground testing the recovery system. Thanks
476 to the bi-directional radio link central to the Altus Metrum system,
477 this can be accomplished in a TeleMetrum or TeleMini equipped rocket
478 with less work than you may be accustomed to with other systems. It
482 Just prep the rocket for flight, then power up the altimeter
483 in "idle" mode (placing air-frame horizontal for TeleMetrum or
484 selected the Configure Altimeter tab for TeleMini). This will cause
485 the firmware to go into "idle" mode, in which the normal flight
486 state machine is disabled and charges will not fire without
487 manual command. You can now command the altimeter to fire the apogee
488 or main charges from a safe distance using your computer and
489 TeleDongle and the Fire Igniter tab to complete ejection testing.
493 <title>Radio Link </title>
495 The chip our boards are based on incorporates an RF transceiver, but
496 it's not a full duplex system... each end can only be transmitting or
497 receiving at any given moment. So we had to decide how to manage the
501 By design, the altimeter firmware listens for the radio link when
502 it's in "idle mode", which
503 allows us to use the radio link to configure the rocket, do things like
504 ejection tests, and extract data after a flight without having to
505 crack open the air-frame. However, when the board is in "flight
506 mode", the altimeter only
507 transmits and doesn't listen at all. That's because we want to put
508 ultimate priority on event detection and getting telemetry out of
510 the radio in case the rocket crashes and we aren't able to extract
514 We don't use a 'normal packet radio' mode like APRS because they're
515 just too inefficient. The GFSK modulation we use is FSK with the
516 base-band pulses passed through a
517 Gaussian filter before they go into the modulator to limit the
518 transmitted bandwidth. When combined with the hardware forward error
519 correction support in the cc1111 chip, this allows us to have a very
520 robust 38.4 kilobit data link with only 10 milliwatts of transmit
521 power, a whip antenna in the rocket, and a hand-held Yagi on the
522 ground. We've had flights to above 21k feet AGL with great reception,
523 and calculations suggest we should be good to well over 40k feet AGL
524 with a 5-element yagi on the ground. We hope to fly boards to higher
525 altitudes over time, and would of course appreciate customer feedback
526 on performance in higher altitude flights!
530 <title>Configurable Parameters</title>
532 Configuring an Altus Metrum altimeter for flight is very
533 simple. Even on our baro-only TeleMini board, the use of a Kalman
534 filter means there is no need to set a "mach delay". The few
535 configurable parameters can all be set using AltosUI over USB or
536 or radio link via TeleDongle.
539 <title>Radio Frequency</title>
541 Altus Metrum boards support radio frequencies in the 70cm
542 band. By default, the configuration interface provides a
543 list of 10 "standard" frequencies in 100kHz channels starting at
544 434.550MHz. However, the firmware supports use of
545 any 50kHz multiple within the 70cm band. At any given
546 launch, we highly recommend coordinating when and by whom each
547 frequency will be used to avoid interference. And of course, both
548 altimeter and TeleDongle must be configured to the same
549 frequency to successfully communicate with each other.
553 <title>Apogee Delay</title>
555 Apogee delay is the number of seconds after the altimeter detects flight
556 apogee that the drogue charge should be fired. In most cases, this
557 should be left at the default of 0. However, if you are flying
558 redundant electronics such as for an L3 certification, you may wish
559 to set one of your altimeters to a positive delay so that both
560 primary and backup pyrotechnic charges do not fire simultaneously.
563 The Altus Metrum apogee detection algorithm fires exactly at
564 apogee. If you are also flying an altimeter like the
565 PerfectFlite MAWD, which only supports selecting 0 or 1
566 seconds of apogee delay, you may wish to set the MAWD to 0
567 seconds delay and set the TeleMetrum to fire your backup 2
568 or 3 seconds later to avoid any chance of both charges
569 firing simultaneously. We've flown several air-frames this
570 way quite happily, including Keith's successful L3 cert.
574 <title>Main Deployment Altitude</title>
576 By default, the altimeter will fire the main deployment charge at an
577 elevation of 250 meters (about 820 feet) above ground. We think this
578 is a good elevation for most air-frames, but feel free to change this
579 to suit. In particular, if you are flying two altimeters, you may
581 deployment elevation for the backup altimeter to be something lower
582 than the primary so that both pyrotechnic charges don't fire
587 <title>Maximum Flight Log</title>
589 TeleMetrum version 1.1 has 2MB of on-board flash storage,
590 enough to hold over 40 minutes of data at full data rate
591 (100 samples/second). TeleMetrum 1.0 has 1MB of on-board
592 storage. As data are stored at a reduced rate during descent
593 (10 samples/second), there's plenty of space to store many
594 flights worth of data.
597 The on-board flash is partitioned into separate flight logs,
598 each of a fixed maximum size. Increase the maximum size of
599 each log and you reduce the number of flights that can be
600 stored. Decrease the size and TeleMetrum can store more
604 All of the configuration data is also stored in the flash
605 memory, which consumes 64kB on TeleMetrum v1.1 and 256B on
606 TeleMetrum v1.0. This configuration space is not available
607 for storing flight log data.
610 To compute the amount of space needed for a single flight,
611 you can multiply the expected ascent time (in seconds) by
612 800, multiply the expected descent time (in seconds) by 80
613 and add the two together. That will slightly under-estimate
614 the storage (in bytes) needed for the flight. For instance,
615 a flight spending 20 seconds in ascent and 150 seconds in
616 descent will take about (20 * 800) + (150 * 80) = 28000
617 bytes of storage. You could store dozens of these flights in
621 The default size, 192kB, allows for 10 flights of storage on
622 TeleMetrum v1.1 and 5 flights on TeleMetrum v1.0. This
623 ensures that you won't need to erase the memory before
624 flying each time while still allowing more than sufficient
625 storage for each flight.
628 As TeleMini does not contain an accelerometer, it stores
629 data at 10 samples per second during ascent and one sample
630 per second during descent. Each sample is a two byte reading
631 from the barometer. These are stored in 5kB of
632 on-chip flash memory which can hold 256 seconds at the
633 ascent rate or 2560 seconds at the descent rate. Because of
634 the limited storage, TeleMini cannot hold data for more than
635 one flight, and so must be erased after each flight or it
636 will not capture data for subsequent flights.
640 <title>Ignite Mode</title>
642 Instead of firing one charge at apogee and another charge at
643 a fixed height above the ground, you can configure the
644 altimeter to fire both at apogee or both during
645 descent. This was added to support an airframe that has two
646 TeleMetrum computers, one in the fin can and one in the
650 Providing the ability to use both igniters for apogee or
651 main allows some level of redundancy without needing two
652 flight computers. In Redundant Apogee or Redundant Main
653 mode, the two charges will be fired two seconds apart.
657 <title>Pad Orientation</title>
659 TeleMetrum measures acceleration along the axis of the
660 board. Which way the board is oriented affects the sign of
661 the acceleration value. Instead of trying to guess which way
662 the board is mounted in the air frame, TeleMetrum must be
663 explicitly configured for either Antenna Up or Antenna
664 Down. The default, Antenna Up, expects the end of the
665 TeleMetrum board connected to the 70cm antenna to be nearest
666 the nose of the rocket, with the end containing the screw
667 terminals nearest the tail.
675 <title>AltosUI</title>
677 The AltosUI program provides a graphical user interface for
678 interacting with the Altus Metrum product family, including
679 TeleMetrum, TeleMini and TeleDongle. AltosUI can monitor telemetry data,
680 configure TeleMetrum, TeleMini and TeleDongle devices and many other
681 tasks. The primary interface window provides a selection of
682 buttons, one for each major activity in the system. This manual
683 is split into chapters, each of which documents one of the tasks
684 provided from the top-level toolbar.
687 <title>Monitor Flight</title>
688 <subtitle>Receive, Record and Display Telemetry Data</subtitle>
690 Selecting this item brings up a dialog box listing all of the
691 connected TeleDongle devices. When you choose one of these,
692 AltosUI will create a window to display telemetry data as
693 received by the selected TeleDongle device.
696 All telemetry data received are automatically recorded in
697 suitable log files. The name of the files includes the current
698 date and rocket serial and flight numbers.
701 The radio frequency being monitored by the TeleDongle device is
702 displayed at the top of the window. You can configure the
703 frequency by clicking on the frequency box and selecting the desired
704 frequency. AltosUI remembers the last frequency selected for each
705 TeleDongle and selects that automatically the next time you use
709 Below the TeleDongle frequency selector, the window contains a few
710 significant pieces of information about the altimeter providing
711 the telemetry data stream:
715 <para>The configured call-sign</para>
718 <para>The device serial number</para>
721 <para>The flight number. Each altimeter remembers how many
727 The rocket flight state. Each flight passes through several
728 states including Pad, Boost, Fast, Coast, Drogue, Main and
734 The Received Signal Strength Indicator value. This lets
735 you know how strong a signal TeleDongle is receiving. The
736 radio inside TeleDongle operates down to about -99dBm;
737 weaker signals may not be receivable. The packet link uses
738 error detection and correction techniques which prevent
739 incorrect data from being reported.
744 Finally, the largest portion of the window contains a set of
745 tabs, each of which contain some information about the rocket.
746 They're arranged in 'flight order' so that as the flight
747 progresses, the selected tab automatically switches to display
748 data relevant to the current state of the flight. You can select
749 other tabs at any time. The final 'table' tab displays all of
750 the raw telemetry values in one place in a spreadsheet-like format.
753 <title>Launch Pad</title>
755 The 'Launch Pad' tab shows information used to decide when the
756 rocket is ready for flight. The first elements include red/green
757 indicators, if any of these is red, you'll want to evaluate
758 whether the rocket is ready to launch:
762 Battery Voltage. This indicates whether the Li-Po battery
763 powering the TeleMetrum has sufficient charge to last for
764 the duration of the flight. A value of more than
765 3.7V is required for a 'GO' status.
770 Apogee Igniter Voltage. This indicates whether the apogee
771 igniter has continuity. If the igniter has a low
772 resistance, then the voltage measured here will be close
773 to the Li-Po battery voltage. A value greater than 3.2V is
774 required for a 'GO' status.
779 Main Igniter Voltage. This indicates whether the main
780 igniter has continuity. If the igniter has a low
781 resistance, then the voltage measured here will be close
782 to the Li-Po battery voltage. A value greater than 3.2V is
783 required for a 'GO' status.
788 On-board Data Logging. This indicates whether there is
789 space remaining on-board to store flight data for the
790 upcoming flight. If you've downloaded data, but failed
791 to erase flights, there may not be any space
792 left. TeleMetrum can store multiple flights, depending
793 on the configured maximum flight log size. TeleMini
794 stores only a single flight, so it will need to be
795 downloaded and erased after each flight to capture
796 data. This only affects on-board flight logging; the
797 altimeter will still transmit telemetry and fire
798 ejection charges at the proper times.
803 GPS Locked. For a TeleMetrum device, this indicates whether the GPS receiver is
804 currently able to compute position information. GPS requires
805 at least 4 satellites to compute an accurate position.
810 GPS Ready. For a TeleMetrum device, this indicates whether GPS has reported at least
811 10 consecutive positions without losing lock. This ensures
812 that the GPS receiver has reliable reception from the
818 The Launchpad tab also shows the computed launch pad position
819 and altitude, averaging many reported positions to improve the
825 <title>Ascent</title>
827 This tab is shown during Boost, Fast and Coast
828 phases. The information displayed here helps monitor the
829 rocket as it heads towards apogee.
832 The height, speed and acceleration are shown along with the
833 maximum values for each of them. This allows you to quickly
834 answer the most commonly asked questions you'll hear during
838 The current latitude and longitude reported by the TeleMetrum GPS are
839 also shown. Note that under high acceleration, these values
840 may not get updated as the GPS receiver loses position
841 fix. Once the rocket starts coasting, the receiver should
842 start reporting position again.
845 Finally, the current igniter voltages are reported as in the
846 Launch Pad tab. This can help diagnose deployment failures
847 caused by wiring which comes loose under high acceleration.
851 <title>Descent</title>
853 Once the rocket has reached apogee and (we hope) activated the
854 apogee charge, attention switches to tracking the rocket on
855 the way back to the ground, and for dual-deploy flights,
856 waiting for the main charge to fire.
859 To monitor whether the apogee charge operated correctly, the
860 current descent rate is reported along with the current
861 height. Good descent rates vary based on the choice of recovery
862 components, but generally range from 15-30m/s on drogue and should
863 be below 10m/s when under the main parachute in a dual-deploy flight.
866 For TeleMetrum altimeters, you can locate the rocket in the sky
867 using the elevation and
868 bearing information to figure out where to look. Elevation is
869 in degrees above the horizon. Bearing is reported in degrees
870 relative to true north. Range can help figure out how big the
871 rocket will appear. Note that all of these values are relative
872 to the pad location. If the elevation is near 90°, the rocket
873 is over the pad, not over you.
876 Finally, the igniter voltages are reported in this tab as
877 well, both to monitor the main charge as well as to see what
878 the status of the apogee charge is. Note that some commercial
879 e-matches are designed to retain continuity even after being
880 fired, and will continue to show as green or return from red to
885 <title>Landed</title>
887 Once the rocket is on the ground, attention switches to
888 recovery. While the radio signal is often lost once the
889 rocket is on the ground, the last reported GPS position is
890 generally within a short distance of the actual landing location.
893 The last reported GPS position is reported both by
894 latitude and longitude as well as a bearing and distance from
895 the launch pad. The distance should give you a good idea of
896 whether to walk or hitch a ride. Take the reported
897 latitude and longitude and enter them into your hand-held GPS
898 unit and have that compute a track to the landing location.
901 Both TeleMini and TeleMetrum will continue to transmit RDF
902 tones after landing, allowing you to locate the rocket by
903 following the radio signal if necessary. You may need to get
904 away from the clutter of the flight line, or even get up on
905 a hill (or your neighbor's RV roof) to receive the RDF signal.
908 The maximum height, speed and acceleration reported
909 during the flight are displayed for your admiring observers.
910 The accuracy of these immediate values depends on the quality
911 of your radio link and how many packets were received.
912 Recovering the on-board data after flight will likely yield
913 more precise results.
916 To get more detailed information about the flight, you can
917 click on the 'Graph Flight' button which will bring up a
918 graph window for the current flight.
922 <title>Site Map</title>
924 When the TeleMetrum has a GPS fix, the Site Map tab will map
925 the rocket's position to make it easier for you to locate the
926 rocket, both while it is in the air, and when it has landed. The
927 rocket's state is indicated by color: white for pad, red for
928 boost, pink for fast, yellow for coast, light blue for drogue,
929 dark blue for main, and black for landed.
932 The map's scale is approximately 3m (10ft) per pixel. The map
933 can be dragged using the left mouse button. The map will attempt
934 to keep the rocket roughly centered while data is being received.
937 Images are fetched automatically via the Google Maps Static API,
938 and cached on disk for reuse. If map images cannot be downloaded,
939 the rocket's path will be traced on a dark gray background
943 You can pre-load images for your favorite launch sites
944 before you leave home; check out the 'Preload Maps' section below.
949 <title>Save Flight Data</title>
951 The altimeter records flight data to its internal flash memory.
952 TeleMetrum data is recorded at a much higher rate than the telemetry
953 system can handle, and is not subject to radio drop-outs. As
954 such, it provides a more complete and precise record of the
955 flight. The 'Save Flight Data' button allows you to read the
956 flash memory and write it to disk. As TeleMini has only a barometer, it
957 records data at the same rate as the telemetry signal, but there will be
958 no data lost due to telemetry drop-outs.
961 Clicking on the 'Save Flight Data' button brings up a list of
962 connected TeleMetrum and TeleDongle devices. If you select a
963 TeleMetrum device, the flight data will be downloaded from that
964 device directly. If you select a TeleDongle device, flight data
965 will be downloaded from an altimeter over radio link via the
966 specified TeleDongle. See the chapter on Controlling An Altimeter
967 Over The Radio Link for more information.
970 After the device has been selected, a dialog showing the
971 flight data saved in the device will be shown allowing you to
972 select which flights to download and which to delete. With
973 version 0.9 or newer firmware, you must erase flights in order
974 for the space they consume to be reused by another
975 flight. This prevents accidentally losing flight data
976 if you neglect to download data before flying again. Note that
977 if there is no more space available in the device, then no
978 data will be recorded during the next flight.
981 The file name for each flight log is computed automatically
982 from the recorded flight date, altimeter serial number and
983 flight number information.
987 <title>Replay Flight</title>
989 Select this button and you are prompted to select a flight
990 record file, either a .telem file recording telemetry data or a
991 .eeprom file containing flight data saved from the altimeter
995 Once a flight record is selected, the flight monitor interface
996 is displayed and the flight is re-enacted in real time. Check
997 the Monitor Flight chapter above to learn how this window operates.
1001 <title>Graph Data</title>
1003 Select this button and you are prompted to select a flight
1004 record file, either a .telem file recording telemetry data or a
1005 .eeprom file containing flight data saved from
1009 Once a flight record is selected, a window with two tabs is
1010 opened. The first tab contains a graph with acceleration
1011 (blue), velocity (green) and altitude (red) of the flight,
1012 measured in metric units. The
1013 apogee(yellow) and main(magenta) igniter voltages are also
1014 displayed; high voltages indicate continuity, low voltages
1015 indicate open circuits. The second tab contains some basic
1019 The graph can be zoomed into a particular area by clicking and
1020 dragging down and to the right. Once zoomed, the graph can be
1021 reset by clicking and dragging up and to the left. Holding down
1022 control and clicking and dragging allows the graph to be panned.
1023 The right mouse button causes a pop-up menu to be displayed, giving
1024 you the option save or print the plot.
1027 Note that telemetry files will generally produce poor graphs
1028 due to the lower sampling rate and missed telemetry packets.
1029 Use saved flight data in .eeprom files for graphing where possible.
1033 <title>Export Data</title>
1035 This tool takes the raw data files and makes them available for
1036 external analysis. When you select this button, you are prompted to
1038 data file (either .eeprom or .telem will do, remember that
1039 .eeprom files contain higher resolution and more continuous
1040 data). Next, a second dialog appears which is used to select
1041 where to write the resulting file. It has a selector to choose
1042 between CSV and KML file formats.
1045 <title>Comma Separated Value Format</title>
1047 This is a text file containing the data in a form suitable for
1048 import into a spreadsheet or other external data analysis
1049 tool. The first few lines of the file contain the version and
1050 configuration information from the altimeter, then
1051 there is a single header line which labels all of the
1052 fields. All of these lines start with a '#' character which
1053 many tools can be configured to skip over.
1056 The remaining lines of the file contain the data, with each
1057 field separated by a comma and at least one space. All of
1058 the sensor values are converted to standard units, with the
1059 barometric data reported in both pressure, altitude and
1060 height above pad units.
1064 <title>Keyhole Markup Language (for Google Earth)</title>
1066 This is the format used by Google Earth to provide an overlay
1067 within that application. With this, you can use Google Earth to
1068 see the whole flight path in 3D.
1073 <title>Configure Altimeter</title>
1075 Select this button and then select either a TeleMetrum or
1076 TeleDongle Device from the list provided. Selecting a TeleDongle
1077 device will use the radio link to configure a remote altimeter.
1080 The first few lines of the dialog provide information about the
1081 connected device, including the product name,
1082 software version and hardware serial number. Below that are the
1083 individual configuration entries.
1086 At the bottom of the dialog, there are four buttons:
1091 Save. This writes any changes to the
1092 configuration parameter block in flash memory. If you don't
1093 press this button, any changes you make will be lost.
1098 Reset. This resets the dialog to the most recently saved values,
1099 erasing any changes you have made.
1104 Reboot. This reboots the device. Use this to
1105 switch from idle to pad mode by rebooting once the rocket is
1106 oriented for flight, or to confirm changes you think you saved
1112 Close. This closes the dialog. Any unsaved changes will be
1118 The rest of the dialog contains the parameters to be configured.
1121 <title>Main Deploy Altitude</title>
1123 This sets the altitude (above the recorded pad altitude) at
1124 which the 'main' igniter will fire. The drop-down menu shows
1125 some common values, but you can edit the text directly and
1126 choose whatever you like. If the apogee charge fires below
1127 this altitude, then the main charge will fire two seconds
1128 after the apogee charge fires.
1132 <title>Apogee Delay</title>
1134 When flying redundant electronics, it's often important to
1135 ensure that multiple apogee charges don't fire at precisely
1136 the same time, as that can over pressurize the apogee deployment
1137 bay and cause a structural failure of the air-frame. The Apogee
1138 Delay parameter tells the flight computer to fire the apogee
1139 charge a certain number of seconds after apogee has been
1144 <title>Radio Frequency</title>
1146 This configures which of the configured frequencies to use for both
1147 telemetry and packet command mode. Note that if you set this
1148 value via packet command mode, you will have to reconfigure
1149 the TeleDongle frequency before you will be able to use packet
1154 <title>Radio Calibration</title>
1156 The radios in every Altus Metrum device are calibrated at the
1157 factory to ensure that they transmit and receive on the
1158 specified frequency. If you need to you can adjust the calibration
1159 by changing this value. Do not do this without understanding what
1160 the value means, read the appendix on calibration and/or the source
1161 code for more information. To change a TeleDongle's calibration,
1162 you must reprogram the unit completely.
1166 <title>Callsign</title>
1168 This sets the call sign included in each telemetry packet. Set this
1169 as needed to conform to your local radio regulations.
1173 <title>Maximum Flight Log Size</title>
1175 This sets the space (in kilobytes) allocated for each flight
1176 log. The available space will be divided into chunks of this
1177 size. A smaller value will allow more flights to be stored,
1178 a larger value will record data from longer flights.
1182 <title>Ignite Mode</title>
1184 TeleMetrum and TeleMini provide two igniter channels as they
1185 were originally designed as dual-deploy flight
1186 computers. This configuration parameter allows the two
1187 channels to be used in different configurations.
1192 Dual Deploy. This is the usual mode of operation; the
1193 'apogee' channel is fired at apogee and the 'main'
1194 channel at the height above ground specified by the
1195 'Main Deploy Altitude' during descent.
1200 Redundant Apogee. This fires both channels at
1201 apogee, the 'apogee' channel first followed after a two second
1202 delay by the 'main' channel.
1207 Redundant Main. This fires both channels at the
1208 height above ground specified by the Main Deploy
1209 Altitude setting during descent. The 'apogee'
1210 channel is fired first, followed after a two second
1211 delay by the 'main' channel.
1217 <title>Pad Orientation</title>
1219 Because it includes an accelerometer, TeleMetrum is
1220 sensitive to the orientation of the board. By default, it
1221 expects the antenna end to point forward. This parameter
1222 allows that default to be changed, permitting the board to
1223 be mounted with the antenna pointing aft instead.
1228 Antenna Up. In this mode, the antenna end of the
1229 TeleMetrum board must point forward, in line with the
1230 expected flight path.
1235 Antenna Down. In this mode, the antenna end of the
1236 TeleMetrum board must point aft, in line with the
1237 expected flight path.
1244 <title>Configure AltosUI</title>
1246 This button presents a dialog so that you can configure the AltosUI global settings.
1249 <title>Voice Settings</title>
1251 AltosUI provides voice announcements during flight so that you
1252 can keep your eyes on the sky and still get information about
1253 the current flight status. However, sometimes you don't want
1258 <para>Enable—turns all voice announcements on and off</para>
1262 Test Voice—Plays a short message allowing you to verify
1263 that the audio system is working and the volume settings
1270 <title>Log Directory</title>
1272 AltosUI logs all telemetry data and saves all TeleMetrum flash
1273 data to this directory. This directory is also used as the
1274 staring point when selecting data files for display or export.
1277 Click on the directory name to bring up a directory choosing
1278 dialog, select a new directory and click 'Select Directory' to
1279 change where AltosUI reads and writes data files.
1283 <title>Callsign</title>
1285 This value is transmitted in each command packet sent from
1286 TeleDongle and received from an altimeter. It is not used in
1287 telemetry mode, as the callsign configured in the altimeter board
1288 is included in all telemetry packets. Configure this
1289 with the AltosUI operators call sign as needed to comply with
1290 your local radio regulations.
1294 <title>Font Size</title>
1296 Selects the set of fonts used in the flight monitor
1297 window. Choose between the small, medium and large sets.
1301 <title>Serial Debug</title>
1303 This causes all communication with a connected device to be
1304 dumped to the console from which AltosUI was started. If
1305 you've started it from an icon or menu entry, the output
1306 will simply be discarded. This mode can be useful to debug
1307 various serial communication issues.
1311 <title>Manage Frequencies</title>
1313 This brings up a dialog where you can configure the set of
1314 frequencies shown in the various frequency menus. You can
1315 add as many as you like, or even reconfigure the default
1316 set. Changing this list does not affect the frequency
1317 settings of any devices, it only changes the set of
1318 frequencies shown in the menus.
1323 <title>Flash Image</title>
1325 This reprograms any Altus Metrum device by using a TeleMetrum
1326 or TeleDongle as a programming dongle. Please read the
1327 directions for flashing devices in the Updating Device
1328 Firmware chapter below.
1331 Once you have the programmer and target devices connected,
1332 push the 'Flash Image' button. That will present a dialog box
1333 listing all of the connected devices. Carefully select the
1334 programmer device, not the device to be programmed.
1337 Next, select the image to flash to the device. These are named
1338 with the product name and firmware version. The file selector
1339 will start in the directory containing the firmware included
1340 with the AltosUI package. Navigate to the directory containing
1341 the desired firmware if it isn't there.
1344 Next, a small dialog containing the device serial number and
1345 RF calibration values should appear. If these values are
1346 incorrect (possibly due to a corrupted image in the device),
1347 enter the correct values here.
1350 Finally, a dialog containing a progress bar will follow the
1351 programming process.
1354 When programming is complete, the target device will
1355 reboot. Note that if the target device is connected via USB, you
1356 will have to unplug it and then plug it back in for the USB
1357 connection to reset so that you can communicate with the device
1362 <title>Fire Igniter</title>
1364 This activates the igniter circuits in TeleMetrum to help test
1365 recovery systems deployment. Because this command can operate
1366 over the Packet Command Link, you can prepare the rocket as
1367 for flight and then test the recovery system without needing
1368 to snake wires inside the air-frame.
1371 Selecting the 'Fire Igniter' button brings up the usual device
1372 selection dialog. Pick the desired TeleDongle or TeleMetrum
1373 device. This brings up another window which shows the current
1374 continuity test status for both apogee and main charges.
1377 Next, select the desired igniter to fire. This will enable the
1381 Select the 'Arm' button. This enables the 'Fire' button. The
1382 word 'Arm' is replaced by a countdown timer indicating that
1383 you have 10 seconds to press the 'Fire' button or the system
1384 will deactivate, at which point you start over again at
1385 selecting the desired igniter.
1389 <title>Scan Channels</title>
1391 This listens for telemetry packets on all of the configured
1392 frequencies, displaying information about each device it
1393 receives a packet from. You can select which of the three
1394 telemetry formats should be tried; by default, it only listens
1395 for the standard telemetry packets used in v1.0 and later
1400 <title>Load Maps</title>
1402 Before heading out to a new launch site, you can use this to
1403 load satellite images in case you don't have internet
1404 connectivity at the site. This loads a fairly large area
1405 around the launch site, which should cover any flight you're likely to make.
1408 There's a drop-down menu of launch sites we know about; if
1409 your favorites aren't there, please let us know the lat/lon
1410 and name of the site. The contents of this list are actually
1411 downloaded at run-time, so as new sites are sent in, they'll
1412 get automatically added to this list.
1415 If the launch site isn't in the list, you can manually enter the lat/lon values
1418 Clicking the 'Load Map' button will fetch images from Google
1419 Maps; note that Google limits how many images you can fetch at
1420 once, so if you load more than one launch site, you may get
1421 some gray areas in the map which indicate that Google is tired
1422 of sending data to you. Try again later.
1426 <title>Monitor Idle</title>
1428 This brings up a dialog similar to the Monitor Flight UI,
1429 except it works with the altimeter in "idle" mode by sending
1430 query commands to discover the current state rather than
1431 listening for telemetry packets.
1436 <title>Using Altus Metrum Products</title>
1438 <title>Being Legal</title>
1440 First off, in the US, you need an <ulink url="http://www.altusmetrum.org/Radio/">amateur radio license</ulink> or
1441 other authorization to legally operate the radio transmitters that are part
1446 <title>In the Rocket</title>
1448 In the rocket itself, you just need a <ulink url="http://www.altusmetrum.org/TeleMetrum/">TeleMetrum</ulink> or
1449 <ulink url="http://www.altusmetrum.org/TeleMini/">TeleMini</ulink> board and
1450 a Li-Po rechargeable battery. An 860mAh battery weighs less than a 9V
1451 alkaline battery, and will run a TeleMetrum for hours.
1452 A 110mAh battery weighs less than a triple A battery and will run a TeleMetrum for
1453 a few hours, or a TeleMini for much (much) longer.
1456 By default, we ship the altimeters with a simple wire antenna. If your
1457 electronics bay or the air-frame it resides within is made of carbon fiber,
1458 which is opaque to RF signals, you may choose to have an SMA connector
1459 installed so that you can run a coaxial cable to an antenna mounted
1460 elsewhere in the rocket.
1464 <title>On the Ground</title>
1466 To receive the data stream from the rocket, you need an antenna and short
1467 feed-line connected to one of our <ulink url="http://www.altusmetrum.org/TeleDongle/">TeleDongle</ulink> units. The
1468 TeleDongle in turn plugs directly into the USB port on a notebook
1469 computer. Because TeleDongle looks like a simple serial port, your computer
1470 does not require special device drivers... just plug it in.
1473 The GUI tool, AltosUI, is written in Java and runs across
1474 Linux, Mac OS and Windows. There's also a suite of C tools
1475 for Linux which can perform most of the same tasks.
1478 After the flight, you can use the radio link to extract the more detailed data
1479 logged in either TeleMetrum or TeleMini devices, or you can use a mini USB cable to plug into the
1480 TeleMetrum board directly. Pulling out the data without having to open up
1481 the rocket is pretty cool! A USB cable is also how you charge the Li-Po
1482 battery, so you'll want one of those anyway... the same cable used by lots
1483 of digital cameras and other modern electronic stuff will work fine.
1486 If your TeleMetrum-equipped rocket lands out of sight, you may enjoy having a hand-held GPS
1487 receiver, so that you can put in a way-point for the last reported rocket
1488 position before touch-down. This makes looking for your rocket a lot like
1489 Geo-Caching... just go to the way-point and look around starting from there.
1492 You may also enjoy having a ham radio "HT" that covers the 70cm band... you
1493 can use that with your antenna to direction-find the rocket on the ground
1494 the same way you can use a Walston or Beeline tracker. This can be handy
1495 if the rocket is hiding in sage brush or a tree, or if the last GPS position
1496 doesn't get you close enough because the rocket dropped into a canyon, or
1497 the wind is blowing it across a dry lake bed, or something like that... Keith
1498 and Bdale both currently own and use the Yaesu VX-7R at launches.
1501 So, to recap, on the ground the hardware you'll need includes:
1502 <orderedlist inheritnum='inherit' numeration='arabic'>
1504 an antenna and feed-line
1513 optionally, a hand-held GPS receiver
1516 optionally, an HT or receiver covering 435 MHz
1521 The best hand-held commercial directional antennas we've found for radio
1522 direction finding rockets are from
1523 <ulink url="http://www.arrowantennas.com/" >
1526 The 440-3 and 440-5 are both good choices for finding a
1527 TeleMetrum- or TeleMini- equipped rocket when used with a suitable 70cm HT.
1531 <title>Data Analysis</title>
1533 Our software makes it easy to log the data from each flight, both the
1534 telemetry received during the flight itself, and the more
1535 complete data log recorded in the flash memory on the altimeter
1536 board. Once this data is on your computer, our post-flight tools make it
1537 easy to quickly get to the numbers everyone wants, like apogee altitude,
1538 max acceleration, and max velocity. You can also generate and view a
1539 standard set of plots showing the altitude, acceleration, and
1540 velocity of the rocket during flight. And you can even export a TeleMetrum data file
1541 usable with Google Maps and Google Earth for visualizing the flight path
1542 in two or three dimensions!
1545 Our ultimate goal is to emit a set of files for each flight that can be
1546 published as a web page per flight, or just viewed on your local disk with
1551 <title>Future Plans</title>
1553 In the future, we intend to offer "companion boards" for the rocket that will
1554 plug in to TeleMetrum to collect additional data, provide more pyro channels,
1558 We are also working on the design of a hand-held ground terminal that will
1559 allow monitoring the rocket's status, collecting data during flight, and
1560 logging data after flight without the need for a notebook computer on the
1561 flight line. Particularly since it is so difficult to read most notebook
1562 screens in direct sunlight, we think this will be a great thing to have.
1565 Because all of our work is open, both the hardware designs and the software,
1566 if you have some great idea for an addition to the current Altus Metrum family,
1567 feel free to dive in and help! Or let us know what you'd like to see that
1568 we aren't already working on, and maybe we'll get excited about it too...
1573 <title>Altimeter Installation Recommendations</title>
1575 Building high-power rockets that fly safely is hard enough. Mix
1576 in some sophisticated electronics and a bunch of radio energy
1577 and oftentimes you find few perfect solutions. This chapter
1578 contains some suggestions about how to install Altus Metrum
1579 products into the rocket air-frame, including how to safely and
1580 reliably mix a variety of electronics into the same air-frame.
1583 <title>Mounting the Altimeter</title>
1585 The first consideration is to ensure that the altimeter is
1586 securely fastened to the air-frame. For TeleMetrum, we use
1587 nylon standoffs and nylon screws; they're good to at least 50G
1588 and cannot cause any electrical issues on the board. For
1589 TeleMini, we usually cut small pieces of 1/16" balsa to fit
1590 under the screw holes, and then take 2x56 nylon screws and
1591 screw them through the TeleMini mounting holes, through the
1592 balsa and into the underlying material.
1594 <orderedlist inheritnum='inherit' numeration='arabic'>
1596 Make sure TeleMetrum is aligned precisely along the axis of
1597 acceleration so that the accelerometer can accurately
1598 capture data during the flight.
1601 Watch for any metal touching components on the
1602 board. Shorting out connections on the bottom of the board
1603 can cause the altimeter to fail during flight.
1608 <title>Dealing with the Antenna</title>
1610 The antenna supplied is just a piece of solid, insulated,
1611 wire. If it gets damaged or broken, it can be easily
1612 replaced. It should be kept straight and not cut; bending or
1613 cutting it will change the resonant frequency and/or
1614 impedance, making it a less efficient radiator and thus
1615 reducing the range of the telemetry signal.
1618 Keeping metal away from the antenna will provide better range
1619 and a more even radiation pattern. In most rockets, it's not
1620 entirely possible to isolate the antenna from metal
1621 components; there are often bolts, all-thread and wires from other
1622 electronics to contend with. Just be aware that the more stuff
1623 like this around the antenna, the lower the range.
1626 Make sure the antenna is not inside a tube made or covered
1627 with conducting material. Carbon fiber is the most common
1628 culprit here -- CF is a good conductor and will effectively
1629 shield the antenna, dramatically reducing signal strength and
1630 range. Metallic flake paint is another effective shielding
1631 material which is to be avoided around any antennas.
1634 If the ebay is large enough, it can be convenient to simply
1635 mount the altimeter at one end and stretch the antenna out
1636 inside. Taping the antenna to the sled can keep it straight
1637 under acceleration. If there are metal rods, keep the
1638 antenna as far away as possible.
1641 For a shorter ebay, it's quite practical to have the antenna
1642 run through a bulkhead and into an adjacent bay. Drill a small
1643 hole in the bulkhead, pass the antenna wire through it and
1644 then seal it up with glue or clay. We've also used acrylic
1645 tubing to create a cavity for the antenna wire. This works a
1646 bit better in that the antenna is known to stay straight and
1647 not get folded by recovery components in the bay. Angle the
1648 tubing towards the side wall of the rocket and it ends up
1649 consuming very little space.
1652 If you need to place the antenna at a distance from the
1653 altimeter, you can replace the antenna with an edge-mounted
1654 SMA connector, and then run 50Ω coax from the board to the
1655 antenna. Building a remote antenna is beyond the scope of this
1660 <title>Preserving GPS Reception</title>
1662 The GPS antenna and receiver in TeleMetrum are highly
1663 sensitive and normally have no trouble tracking enough
1664 satellites to provide accurate position information for
1665 recovering the rocket. However, there are many ways to
1666 attenuate the GPS signal.
1667 <orderedlist inheritnum='inherit' numeration='arabic'>
1669 Conductive tubing or coatings. Carbon fiber and metal
1670 tubing, or metallic paint will all dramatically attenuate the
1671 GPS signal. We've never heard of anyone successfully
1672 receiving GPS from inside these materials.
1675 Metal components near the GPS patch antenna. These will
1676 de-tune the patch antenna, changing the resonant frequency
1677 away from the L1 carrier and reduce the effectiveness of the
1678 antenna. You can place as much stuff as you like beneath the
1679 antenna as that's covered with a ground plane. But, keep
1680 wires and metal out from above the patch antenna.
1686 <title>Radio Frequency Interference</title>
1688 Any altimeter will generate RFI; the digital circuits use
1689 high-frequency clocks that spray radio interference across a
1690 wide band. Altus Metrum altimeters generate intentional radio
1691 signals as well, increasing the amount of RF energy around the board.
1694 Rocketry altimeters also use precise sensors measuring air
1695 pressure and acceleration. Tiny changes in voltage can cause
1696 these sensor readings to vary by a huge amount. When the
1697 sensors start mis-reporting data, the altimeter can either
1698 fire the igniters at the wrong time, or not fire them at all.
1701 Voltages are induced when radio frequency energy is
1702 transmitted from one circuit to another. Here are things that
1703 influence the induced voltage and current:
1707 Keep wires from different circuits apart. Moving circuits
1708 further apart will reduce RFI.
1711 Avoid parallel wires from different circuits. The longer two
1712 wires run parallel to one another, the larger the amount of
1713 transferred energy. Cross wires at right angles to reduce
1717 Twist wires from the same circuits. Two wires the same
1718 distance from the transmitter will get the same amount of
1719 induced energy which will then cancel out. Any time you have
1720 a wire pair running together, twist the pair together to
1721 even out distances and reduce RFI. For altimeters, this
1722 includes battery leads, switch hookups and igniter
1726 Avoid resonant lengths. Know what frequencies are present
1727 in the environment and avoid having wire lengths near a
1728 natural resonant length. Altusmetrum products transmit on the
1729 70cm amateur band, so you should avoid lengths that are a
1730 simple ratio of that length; essentially any multiple of 1/4
1731 of the wavelength (17.5cm).
1736 <title>The Barometric Sensor</title>
1738 Altusmetrum altimeters measure altitude with a barometric
1739 sensor, essentially measuring the amount of air above the
1740 rocket to figure out how high it is. A large number of
1741 measurements are taken as the altimeter initializes itself to
1742 figure out the pad altitude. Subsequent measurements are then
1743 used to compute the height above the pad.
1746 To accurately measure atmospheric pressure, the ebay
1747 containing the altimeter must be vented outside the
1748 air-frame. The vent must be placed in a region of linear
1749 airflow, have smooth edges, and away from areas of increasing or
1750 decreasing pressure.
1753 The barometric sensor in the altimeter is quite sensitive to
1754 chemical damage from the products of APCP or BP combustion, so
1755 make sure the ebay is carefully sealed from any compartment
1756 which contains ejection charges or motors.
1760 <title>Ground Testing</title>
1762 The most important aspect of any installation is careful
1763 ground testing. Bringing an air-frame up to the LCO table which
1764 hasn't been ground tested can lead to delays or ejection
1765 charges firing on the pad, or, even worse, a recovery system
1769 Do a 'full systems' test that includes wiring up all igniters
1770 without any BP and turning on all of the electronics in flight
1771 mode. This will catch any mistakes in wiring and any residual
1772 RFI issues that might accidentally fire igniters at the wrong
1773 time. Let the air-frame sit for several minutes, checking for
1774 adequate telemetry signal strength and GPS lock. If any igniters
1775 fire unexpectedly, find and resolve the issue before loading any
1779 Ground test the ejection charges. Prepare the rocket for
1780 flight, loading ejection charges and igniters. Completely
1781 assemble the air-frame and then use the 'Fire Igniters'
1782 interface through a TeleDongle to command each charge to
1783 fire. Make sure the charge is sufficient to robustly separate
1784 the air-frame and deploy the recovery system.
1789 <title>Updating Device Firmware</title>
1791 The big concept to understand is that you have to use a
1792 TeleDongle as a programmer to update a TeleMetrum or TeleMini,
1793 and a TeleMetrum or other TeleDongle to program the TeleDongle
1794 Due to limited memory resources in the cc1111, we don't support
1795 programming directly over USB.
1798 You may wish to begin by ensuring you have current firmware images.
1799 These are distributed as part of the AltOS software bundle that
1800 also includes the AltosUI ground station program. Newer ground
1801 station versions typically work fine with older firmware versions,
1802 so you don't need to update your devices just to try out new
1803 software features. You can always download the most recent
1804 version from <ulink url="http://www.altusmetrum.org/AltOS/"/>.
1807 We recommend updating the altimeter first, before updating TeleDongle.
1810 <title>Updating TeleMetrum Firmware</title>
1811 <orderedlist inheritnum='inherit' numeration='arabic'>
1813 Find the 'programming cable' that you got as part of the starter
1814 kit, that has a red 8-pin MicroMaTch connector on one end and a
1815 red 4-pin MicroMaTch connector on the other end.
1818 Take the 2 screws out of the TeleDongle case to get access
1819 to the circuit board.
1822 Plug the 8-pin end of the programming cable to the
1823 matching connector on the TeleDongle, and the 4-pin end to the
1824 matching connector on the TeleMetrum.
1825 Note that each MicroMaTch connector has an alignment pin that
1826 goes through a hole in the PC board when you have the cable
1830 Attach a battery to the TeleMetrum board.
1833 Plug the TeleDongle into your computer's USB port, and power
1837 Run AltosUI, and select 'Flash Image' from the File menu.
1840 Pick the TeleDongle device from the list, identifying it as the
1844 Select the image you want put on the TeleMetrum, which should have a
1845 name in the form telemetrum-v1.1-1.0.0.ihx. It should be visible
1846 in the default directory, if not you may have to poke around
1847 your system to find it.
1850 Make sure the configuration parameters are reasonable
1851 looking. If the serial number and/or RF configuration
1852 values aren't right, you'll need to change them.
1855 Hit the 'OK' button and the software should proceed to flash
1856 the TeleMetrum with new firmware, showing a progress bar.
1859 Confirm that the TeleMetrum board seems to have updated OK, which you
1860 can do by plugging in to it over USB and using a terminal program
1861 to connect to the board and issue the 'v' command to check
1865 If something goes wrong, give it another try.
1870 <title>Updating TeleMini Firmware</title>
1871 <orderedlist inheritnum='inherit' numeration='arabic'>
1873 You'll need a special 'programming cable' to reprogram the
1874 TeleMini. It's available on the Altus Metrum web store, or
1875 you can make your own using an 8-pin MicroMaTch connector on
1876 one end and a set of four pins on the other.
1879 Take the 2 screws out of the TeleDongle case to get access
1880 to the circuit board.
1883 Plug the 8-pin end of the programming cable to the matching
1884 connector on the TeleDongle, and the 4-pins into the holes
1885 in the TeleMini circuit board. Note that the MicroMaTch
1886 connector has an alignment pin that goes through a hole in
1887 the PC board when you have the cable oriented correctly, and
1888 that pin 1 on the TeleMini board is marked with a square pad
1889 while the other pins have round pads.
1892 Attach a battery to the TeleMini board.
1895 Plug the TeleDongle into your computer's USB port, and power
1899 Run AltosUI, and select 'Flash Image' from the File menu.
1902 Pick the TeleDongle device from the list, identifying it as the
1906 Select the image you want put on the TeleMini, which should have a
1907 name in the form telemini-v1.0-1.0.0.ihx. It should be visible
1908 in the default directory, if not you may have to poke around
1909 your system to find it.
1912 Make sure the configuration parameters are reasonable
1913 looking. If the serial number and/or RF configuration
1914 values aren't right, you'll need to change them.
1917 Hit the 'OK' button and the software should proceed to flash
1918 the TeleMini with new firmware, showing a progress bar.
1921 Confirm that the TeleMini board seems to have updated OK, which you
1922 can do by configuring it over the radio link through the TeleDongle, or
1923 letting it come up in "flight" mode and listening for telemetry.
1926 If something goes wrong, give it another try.
1931 <title>Updating TeleDongle Firmware</title>
1933 Updating TeleDongle's firmware is just like updating TeleMetrum or TeleMini
1934 firmware, but you use either a TeleMetrum or another TeleDongle as the programmer.
1936 <orderedlist inheritnum='inherit' numeration='arabic'>
1938 Find the 'programming cable' that you got as part of the starter
1939 kit, that has a red 8-pin MicroMaTch connector on one end and a
1940 red 4-pin MicroMaTch connector on the other end.
1943 Find the USB cable that you got as part of the starter kit, and
1944 plug the "mini" end in to the mating connector on TeleMetrum or TeleDongle.
1947 Take the 2 screws out of the TeleDongle case to get access
1948 to the circuit board.
1951 Plug the 8-pin end of the programming cable to the
1952 matching connector on the programmer, and the 4-pin end to the
1953 matching connector on the TeleDongle.
1954 Note that each MicroMaTch connector has an alignment pin that
1955 goes through a hole in the PC board when you have the cable
1959 Attach a battery to the TeleMetrum board if you're using one.
1962 Plug both the programmer and the TeleDongle into your computer's USB
1963 ports, and power up the programmer.
1966 Run AltosUI, and select 'Flash Image' from the File menu.
1969 Pick the programmer device from the list, identifying it as the
1973 Select the image you want put on the TeleDongle, which should have a
1974 name in the form teledongle-v0.2-1.0.0.ihx. It should be visible
1975 in the default directory, if not you may have to poke around
1976 your system to find it.
1979 Make sure the configuration parameters are reasonable
1980 looking. If the serial number and/or RF configuration
1981 values aren't right, you'll need to change them. The TeleDongle
1982 serial number is on the "bottom" of the circuit board, and can
1983 usually be read through the translucent blue plastic case without
1984 needing to remove the board from the case.
1987 Hit the 'OK' button and the software should proceed to flash
1988 the TeleDongle with new firmware, showing a progress bar.
1991 Confirm that the TeleDongle board seems to have updated OK, which you
1992 can do by plugging in to it over USB and using a terminal program
1993 to connect to the board and issue the 'v' command to check
1994 the version, etc. Once you're happy, remove the programming cable
1995 and put the cover back on the TeleDongle.
1998 If something goes wrong, give it another try.
2002 Be careful removing the programming cable from the locking 8-pin
2003 connector on TeleMetrum. You'll need a fingernail or perhaps a thin
2004 screwdriver or knife blade to gently pry the locking ears out
2005 slightly to extract the connector. We used a locking connector on
2006 TeleMetrum to help ensure that the cabling to companion boards
2007 used in a rocket don't ever come loose accidentally in flight.
2012 <title>Hardware Specifications</title>
2014 <title>TeleMetrum Specifications</title>
2018 Recording altimeter for model rocketry.
2023 Supports dual deployment (can fire 2 ejection charges).
2028 70cm ham-band transceiver for telemetry down-link.
2033 Barometric pressure sensor good to 45k feet MSL.
2038 1-axis high-g accelerometer for motor characterization, capable of
2039 +/- 50g using default part.
2044 On-board, integrated GPS receiver with 5Hz update rate capability.
2049 On-board 1 megabyte non-volatile memory for flight data storage.
2054 USB interface for battery charging, configuration, and data recovery.
2059 Fully integrated support for Li-Po rechargeable batteries.
2064 Uses Li-Po to fire e-matches, can be modified to support
2065 optional separate pyro battery if needed.
2070 2.75 x 1 inch board designed to fit inside 29mm air-frame coupler tube.
2076 <title>TeleMini Specifications</title>
2080 Recording altimeter for model rocketry.
2085 Supports dual deployment (can fire 2 ejection charges).
2090 70cm ham-band transceiver for telemetry down-link.
2095 Barometric pressure sensor good to 45k feet MSL.
2100 On-board 5 kilobyte non-volatile memory for flight data storage.
2105 RF interface for battery charging, configuration, and data recovery.
2110 Support for Li-Po rechargeable batteries, using an external charger.
2115 Uses Li-Po to fire e-matches, can be modified to support
2116 optional separate pyro battery if needed.
2121 1.5 x .5 inch board designed to fit inside 18mm air-frame coupler tube.
2130 TeleMetrum seems to shut off when disconnected from the
2131 computer. Make sure the battery is adequately charged. Remember the
2132 unit will pull more power than the USB port can deliver before the
2133 GPS enters "locked" mode. The battery charges best when TeleMetrum
2137 It's impossible to stop the TeleDongle when it's in "p" mode, I have
2138 to unplug the USB cable? Make sure you have tried to "escape out" of
2139 this mode. If this doesn't work the reboot procedure for the
2140 TeleDongle *is* to simply unplug it. 'cu' however will retain it's
2141 outgoing buffer IF your "escape out" ('~~') does not work.
2142 At this point using either 'ao-view' (or possibly
2143 'cutemon') instead of 'cu' will 'clear' the issue and allow renewed
2147 The amber LED (on the TeleMetrum) lights up when both
2148 battery and USB are connected. Does this mean it's charging?
2149 Yes, the yellow LED indicates the charging at the 'regular' rate.
2150 If the led is out but the unit is still plugged into a USB port,
2151 then the battery is being charged at a 'trickle' rate.
2154 There are no "dit-dah-dah-dit" sound or lights like the manual mentions?
2155 That's the "pad" mode. Weak batteries might be the problem.
2156 It is also possible that the TeleMetrum is horizontal and the output
2157 is instead a "dit-dit" meaning 'idle'. For TeleMini, it's possible that
2158 it received a command packet which would have left it in "pad" mode.
2161 How do I save flight data?
2162 Live telemetry is written to file(s) whenever AltosUI is connected
2163 to the TeleDongle. The file area defaults to ~/TeleMetrum
2164 but is easily changed using the menus in AltosUI. The files that
2165 are written end in '.telem'. The after-flight
2166 data-dumped files will end in .eeprom and represent continuous data
2167 unlike the .telem files that are subject to losses
2168 along the RF data path.
2169 See the above instructions on what and how to save the eeprom stored
2170 data after physically retrieving your altimeter. Make sure to save
2171 the on-board data after each flight; while the TeleMetrum can store
2172 multiple flights, you never know when you'll lose the altimeter...
2176 <title>Notes for Older Software</title>
2179 Before AltosUI was written, using Altus Metrum devices required
2180 some finesse with the Linux command line. There was a limited
2181 GUI tool, ao-view, which provided functionality similar to the
2182 Monitor Flight window in AltosUI, but everything else was a
2183 fairly 80's experience. This appendix includes documentation for
2184 using that software.
2188 Both TeleMetrum and TeleDongle can be directly communicated
2189 with using USB ports. The first thing you should try after getting
2190 both units plugged into to your computer's USB port(s) is to run
2191 'ao-list' from a terminal-window to see what port-device-name each
2192 device has been assigned by the operating system.
2193 You will need this information to access the devices via their
2194 respective on-board firmware and data using other command line
2195 programs in the AltOS software suite.
2198 TeleMini can be communicated with through a TeleDongle device
2199 over the radio link. When first booted, TeleMini listens for a
2200 TeleDongle device and if it receives a packet, it goes into
2201 'idle' mode. Otherwise, it goes into 'pad' mode and waits to be
2202 launched. The easiest way to get it talking is to start the
2203 communication link on the TeleDongle and the power up the
2207 To access the device's firmware for configuration you need a terminal
2208 program such as you would use to talk to a modem. The software
2209 authors prefer using the program 'cu' which comes from the UUCP package
2210 on most Unix-like systems such as Linux. An example command line for
2211 cu might be 'cu -l /dev/ttyACM0', substituting the correct number
2212 indicated from running the
2213 ao-list program. Another reasonable terminal program for Linux is
2214 'cutecom'. The default 'escape'
2215 character used by CU (i.e. the character you use to
2216 issue commands to cu itself instead of sending the command as input
2217 to the connected device) is a '~'. You will need this for use in
2218 only two different ways during normal operations. First is to exit
2219 the program by sending a '~.' which is called a 'escape-disconnect'
2220 and allows you to close-out from 'cu'. The
2221 second use will be outlined later.
2224 All of the Altus Metrum devices share the concept of a two level
2225 command set in their firmware.
2226 The first layer has several single letter commands. Once
2227 you are using 'cu' (or 'cutecom') sending (typing) a '?'
2228 returns a full list of these
2229 commands. The second level are configuration sub-commands accessed
2230 using the 'c' command, for
2231 instance typing 'c?' will give you this second level of commands
2232 (all of which require the
2233 letter 'c' to access). Please note that most configuration options
2234 are stored only in Flash memory; TeleDongle doesn't provide any storage
2235 for these options and so they'll all be lost when you unplug it.
2238 Try setting these configuration ('c' or second level menu) values. A good
2239 place to start is by setting your call sign. By default, the boards
2240 use 'N0CALL' which is cute, but not exactly legal!
2241 Spend a few minutes getting comfortable with the units, their
2242 firmware, and 'cu' (or possibly 'cutecom').
2243 For instance, try to send
2244 (type) a 'c r 2' and verify the channel change by sending a 'c s'.
2245 Verify you can connect and disconnect from the units while in your
2246 terminal program by sending the escape-disconnect mentioned above.
2249 To set the radio frequency, use the 'c R' command to specify the
2250 radio transceiver configuration parameter. This parameter is computed
2251 using the desired frequency, 'F', the radio calibration parameter, 'C' (showed by the 'c s' command) and
2252 the standard calibration reference frequency, 'S', (normally 434.550MHz):
2256 Round the result to the nearest integer value.
2257 As with all 'c' sub-commands, follow this with a 'c w' to write the
2258 change to the parameter block in the on-board flash on
2259 your altimeter board if you want the change to stay in place across reboots.
2262 To set the apogee delay, use the 'c d' command.
2263 As with all 'c' sub-commands, follow this with a 'c w' to write the
2264 change to the parameter block in the on-board DataFlash chip.
2267 To set the main deployment altitude, use the 'c m' command.
2268 As with all 'c' sub-commands, follow this with a 'c w' to write the
2269 change to the parameter block in the on-board DataFlash chip.
2272 To calibrate the radio frequency, connect the UHF antenna port to a
2273 frequency counter, set the board to 434.550MHz, and use the 'C'
2274 command to generate a CW carrier. Wait for the transmitter temperature
2275 to stabilize and the frequency to settle down.
2276 Then, divide 434.550 MHz by the
2277 measured frequency and multiply by the current radio cal value show
2278 in the 'c s' command. For an unprogrammed board, the default value
2279 is 1186611. Take the resulting integer and program it using the 'c f'
2280 command. Testing with the 'C' command again should show a carrier
2281 within a few tens of Hertz of the intended frequency.
2282 As with all 'c' sub-commands, follow this with a 'c w' to write the
2283 change to the parameter block in the on-board DataFlash chip.
2286 Note that the 'reboot' command, which is very useful on the altimeters,
2287 will likely just cause problems with the dongle. The *correct* way
2288 to reset the dongle is just to unplug and re-plug it.
2291 A fun thing to do at the launch site and something you can do while
2292 learning how to use these units is to play with the radio link access
2293 between an altimeter and the TeleDongle. Be aware that you *must* create
2294 some physical separation between the devices, otherwise the link will
2295 not function due to signal overload in the receivers in each device.
2298 Now might be a good time to take a break and read the rest of this
2299 manual, particularly about the two "modes" that the altimeters
2300 can be placed in. TeleMetrum uses the position of the device when booting
2301 up will determine whether the unit is in "pad" or "idle" mode. TeleMini
2302 enters "idle" mode when it receives a command packet within the first 5 seconds
2303 of being powered up, otherwise it enters "pad" mode.
2306 You can access an altimeter in idle mode from the TeleDongle's USB
2307 connection using the radio link
2308 by issuing a 'p' command to the TeleDongle. Practice connecting and
2309 disconnecting ('~~' while using 'cu') from the altimeter. If
2310 you cannot escape out of the "p" command, (by using a '~~' when in
2311 CU) then it is likely that your kernel has issues. Try a newer version.
2314 Using this radio link allows you to configure the altimeter, test
2315 fire e-matches and igniters from the flight line, check pyro-match
2316 continuity and so forth. You can leave the unit turned on while it
2317 is in 'idle mode' and then place the
2318 rocket vertically on the launch pad, walk away and then issue a
2319 reboot command. The altimeter will reboot and start sending data
2320 having changed to the "pad" mode. If the TeleDongle is not receiving
2321 this data, you can disconnect 'cu' from the TeleDongle using the
2322 procedures mentioned above and THEN connect to the TeleDongle from
2323 inside 'ao-view'. If this doesn't work, disconnect from the
2324 TeleDongle, unplug it, and try again after plugging it back in.
2327 In order to reduce the chance of accidental firing of pyrotechnic
2328 charges, the command to fire a charge is intentionally somewhat
2329 difficult to type, and the built-in help is slightly cryptic to
2330 prevent accidental echoing of characters from the help text back at
2331 the board from firing a charge. The command to fire the apogee
2332 drogue charge is 'i DoIt drogue' and the command to fire the main
2333 charge is 'i DoIt main'.
2336 On TeleMetrum, the GPS will eventually find enough satellites, lock in on them,
2337 and 'ao-view' will both auditorily announce and visually indicate
2339 Now you can launch knowing that you have a good data path and
2340 good satellite lock for flight data and recovery. Remember
2341 you MUST tell ao-view to connect to the TeleDongle explicitly in
2342 order for ao-view to be able to receive data.
2345 The altimeters provide RDF (radio direction finding) tones on
2346 the pad, during descent and after landing. These can be used to
2347 locate the rocket using a directional antenna; the signal
2348 strength providing an indication of the direction from receiver to rocket.
2351 TeleMetrum also provides GPS tracking data, which can further simplify
2352 locating the rocket once it has landed. (The last good GPS data
2353 received before touch-down will be on the data screen of 'ao-view'.)
2356 Once you have recovered the rocket you can download the eeprom
2357 contents using either 'ao-dumplog' (or possibly 'ao-eeprom'), over
2358 either a USB cable or over the radio link using TeleDongle.
2359 And by following the man page for 'ao-postflight' you can create
2360 various data output reports, graphs, and even KML data to see the
2361 flight trajectory in Google-earth. (Moving the viewing angle making
2362 sure to connect the yellow lines while in Google-earth is the proper
2366 As for ao-view.... some things are in the menu but don't do anything
2367 very useful. The developers have stopped working on ao-view to focus
2368 on a new, cross-platform ground station program. So ao-view may or
2369 may not be updated in the future. Mostly you just use
2370 the Log and Device menus. It has a wonderful display of the incoming
2371 flight data and I am sure you will enjoy what it has to say to you
2372 once you enable the voice output!
2376 <title>Calibration</title>
2378 There are only two calibrations required for a TeleMetrum board, and
2379 only one for TeleDongle and TeleMini. All boards are shipped from
2380 the factory pre-calibrated, but the procedures are documented here
2381 in case they are ever needed. Re-calibration is not supported by
2382 AltosUI, you must connect to the board with a serial terminal program
2383 and interact directly with the on-board command interpreter to effect
2387 <title>Radio Frequency</title>
2389 The radio frequency is synthesized from a clock based on the 48 MHz
2390 crystal on the board. The actual frequency of this oscillator
2391 must be measured to generate a calibration constant. While our
2393 bandwidth is wide enough to allow boards to communicate even when
2394 their oscillators are not on exactly the same frequency, performance
2395 is best when they are closely matched.
2396 Radio frequency calibration requires a calibrated frequency counter.
2397 Fortunately, once set, the variation in frequency due to aging and
2398 temperature changes is small enough that re-calibration by customers
2399 should generally not be required.
2402 To calibrate the radio frequency, connect the UHF antenna port to a
2403 frequency counter, set the board to 434.550MHz, and use the 'C'
2404 command in the on-board command interpreter to generate a CW
2405 carrier. For TeleMetrum, this is best done over USB. For TeleMini,
2406 note that the only way to escape the 'C' command is via power cycle
2407 since the board will no longer be listening for commands once it
2408 starts generating a CW carrier.
2411 Wait for the transmitter temperature to stabilize and the frequency
2412 to settle down. Then, divide 434.550 MHz by the
2413 measured frequency and multiply by the current radio cal value show
2414 in the 'c s' command. For an unprogrammed board, the default value
2415 is 1186611. Take the resulting integer and program it using the 'c f'
2416 command. Testing with the 'C' command again should show a carrier
2417 within a few tens of Hertz of the intended frequency.
2418 As with all 'c' sub-commands, follow this with a 'c w' to write the
2419 change to the parameter block in the on-board DataFlash chip.
2422 Note that any time you re-do the radio frequency calibration, the
2423 radio frequency is reset to the default 434.550 Mhz. If you want
2424 to use another frequency, you will have to set that again after
2425 calibration is completed.
2429 <title>TeleMetrum Accelerometer</title>
2431 The TeleMetrum accelerometer we use has its own 5 volt power
2433 the output must be passed through a resistive voltage divider to match
2434 the input of our 3.3 volt ADC. This means that unlike the barometric
2435 sensor, the output of the acceleration sensor is not ratio-metric to
2436 the ADC converter, and calibration is required. Explicitly
2437 calibrating the accelerometers also allows us to load any device
2438 from a Freescale family that includes at least +/- 40g, 50g, 100g,
2439 and 200g parts. Using gravity,
2440 a simple 2-point calibration yields acceptable results capturing both
2441 the different sensitivities and ranges of the different accelerometer
2442 parts and any variation in power supply voltages or resistor values
2443 in the divider network.
2446 To calibrate the acceleration sensor, use the 'c a 0' command. You
2447 will be prompted to orient the board vertically with the UHF antenna
2448 up and press a key, then to orient the board vertically with the
2449 UHF antenna down and press a key. Note that the accuracy of this
2450 calibration depends primarily on how perfectly vertical and still
2451 the board is held during the cal process. As with all 'c'
2452 sub-commands, follow this with a 'c w' to write the
2453 change to the parameter block in the on-board DataFlash chip.
2456 The +1g and -1g calibration points are included in each telemetry
2457 frame and are part of the header stored in onboard flash to be
2458 downloaded after flight. We always store and return raw ADC
2459 samples for each sensor... so nothing is permanently "lost" or
2460 "damaged" if the calibration is poor.
2463 In the unlikely event an accel cal goes badly, it is possible
2464 that TeleMetrum may always come up in 'pad mode' and as such not be
2465 listening to either the USB or radio link. If that happens,
2466 there is a special hook in the firmware to force the board back
2467 in to 'idle mode' so you can re-do the cal. To use this hook, you
2468 just need to ground the SPI clock pin at power-on. This pin is
2469 available as pin 2 on the 8-pin companion connector, and pin 1 is
2470 ground. So either carefully install a fine-gauge wire jumper
2471 between the two pins closest to the index hole end of the 8-pin
2472 connector, or plug in the programming cable to the 8-pin connector
2473 and use a small screwdriver or similar to short the two pins closest
2474 to the index post on the 4-pin end of the programming cable, and
2475 power up the board. It should come up in 'idle mode' (two beeps),
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2483 <xi:include href="release-notes-1.0.1.xsl" xpointer="xpointer(/article/*)"/>
2484 <xi:include href="release-notes-0.9.2.xsl" xpointer="xpointer(/article/*)"/>
2485 <xi:include href="release-notes-0.9.xsl" xpointer="xpointer(/article/*)"/>
2486 <xi:include href="release-notes-0.8.xsl" xpointer="xpointer(/article/*)"/>
2487 <xi:include href="release-notes-0.7.1.xsl" xpointer="xpointer(/article/*)"/>
2491 <!-- LocalWords: Altusmetrum
projects / fw / altos / blob