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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
593 descent, there's plenty of space to store many flights worth
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.
629 <title>Ignite Mode</title>
631 Instead of firing one charge at apogee and another charge at
632 a fixed height above the ground, you can configure the
633 altimeter to fire both at apogee or both during
634 descent. This was added to support an airframe that has two
635 TeleMetrum computers, one in the fin can and one in the
639 Providing the ability to use both igniters for apogee or
640 main allows some level of redundancy without needing two
641 flight computers. In Redundant Apogee or Redundant Main
642 mode, the two charges will be fired two seconds apart.
646 <title>Pad Orientation</title>
648 TeleMetrum measures acceleration along the axis of the
649 board. Which way the board is oriented affects the sign of
650 the acceleration value. Instead of trying to guess which way
651 the board is mounted in the air frame, TeleMetrum must be
652 explicitly configured for either Antenna Up or Antenna
653 Down. The default, Antenna Up, expects the end of the
654 TeleMetrum board connected to the 70cm antenna to be nearest
655 the nose of the rocket, with the end containing the screw
656 terminals nearest the tail.
664 <title>AltosUI</title>
666 The AltosUI program provides a graphical user interface for
667 interacting with the Altus Metrum product family, including
668 TeleMetrum, TeleMini and TeleDongle. AltosUI can monitor telemetry data,
669 configure TeleMetrum, TeleMini and TeleDongle devices and many other
670 tasks. The primary interface window provides a selection of
671 buttons, one for each major activity in the system. This manual
672 is split into chapters, each of which documents one of the tasks
673 provided from the top-level toolbar.
676 <title>Monitor Flight</title>
677 <subtitle>Receive, Record and Display Telemetry Data</subtitle>
679 Selecting this item brings up a dialog box listing all of the
680 connected TeleDongle devices. When you choose one of these,
681 AltosUI will create a window to display telemetry data as
682 received by the selected TeleDongle device.
685 All telemetry data received are automatically recorded in
686 suitable log files. The name of the files includes the current
687 date and rocket serial and flight numbers.
690 The radio frequency being monitored by the TeleDongle device is
691 displayed at the top of the window. You can configure the
692 frequency by clicking on the frequency box and selecting the desired
693 frequency. AltosUI remembers the last frequency selected for each
694 TeleDongle and selects that automatically the next time you use
698 Below the TeleDongle frequency selector, the window contains a few
699 significant pieces of information about the altimeter providing
700 the telemetry data stream:
704 <para>The configured call-sign</para>
707 <para>The device serial number</para>
710 <para>The flight number. Each altimeter remembers how many
716 The rocket flight state. Each flight passes through several
717 states including Pad, Boost, Fast, Coast, Drogue, Main and
723 The Received Signal Strength Indicator value. This lets
724 you know how strong a signal TeleDongle is receiving. The
725 radio inside TeleDongle operates down to about -99dBm;
726 weaker signals may not be receivable. The packet link uses
727 error correction and detection techniques which prevent
728 incorrect data from being reported.
733 Finally, the largest portion of the window contains a set of
734 tabs, each of which contain some information about the rocket.
735 They're arranged in 'flight order' so that as the flight
736 progresses, the selected tab automatically switches to display
737 data relevant to the current state of the flight. You can select
738 other tabs at any time. The final 'table' tab contains all of
739 the telemetry data in one place.
742 <title>Launch Pad</title>
744 The 'Launch Pad' tab shows information used to decide when the
745 rocket is ready for flight. The first elements include red/green
746 indicators, if any of these is red, you'll want to evaluate
747 whether the rocket is ready to launch:
751 Battery Voltage. This indicates whether the Li-Po battery
752 powering the TeleMetrum has sufficient charge to last for
753 the duration of the flight. A value of more than
754 3.7V is required for a 'GO' status.
759 Apogee Igniter Voltage. This indicates whether the apogee
760 igniter has continuity. If the igniter has a low
761 resistance, then the voltage measured here will be close
762 to the Li-Po battery voltage. A value greater than 3.2V is
763 required for a 'GO' status.
768 Main Igniter Voltage. This indicates whether the main
769 igniter has continuity. If the igniter has a low
770 resistance, then the voltage measured here will be close
771 to the Li-Po battery voltage. A value greater than 3.2V is
772 required for a 'GO' status.
777 On-board Data Logging. This indicates whether there is
778 space remaining on-board to store flight data for the
779 upcoming flight. If you've downloaded data, but failed
780 to erase flights, there may not be any space
781 left. TeleMetrum can store multiple flights, depending
782 on the configured maximum flight log size. TeleMini
783 stores only a single flight, so it will need to be
784 downloaded and erased after each flight to capture
785 data. This only affects on-board flight logging; the
786 altimeter will still transmit telemetry and fire
787 ejection charges at the proper times.
792 GPS Locked. For a TeleMetrum device, this indicates whether the GPS receiver is
793 currently able to compute position information. GPS requires
794 at least 4 satellites to compute an accurate position.
799 GPS Ready. For a TeleMetrum device, this indicates whether GPS has reported at least
800 10 consecutive positions without losing lock. This ensures
801 that the GPS receiver has reliable reception from the
807 The Launchpad tab also shows the computed launch pad position
808 and altitude, averaging many reported positions to improve the
814 <title>Ascent</title>
816 This tab is shown during Boost, Fast and Coast
817 phases. The information displayed here helps monitor the
818 rocket as it heads towards apogee.
821 The height, speed and acceleration are shown along with the
822 maximum values for each of them. This allows you to quickly
823 answer the most commonly asked questions you'll hear during
827 The current latitude and longitude reported by the TeleMetrum GPS are
828 also shown. Note that under high acceleration, these values
829 may not get updated as the GPS receiver loses position
830 fix. Once the rocket starts coasting, the receiver should
831 start reporting position again.
834 Finally, the current igniter voltages are reported as in the
835 Launch Pad tab. This can help diagnose deployment failures
836 caused by wiring which comes loose under high acceleration.
840 <title>Descent</title>
842 Once the rocket has reached apogee and (we hope) activated the
843 apogee charge, attention switches to tracking the rocket on
844 the way back to the ground, and for dual-deploy flights,
845 waiting for the main charge to fire.
848 To monitor whether the apogee charge operated correctly, the
849 current descent rate is reported along with the current
850 height. Good descent rates generally range from 15-30m/s.
853 For TeleMetrum altimeters, you can locate the rocket in the sky
854 using the elevation and
855 bearing information to figure out where to look. Elevation is
856 in degrees above the horizon. Bearing is reported in degrees
857 relative to true north. Range can help figure out how big the
858 rocket will appear. Note that all of these values are relative
859 to the pad location. If the elevation is near 90°, the rocket
860 is over the pad, not over you.
863 Finally, the igniter voltages are reported in this tab as
864 well, both to monitor the main charge as well as to see what
865 the status of the apogee charge is.
869 <title>Landed</title>
871 Once the rocket is on the ground, attention switches to
872 recovery. While the radio signal is generally lost once the
873 rocket is on the ground, the last reported GPS position is
874 generally within a short distance of the actual landing location.
877 The last reported GPS position is reported both by
878 latitude and longitude as well as a bearing and distance from
879 the launch pad. The distance should give you a good idea of
880 whether you'll want to walk or hitch a ride. Take the reported
881 latitude and longitude and enter them into your hand-held GPS
882 unit and have that compute a track to the landing location.
885 Both TeleMini and TeleMetrum will continue to transmit RDF
886 tones after landing, allowing you to locate the rocket by
887 following the radio signal. You may need to get away from
888 the clutter of the flight line, or even get up on a hill (or
889 your neighbor's RV) to receive the RDF signal.
892 The maximum height, speed and acceleration reported
893 during the flight are displayed for your admiring observers.
896 To get more detailed information about the flight, you can
897 click on the 'Graph Flight' button which will bring up a
898 graph window for the current flight.
902 <title>Site Map</title>
904 When the TeleMetrum gets a GPS fix, the Site Map tab will map
905 the rocket's position to make it easier for you to locate the
906 rocket, both while it is in the air, and when it has landed. The
907 rocket's state is indicated by color: white for pad, red for
908 boost, pink for fast, yellow for coast, light blue for drogue,
909 dark blue for main, and black for landed.
912 The map's scale is approximately 3m (10ft) per pixel. The map
913 can be dragged using the left mouse button. The map will attempt
914 to keep the rocket roughly centered while data is being received.
917 Images are fetched automatically via the Google Maps Static API,
918 and are cached for reuse. If map images cannot be downloaded,
919 the rocket's path will be traced on a dark gray background
923 You can pre-load images for your favorite launch sites
924 before you leave home; check out the 'Preload Maps' section below.
929 <title>Save Flight Data</title>
931 The altimeter records flight data to its internal flash memory.
932 The TeleMetrum data is recorded at a much higher rate than the telemetry
933 system can handle, and is not subject to radio drop-outs. As
934 such, it provides a more complete and precise record of the
935 flight. The 'Save Flight Data' button allows you to read the
936 flash memory and write it to disk. As TeleMini has only a barometer, it
937 records data at the same rate as the telemetry signal, but there will be
938 no data lost due to telemetry drop-outs.
941 Clicking on the 'Save Flight Data' button brings up a list of
942 connected TeleMetrum and TeleDongle devices. If you select a
943 TeleMetrum device, the flight data will be downloaded from that
944 device directly. If you select a TeleDongle device, flight data
945 will be downloaded from a TeleMetrum or TeleMini device connected via the
946 packet command link to the specified TeleDongle. See the chapter
947 on Packet Command Mode for more information about this.
950 After the device has been selected, a dialog showing the
951 flight data saved in the device will be shown allowing you to
952 select which flights to download and which to delete. With
953 version 0.9 or newer firmware, you must erase flights in order
954 for the space they consume to be reused by another
955 flight. This prevents you from accidentally losing flight data
956 if you neglect to download data before flying again. Note that
957 if there is no more space available in the device, then no
958 data will be recorded for a flight.
961 The file name for each flight log is computed automatically
962 from the recorded flight date, altimeter serial number and
963 flight number information.
967 <title>Replay Flight</title>
969 Select this button and you are prompted to select a flight
970 record file, either a .telem file recording telemetry data or a
971 .eeprom file containing flight data saved from the altimeter
975 Once a flight record is selected, the flight monitor interface
976 is displayed and the flight is re-enacted in real time. Check
977 the Monitor Flight chapter above to learn how this window operates.
981 <title>Graph Data</title>
983 Select this button and you are prompted to select a flight
984 record file, either a .telem file recording telemetry data or a
985 .eeprom file containing flight data saved from
989 Once a flight record is selected, a window with two tabs is
990 opened. The first tab contains a graph with acceleration
991 (blue), velocity (green) and altitude (red) of the flight are
992 plotted and displayed, measured in metric units. The
993 apogee(yellow) and main(magenta) igniter voltages are also
994 displayed; high voltages indicate continuity, low voltages
995 indicate open circuits. The second tab contains some basic
999 The graph can be zoomed into a particular area by clicking and
1000 dragging down and to the right. Once zoomed, the graph can be
1001 reset by clicking and dragging up and to the left. Holding down
1002 control and clicking and dragging allows the graph to be panned.
1003 The right mouse button causes a pop-up menu to be displayed, giving
1004 you the option save or print the plot.
1007 Note that telemetry files will generally produce poor graphs
1008 due to the lower sampling rate and missed telemetry packets.
1009 Use saved flight data for graphing where possible.
1013 <title>Export Data</title>
1015 This tool takes the raw data files and makes them available for
1016 external analysis. When you select this button, you are prompted to select a flight
1017 data file (either .eeprom or .telem will do, remember that
1018 .eeprom files contain higher resolution and more continuous
1019 data). Next, a second dialog appears which is used to select
1020 where to write the resulting file. It has a selector to choose
1021 between CSV and KML file formats.
1024 <title>Comma Separated Value Format</title>
1026 This is a text file containing the data in a form suitable for
1027 import into a spreadsheet or other external data analysis
1028 tool. The first few lines of the file contain the version and
1029 configuration information from the altimeter, then
1030 there is a single header line which labels all of the
1031 fields. All of these lines start with a '#' character which
1032 most tools can be configured to skip over.
1035 The remaining lines of the file contain the data, with each
1036 field separated by a comma and at least one space. All of
1037 the sensor values are converted to standard units, with the
1038 barometric data reported in both pressure, altitude and
1039 height above pad units.
1043 <title>Keyhole Markup Language (for Google Earth)</title>
1045 This is the format used by
1046 Googleearth to provide an overlay within that
1047 application. With this, you can use Googleearth to see the
1048 whole flight path in 3D.
1053 <title>Configure Altimeter</title>
1055 Select this button and then select either a TeleMetrum or
1056 TeleDongle Device from the list provided. Selecting a TeleDongle
1057 device will use Packet Command Mode to configure a remote
1058 altimeter. Learn how to use this in the Packet Command
1062 The first few lines of the dialog provide information about the
1063 connected device, including the product name,
1064 software version and hardware serial number. Below that are the
1065 individual configuration entries.
1068 At the bottom of the dialog, there are four buttons:
1073 Save. This writes any changes to the
1074 configuration parameter block in flash memory. If you don't
1075 press this button, any changes you make will be lost.
1080 Reset. This resets the dialog to the most recently saved values,
1081 erasing any changes you have made.
1086 Reboot. This reboots the device. Use this to
1087 switch from idle to pad mode by rebooting once the rocket is
1088 oriented for flight.
1093 Close. This closes the dialog. Any unsaved changes will be
1099 The rest of the dialog contains the parameters to be configured.
1102 <title>Main Deploy Altitude</title>
1104 This sets the altitude (above the recorded pad altitude) at
1105 which the 'main' igniter will fire. The drop-down menu shows
1106 some common values, but you can edit the text directly and
1107 choose whatever you like. If the apogee charge fires below
1108 this altitude, then the main charge will fire two seconds
1109 after the apogee charge fires.
1113 <title>Apogee Delay</title>
1115 When flying redundant electronics, it's often important to
1116 ensure that multiple apogee charges don't fire at precisely
1117 the same time as that can over pressurize the apogee deployment
1118 bay and cause a structural failure of the air-frame. The Apogee
1119 Delay parameter tells the flight computer to fire the apogee
1120 charge a certain number of seconds after apogee has been
1125 <title>Radio Frequency</title>
1127 This configures which of the configured frequencies to use for both
1128 telemetry and packet command mode. Note that if you set this
1129 value via packet command mode, you will have to reconfigure
1130 the TeleDongle frequency before you will be able to use packet
1135 <title>Radio Calibration</title>
1137 The radios in every Altus Metrum device are calibrated at the
1138 factory to ensure that they transmit and receive on the
1139 specified frequency. You can adjust that
1140 calibration by changing this value. To change the TeleDongle's
1141 calibration, you must reprogram the unit completely.
1145 <title>Callsign</title>
1147 This sets the call sign included in each telemetry packet. Set this
1148 as needed to conform to your local radio regulations.
1152 <title>Maximum Flight Log Size</title>
1154 This sets the space (in kilobytes) allocated for each flight
1155 log. The available space will be divided into chunks of this
1156 size. A smaller value will allow more flights to be stored,
1157 a larger value will record data from longer flights.
1160 During ascent, TeleMetrum records barometer and
1161 accelerometer values 100 times per second, other analog
1162 information (voltages and temperature) 6 times per second
1163 and GPS data once per second. During descent, the non-GPS
1164 data is recorded 1/10th as often. Each barometer +
1165 accelerometer record takes 8 bytes.
1168 The default, 192kB, will store over 200 seconds of data at
1169 the ascent rate, or over 2000 seconds of data at the descent
1170 rate. That's plenty for most flights. This leaves enough
1171 storage for five flights in a 1MB system, or 10 flights in a
1175 The configuration block takes the last available block of
1176 memory, on v1.0 boards that's just 256 bytes. However, the
1177 flash part on the v1.1 boards uses 64kB for each block.
1180 TeleMini has 5kB of on-board storage, which is plenty for a
1181 single flight. Make sure you download and delete the data
1182 before a subsequent flight or it will not log any data.
1186 <title>Ignite Mode</title>
1188 TeleMetrum and TeleMini provide two igniter channels as they
1189 were originally designed as dual-deploy flight
1190 computers. This configuration parameter allows the two
1191 channels to be used in different configurations.
1196 Dual Deploy. This is the usual mode of operation; the
1197 'apogee' channel is fired at apogee and the 'main'
1198 channel at the height above ground specified by the
1199 'Main Deploy Altitude' during descent.
1204 Redundant Apogee. This fires both channels at
1205 apogee, the 'apogee' channel first followed after a two second
1206 delay by the 'main' channel.
1211 Redundant Main. This fires both channels at the
1212 height above ground specified by the Main Deploy
1213 Altitude setting during descent. The 'apogee'
1214 channel is fired first, followed after a two second
1215 delay by the 'main' channel.
1221 <title>Pad Orientation</title>
1223 Because it includes an accelerometer, TeleMetrum is
1224 sensitive to the orientation of the board. By default, it
1225 expects the antenna end to point forward. This parameter
1226 allows that default to be changed, permitting the board to
1227 be mounted with the antenna pointing aft instead.
1232 Antenna Up. In this mode, the antenna end of the
1233 TeleMetrum board must point forward, in line with the
1234 expected flight path.
1239 Antenna Down. In this mode, the antenna end of the
1240 TeleMetrum board must point aft, in line with the
1241 expected flight path.
1248 <title>Configure AltosUI</title>
1250 This button presents a dialog so that you can configure the AltosUI global settings.
1253 <title>Voice Settings</title>
1255 AltosUI provides voice announcements during flight so that you
1256 can keep your eyes on the sky and still get information about
1257 the current flight status. However, sometimes you don't want
1262 <para>Enable—turns all voice announcements on and off</para>
1266 Test Voice—Plays a short message allowing you to verify
1267 that the audio system is working and the volume settings
1274 <title>Log Directory</title>
1276 AltosUI logs all telemetry data and saves all TeleMetrum flash
1277 data to this directory. This directory is also used as the
1278 staring point when selecting data files for display or export.
1281 Click on the directory name to bring up a directory choosing
1282 dialog, select a new directory and click 'Select Directory' to
1283 change where AltosUI reads and writes data files.
1287 <title>Callsign</title>
1289 This value is transmitted in each command packet sent from
1290 TeleDongle and received from an altimeter. It is not used in
1291 telemetry mode, as the callsign configured in the altimeter board
1292 is included in all telemetry packets. Configure this
1293 with the AltosUI operators call sign as needed to comply with
1294 your local radio regulations.
1298 <title>Font Size</title>
1300 Selects the set of fonts used in the flight monitor
1301 window. Choose between the small, medium and large sets.
1305 <title>Serial Debug</title>
1307 This causes all communication with a connected device to be
1308 dumped to the console from which AltosUI was started. If
1309 you've started it from an icon or menu entry, the output
1310 will simply be discarded. This mode can be useful to debug
1311 various serial communication issues.
1315 <title>Manage Frequencies</title>
1317 This brings up a dialog where you can configure the set of
1318 frequencies shown in the various frequency menus. You can
1319 add as many as you like, or even reconfigure the default
1320 set. Changing this list does not affect the frequency
1321 settings of any devices, it only changes the set of
1322 frequencies shown in the menus.
1327 <title>Flash Image</title>
1329 This reprograms any Altus Metrum device by using a TeleMetrum
1330 or TeleDongle as a programming dongle. Please read the
1331 directions for flashing devices in the Updating Device
1332 Firmware chapter below.
1335 Once you have the programmer and target devices connected,
1336 push the 'Flash Image' button. That will present a dialog box
1337 listing all of the connected devices. Carefully select the
1338 programmer device, not the device to be programmed.
1341 Next, select the image to flash to the device. These are named
1342 with the product name and firmware version. The file selector
1343 will start in the directory containing the firmware included
1344 with the AltosUI package. Navigate to the directory containing
1345 the desired firmware if it isn't there.
1348 Next, a small dialog containing the device serial number and
1349 RF calibration values should appear. If these values are
1350 incorrect (possibly due to a corrupted image in the device),
1351 enter the correct values here.
1354 Finally, a dialog containing a progress bar will follow the
1355 programming process.
1358 When programming is complete, the target device will
1359 reboot. Note that if the target device is connected via USB, you
1360 will have to unplug it and then plug it back in for the USB
1361 connection to reset so that you can communicate with the device
1366 <title>Fire Igniter</title>
1368 This activates the igniter circuits in TeleMetrum to help test
1369 recovery systems deployment. Because this command can operate
1370 over the Packet Command Link, you can prepare the rocket as
1371 for flight and then test the recovery system without needing
1372 to snake wires inside the air-frame.
1375 Selecting the 'Fire Igniter' button brings up the usual device
1376 selection dialog. Pick the desired TeleDongle or TeleMetrum
1377 device. This brings up another window which shows the current
1378 continuity test status for both apogee and main charges.
1381 Next, select the desired igniter to fire. This will enable the
1385 Select the 'Arm' button. This enables the 'Fire' button. The
1386 word 'Arm' is replaced by a countdown timer indicating that
1387 you have 10 seconds to press the 'Fire' button or the system
1388 will deactivate, at which point you start over again at
1389 selecting the desired igniter.
1393 <title>Scan Channels</title>
1395 This listens for telemetry packets on all of the configured
1396 frequencies, displaying information about each device it
1397 receives a packet from. You can select which of the three
1398 telemetry formats should be tried; by default, it only listens
1399 for the standard telemetry packets used in v1.0 and later
1404 <title>Load Maps</title>
1406 Before heading out to a new launch site, you can use this to
1407 load satellite images in case you don't have internet
1408 connectivity at the site. This loads a fairly large area
1409 around the launch site, which should cover any flight you're likely to make.
1412 There's a drop-down menu of launch sites we know about; if
1413 your favorites aren't there, please let us know the lat/lon
1414 and name of the site. The contents of this list are actually
1415 downloaded at run-time, so as new sites are sent in, they'll
1416 get automatically added to this list.
1419 If the launch site isn't in the list, you can manually enter the lat/lon values
1422 Clicking the 'Load Map' button will fetch images from Google
1423 Maps; note that Google limits how many images you can fetch at
1424 once, so if you load more than one launch site, you may get
1425 some gray areas in the map which indicate that Google is tired
1426 of sending data to you. Try again later.
1430 <title>Monitor Idle</title>
1432 This brings up a dialog similar to the Monitor Flight UI,
1433 except it works with the altimeter in "idle" mode by sending
1434 query commands to discover the current state rather than
1435 listening for telemetry packets.
1440 <title>Using Altus Metrum Products</title>
1442 <title>Being Legal</title>
1444 First off, in the US, you need an <ulink url="http://www.altusmetrum.org/Radio/">amateur radio license</ulink> or
1445 other authorization to legally operate the radio transmitters that are part
1450 <title>In the Rocket</title>
1452 In the rocket itself, you just need a <ulink url="http://www.altusmetrum.org/TeleMetrum/">TeleMetrum</ulink> or
1453 <ulink url="http://www.altusmetrum.org/TeleMini/">TeleMini</ulink> board and
1454 a Li-Po rechargeable battery. An 860mAh battery weighs less than a 9V
1455 alkaline battery, and will run a TeleMetrum for hours.
1456 A 110mAh battery weighs less than a triple A battery and will run a TeleMetrum for
1457 a few hours, or a TeleMini for much (much) longer.
1460 By default, we ship the altimeters with a simple wire antenna. If your
1461 electronics bay or the air-frame it resides within is made of carbon fiber,
1462 which is opaque to RF signals, you may choose to have an SMA connector
1463 installed so that you can run a coaxial cable to an antenna mounted
1464 elsewhere in the rocket.
1468 <title>On the Ground</title>
1470 To receive the data stream from the rocket, you need an antenna and short
1471 feed-line connected to one of our <ulink url="http://www.altusmetrum.org/TeleDongle/">TeleDongle</ulink> units. The
1472 TeleDongle in turn plugs directly into the USB port on a notebook
1473 computer. Because TeleDongle looks like a simple serial port, your computer
1474 does not require special device drivers... just plug it in.
1477 The GUI tool, AltosUI, is written in Java and runs across
1478 Linux, Mac OS and Windows. There's also a suite of C tools
1479 for Linux which can perform most of the same tasks.
1482 After the flight, you can use the radio link to extract the more detailed data
1483 logged in either TeleMetrum or TeleMini devices, or you can use a mini USB cable to plug into the
1484 TeleMetrum board directly. Pulling out the data without having to open up
1485 the rocket is pretty cool! A USB cable is also how you charge the Li-Po
1486 battery, so you'll want one of those anyway... the same cable used by lots
1487 of digital cameras and other modern electronic stuff will work fine.
1490 If your TeleMetrum-equipped rocket lands out of sight, you may enjoy having a hand-held GPS
1491 receiver, so that you can put in a way-point for the last reported rocket
1492 position before touch-down. This makes looking for your rocket a lot like
1493 Geo-Caching... just go to the way-point and look around starting from there.
1496 You may also enjoy having a ham radio "HT" that covers the 70cm band... you
1497 can use that with your antenna to direction-find the rocket on the ground
1498 the same way you can use a Walston or Beeline tracker. This can be handy
1499 if the rocket is hiding in sage brush or a tree, or if the last GPS position
1500 doesn't get you close enough because the rocket dropped into a canyon, or
1501 the wind is blowing it across a dry lake bed, or something like that... Keith
1502 and Bdale both currently own and use the Yaesu VX-7R at launches.
1505 So, to recap, on the ground the hardware you'll need includes:
1506 <orderedlist inheritnum='inherit' numeration='arabic'>
1508 an antenna and feed-line
1517 optionally, a hand-held GPS receiver
1520 optionally, an HT or receiver covering 435 MHz
1525 The best hand-held commercial directional antennas we've found for radio
1526 direction finding rockets are from
1527 <ulink url="http://www.arrowantennas.com/" >
1530 The 440-3 and 440-5 are both good choices for finding a
1531 TeleMetrum- or TeleMini- equipped rocket when used with a suitable 70cm HT.
1535 <title>Data Analysis</title>
1537 Our software makes it easy to log the data from each flight, both the
1538 telemetry received during the flight itself, and the more
1539 complete data log recorded in the flash memory on the altimeter
1540 board. Once this data is on your computer, our post-flight tools make it
1541 easy to quickly get to the numbers everyone wants, like apogee altitude,
1542 max acceleration, and max velocity. You can also generate and view a
1543 standard set of plots showing the altitude, acceleration, and
1544 velocity of the rocket during flight. And you can even export a TeleMetrum data file
1545 usable with Google Maps and Google Earth for visualizing the flight path
1546 in two or three dimensions!
1549 Our ultimate goal is to emit a set of files for each flight that can be
1550 published as a web page per flight, or just viewed on your local disk with
1555 <title>Future Plans</title>
1557 In the future, we intend to offer "companion boards" for the rocket that will
1558 plug in to TeleMetrum to collect additional data, provide more pyro channels,
1559 and so forth. A reference design for a companion board will be documented
1560 soon, and will be compatible with open source Arduino programming tools.
1563 We are also working on the design of a hand-held ground terminal that will
1564 allow monitoring the rocket's status, collecting data during flight, and
1565 logging data after flight without the need for a notebook computer on the
1566 flight line. Particularly since it is so difficult to read most notebook
1567 screens in direct sunlight, we think this will be a great thing to have.
1570 Because all of our work is open, both the hardware designs and the software,
1571 if you have some great idea for an addition to the current Altus Metrum family,
1572 feel free to dive in and help! Or let us know what you'd like to see that
1573 we aren't already working on, and maybe we'll get excited about it too...
1578 <title>Altimeter Installation Recommendations</title>
1580 Building high-power rockets that fly safely is hard enough. Mix
1581 in some sophisticated electronics and a bunch of radio energy
1582 and oftentimes you find few perfect solutions. This chapter
1583 contains some suggestions about how to install Altus Metrum
1584 products into the rocket air-frame, including how to safely and
1585 reliably mix a variety of electronics into the same air-frame.
1588 <title>Mounting the Altimeter</title>
1590 The first consideration is to ensure that the altimeter is
1591 securely fastened to the air-frame. For TeleMetrum, we use
1592 nylon standoffs and nylon screws; they're good to at least 50G
1593 and cannot cause any electrical issues on the board. For
1594 TeleMini, we usually cut small pieces of 1/16" balsa to fit
1595 under the screw holes, and then take 2x56 nylon screws and
1596 screw them through the TeleMini mounting holes, through the
1597 balsa and into the underlying material.
1599 <orderedlist inheritnum='inherit' numeration='arabic'>
1601 Make sure TeleMetrum is aligned precisely along the axis of
1602 acceleration so that the accelerometer can accurately
1603 capture data during the flight.
1606 Watch for any metal touching components on the
1607 board. Shorting out connections on the bottom of the board
1608 can cause the altimeter to fail during flight.
1613 <title>Dealing with the Antenna</title>
1615 The antenna supplied is just a piece of solid, insulated,
1616 wire. If it gets damaged or broken, it can be easily
1617 replaced. It should be kept straight and not cut; bending or
1618 cutting it will change the resonant frequency and/or
1619 impedance, making it a less efficient radiator and thus
1620 reducing the range of the telemetry signal.
1623 Keeping metal away from the antenna will provide better range
1624 and a more even radiation pattern. In most rockets, it's not
1625 entirely possible to isolate the antenna from metal
1626 components; there are often bolts, all-thread and wires from other
1627 electronics to contend with. Just be aware that the more stuff
1628 like this around the antenna, the lower the range.
1631 Make sure the antenna is not inside a tube made or covered
1632 with conducting material. Carbon fiber is the most common
1633 culprit here -- CF is a good conductor and will effectively
1634 shield the antenna, dramatically reducing signal strength and
1635 range. Metallic flake paint is another effective shielding
1636 material which is to be avoided around any antennas.
1639 If the ebay is large enough, it can be convenient to simply
1640 mount the altimeter at one end and stretch the antenna out
1641 inside. Taping the antenna to the sled can keep it straight
1642 under acceleration. If there are metal rods, keep the
1643 antenna as far away as possible.
1646 For a shorter ebay, it's quite practical to have the antenna
1647 run through a bulkhead and into an adjacent bay. Drill a small
1648 hole in the bulkhead, pass the antenna wire through it and
1649 then seal it up with glue or clay. We've also used acrylic
1650 tubing to create a cavity for the antenna wire. This works a
1651 bit better in that the antenna is known to stay straight and
1652 not get folded by recovery components in the bay. Angle the
1653 tubing towards the side wall of the rocket and it ends up
1654 consuming very little space.
1657 If you need to place the antenna at a distance from the
1658 altimeter, you can replace the antenna with an edge-mounted
1659 SMA connector, and then run 50Ω coax from the board to the
1660 antenna. Building a remote antenna is beyond the scope of this
1665 <title>Preserving GPS Reception</title>
1667 The GPS antenna and receiver in TeleMetrum are highly
1668 sensitive and normally have no trouble tracking enough
1669 satellites to provide accurate position information for
1670 recovering the rocket. However, there are many ways to
1671 attenuate the GPS signal.
1672 <orderedlist inheritnum='inherit' numeration='arabic'>
1674 Conductive tubing or coatings. Carbon fiber and metal
1675 tubing, or metallic paint will all dramatically attenuate the
1676 GPS signal. We've never heard of anyone successfully
1677 receiving GPS from inside these materials.
1680 Metal components near the GPS patch antenna. These will
1681 de-tune the patch antenna, changing the resonant frequency
1682 away from the L1 carrier and reduce the effectiveness of the
1683 antenna. You can place as much stuff as you like beneath the
1684 antenna as that's covered with a ground plane. But, keep
1685 wires and metal out from above the patch antenna.
1691 <title>Radio Frequency Interference</title>
1693 Any altimeter will generate RFI; the digital circuits use
1694 high-frequency clocks that spray radio interference across a
1695 wide band. Altusmetrum altimeters generate intentional radio
1696 signals as well, increasing the amount of RF energy around the board.
1699 Rocketry altimeters also use precise sensors measuring air
1700 pressure and acceleration. Tiny changes in voltage can cause
1701 these sensor readings to vary by a huge amount. When the
1702 sensors start mis-reporting data, the altimeter can either
1703 fire the igniters at the wrong time, or not fire them at all.
1706 Voltages are induced when radio frequency energy is
1707 transmitted from one circuit to another. Here are things that
1708 increase the induced voltage and current:
1712 Keep wires from different circuits apart. Moving circuits
1713 further apart will reduce RFI.
1716 Avoid parallel wires from different circuits. The longer two
1717 wires run parallel to one another, the larger the amount of
1718 transferred energy. Cross wires at right angles to reduce
1722 Twist wires from the same circuits. Two wires the same
1723 distance from the transmitter will get the same amount of
1724 induced energy which will then cancel out. Any time you have
1725 a wire pair running together, twist the pair together to
1726 even out distances and reduce RFI. For altimeters, this
1727 includes battery leads, switch hookups and igniter
1731 Avoid resonant lengths. Know what frequencies are present
1732 in the environment and avoid having wire lengths near a
1733 natural resonant length. Altusmetrum products transmit on the
1734 70cm amateur band, so you should avoid lengths that are a
1735 simple ratio of that length; essentially any multiple of 1/4
1736 of the wavelength (17.5cm).
1741 <title>The Barometric Sensor</title>
1743 Altusmetrum altimeters measure altitude with a barometric
1744 sensor, essentially measuring the amount of air above the
1745 rocket to figure out how high it is. A large number of
1746 measurements are taken as the altimeter initializes itself to
1747 figure out the pad altitude. Subsequent measurements are then
1748 used to compute the height above the pad.
1751 To accurately measure atmospheric pressure, the ebay
1752 containing the altimeter must be vented outside the
1753 air-frame. The vent must be placed in a region of linear
1754 airflow, smooth and not in an area of increasing or decreasing
1758 The barometric sensor in the altimeter is quite sensitive to
1759 chemical damage from the products of APCP or BP combustion, so
1760 make sure the ebay is carefully sealed from any compartment
1761 which contains ejection charges or motors.
1765 <title>Ground Testing</title>
1767 The most important aspect of any installation is careful
1768 ground testing. Bringing an air-frame up to the LCO table which
1769 hasn't been ground tested can lead to delays or ejection
1770 charges firing on the pad, or, even worse, a recovery system
1774 Do a 'full systems' test that includes wiring up all igniters
1775 without any BP and turning on all of the electronics in flight
1776 mode. This will catch any mistakes in wiring and any residual
1777 RFI issues that might accidentally fire igniters at the wrong
1778 time. Let the air-frame sit for several minutes, checking for
1779 adequate telemetry signal strength and GPS lock.
1782 Ground test the ejection charges. Prepare the rocket for
1783 flight, loading ejection charges and igniters. Completely
1784 assemble the air-frame and then use the 'Fire Igniters'
1785 interface through a TeleDongle to command each charge to
1786 fire. Make sure the charge is sufficient to robustly separate
1787 the air-frame and deploy the recovery system.
1792 <title>Updating Device Firmware</title>
1794 The big conceptual thing to realize is that you have to use a
1795 TeleDongle as a programmer to update a TeleMetrum or TeleMini,
1796 and a TeleMetrum or other TeleDongle to program the TeleDongle
1797 Due to limited memory resources in the cc1111, we don't support
1798 programming directly over USB.
1801 You may wish to begin by ensuring you have current firmware images.
1802 These are distributed as part of the AltOS software bundle that
1803 also includes the AltosUI ground station program. Newer ground
1804 station versions typically work fine with older firmware versions,
1805 so you don't need to update your devices just to try out new
1806 software features. You can always download the most recent
1807 version from <ulink url="http://www.altusmetrum.org/AltOS/"/>.
1810 We recommend updating the altimeter first, before updating TeleDongle.
1813 <title>Updating TeleMetrum Firmware</title>
1814 <orderedlist inheritnum='inherit' numeration='arabic'>
1816 Find the 'programming cable' that you got as part of the starter
1817 kit, that has a red 8-pin MicroMaTch connector on one end and a
1818 red 4-pin MicroMaTch connector on the other end.
1821 Take the 2 screws out of the TeleDongle case to get access
1822 to the circuit board.
1825 Plug the 8-pin end of the programming cable to the
1826 matching connector on the TeleDongle, and the 4-pin end to the
1827 matching connector on the TeleMetrum.
1828 Note that each MicroMaTch connector has an alignment pin that
1829 goes through a hole in the PC board when you have the cable
1833 Attach a battery to the TeleMetrum board.
1836 Plug the TeleDongle into your computer's USB port, and power
1840 Run AltosUI, and select 'Flash Image' from the File menu.
1843 Pick the TeleDongle device from the list, identifying it as the
1847 Select the image you want put on the TeleMetrum, which should have a
1848 name in the form telemetrum-v1.1-1.0.0.ihx. It should be visible
1849 in the default directory, if not you may have to poke around
1850 your system to find it.
1853 Make sure the configuration parameters are reasonable
1854 looking. If the serial number and/or RF configuration
1855 values aren't right, you'll need to change them.
1858 Hit the 'OK' button and the software should proceed to flash
1859 the TeleMetrum with new firmware, showing a progress bar.
1862 Confirm that the TeleMetrum board seems to have updated OK, which you
1863 can do by plugging in to it over USB and using a terminal program
1864 to connect to the board and issue the 'v' command to check
1868 If something goes wrong, give it another try.
1873 <title>Updating TeleMini Firmware</title>
1874 <orderedlist inheritnum='inherit' numeration='arabic'>
1876 You'll need a special 'programming cable' to reprogram the
1877 TeleMini. It's available on the Altus Metrum web store, or
1878 you can make your own using an 8-pin MicroMaTch connector on
1879 one end and a set of four pins on the other.
1882 Take the 2 screws out of the TeleDongle case to get access
1883 to the circuit board.
1886 Plug the 8-pin end of the programming cable to the matching
1887 connector on the TeleDongle, and the 4-pins into the holes
1888 in the TeleMini circuit board. Note that the MicroMaTch
1889 connector has an alignment pin that goes through a hole in
1890 the PC board when you have the cable oriented correctly, and
1891 that pin 1 on the TeleMini board is marked with a square pad
1892 while the other pins have round pads.
1895 Attach a battery to the TeleMini board.
1898 Plug the TeleDongle into your computer's USB port, and power
1902 Run AltosUI, and select 'Flash Image' from the File menu.
1905 Pick the TeleDongle device from the list, identifying it as the
1909 Select the image you want put on the TeleMini, which should have a
1910 name in the form telemini-v1.0-1.0.0.ihx. It should be visible
1911 in the default directory, if not you may have to poke around
1912 your system to find it.
1915 Make sure the configuration parameters are reasonable
1916 looking. If the serial number and/or RF configuration
1917 values aren't right, you'll need to change them.
1920 Hit the 'OK' button and the software should proceed to flash
1921 the TeleMini with new firmware, showing a progress bar.
1924 Confirm that the TeleMini board seems to have updated OK, which you
1925 can do by configuring it over the radio link through the TeleDongle, or
1926 letting it come up in "flight" mode and listening for telemetry.
1929 If something goes wrong, give it another try.
1934 <title>Updating TeleDongle Firmware</title>
1936 Updating TeleDongle's firmware is just like updating TeleMetrum or TeleMini
1937 firmware, but you use either a TeleMetrum or another TeleDongle as the programmer.
1939 <orderedlist inheritnum='inherit' numeration='arabic'>
1941 Find the 'programming cable' that you got as part of the starter
1942 kit, that has a red 8-pin MicroMaTch connector on one end and a
1943 red 4-pin MicroMaTch connector on the other end.
1946 Find the USB cable that you got as part of the starter kit, and
1947 plug the "mini" end in to the mating connector on TeleMetrum or TeleDongle.
1950 Take the 2 screws out of the TeleDongle case to get access
1951 to the circuit board.
1954 Plug the 8-pin end of the programming cable to the
1955 matching connector on the programmer, and the 4-pin end to the
1956 matching connector on the TeleDongle.
1957 Note that each MicroMaTch connector has an alignment pin that
1958 goes through a hole in the PC board when you have the cable
1962 Attach a battery to the TeleMetrum board if you're using one.
1965 Plug both the programmer and the TeleDongle into your computer's USB
1966 ports, and power up the programmer.
1969 Run AltosUI, and select 'Flash Image' from the File menu.
1972 Pick the programmer device from the list, identifying it as the
1976 Select the image you want put on the TeleDongle, which should have a
1977 name in the form teledongle-v0.2-1.0.0.ihx. It should be visible
1978 in the default directory, if not you may have to poke around
1979 your system to find it.
1982 Make sure the configuration parameters are reasonable
1983 looking. If the serial number and/or RF configuration
1984 values aren't right, you'll need to change them. The TeleDongle
1985 serial number is on the "bottom" of the circuit board, and can
1986 usually be read through the translucent blue plastic case without
1987 needing to remove the board from the case.
1990 Hit the 'OK' button and the software should proceed to flash
1991 the TeleDongle with new firmware, showing a progress bar.
1994 Confirm that the TeleDongle board seems to have updated OK, which you
1995 can do by plugging in to it over USB and using a terminal program
1996 to connect to the board and issue the 'v' command to check
1997 the version, etc. Once you're happy, remove the programming cable
1998 and put the cover back on the TeleDongle.
2001 If something goes wrong, give it another try.
2005 Be careful removing the programming cable from the locking 8-pin
2006 connector on TeleMetrum. You'll need a fingernail or perhaps a thin
2007 screwdriver or knife blade to gently pry the locking ears out
2008 slightly to extract the connector. We used a locking connector on
2009 TeleMetrum to help ensure that the cabling to companion boards
2010 used in a rocket don't ever come loose accidentally in flight.
2015 <title>Hardware Specifications</title>
2017 <title>TeleMetrum Specifications</title>
2021 Recording altimeter for model rocketry.
2026 Supports dual deployment (can fire 2 ejection charges).
2031 70cm ham-band transceiver for telemetry down-link.
2036 Barometric pressure sensor good to 45k feet MSL.
2041 1-axis high-g accelerometer for motor characterization, capable of
2042 +/- 50g using default part.
2047 On-board, integrated GPS receiver with 5Hz update rate capability.
2052 On-board 1 megabyte non-volatile memory for flight data storage.
2057 USB interface for battery charging, configuration, and data recovery.
2062 Fully integrated support for Li-Po rechargeable batteries.
2067 Uses Li-Po to fire e-matches, can be modified to support
2068 optional separate pyro battery if needed.
2073 2.75 x 1 inch board designed to fit inside 29mm air-frame coupler tube.
2079 <title>TeleMini Specifications</title>
2083 Recording altimeter for model rocketry.
2088 Supports dual deployment (can fire 2 ejection charges).
2093 70cm ham-band transceiver for telemetry down-link.
2098 Barometric pressure sensor good to 45k feet MSL.
2103 On-board 5 kilobyte non-volatile memory for flight data storage.
2108 RF interface for battery charging, configuration, and data recovery.
2113 Support for Li-Po rechargeable batteries, using an external charger.
2118 Uses Li-Po to fire e-matches, can be modified to support
2119 optional separate pyro battery if needed.
2124 1.5 x .5 inch board designed to fit inside 18mm air-frame coupler tube.
2133 TeleMetrum seems to shut off when disconnected from the
2134 computer. Make sure the battery is adequately charged. Remember the
2135 unit will pull more power than the USB port can deliver before the
2136 GPS enters "locked" mode. The battery charges best when TeleMetrum
2140 It's impossible to stop the TeleDongle when it's in "p" mode, I have
2141 to unplug the USB cable? Make sure you have tried to "escape out" of
2142 this mode. If this doesn't work the reboot procedure for the
2143 TeleDongle *is* to simply unplug it. 'cu' however will retain it's
2144 outgoing buffer IF your "escape out" ('~~') does not work.
2145 At this point using either 'ao-view' (or possibly
2146 'cutemon') instead of 'cu' will 'clear' the issue and allow renewed
2150 The amber LED (on the TeleMetrum) lights up when both
2151 battery and USB are connected. Does this mean it's charging?
2152 Yes, the yellow LED indicates the charging at the 'regular' rate.
2153 If the led is out but the unit is still plugged into a USB port,
2154 then the battery is being charged at a 'trickle' rate.
2157 There are no "dit-dah-dah-dit" sound or lights like the manual mentions?
2158 That's the "pad" mode. Weak batteries might be the problem.
2159 It is also possible that the TeleMetrum is horizontal and the output
2160 is instead a "dit-dit" meaning 'idle'. For TeleMini, it's possible that
2161 it received a command packet which would have left it in "pad" mode.
2164 How do I save flight data?
2165 Live telemetry is written to file(s) whenever AltosUI is connected
2166 to the TeleDongle. The file area defaults to ~/TeleMetrum
2167 but is easily changed using the menus in AltosUI. The files that
2168 are written end in '.telem'. The after-flight
2169 data-dumped files will end in .eeprom and represent continuous data
2170 unlike the .telem files that are subject to losses
2171 along the RF data path.
2172 See the above instructions on what and how to save the eeprom stored
2173 data after physically retrieving your altimeter. Make sure to save
2174 the on-board data after each flight; while the TeleMetrum can store
2175 multiple flights, you never know when you'll lose the altimeter...
2179 <title>Notes for Older Software</title>
2182 Before AltosUI was written, using Altus Metrum devices required
2183 some finesse with the Linux command line. There was a limited
2184 GUI tool, ao-view, which provided functionality similar to the
2185 Monitor Flight window in AltosUI, but everything else was a
2186 fairly 80's experience. This appendix includes documentation for
2187 using that software.
2191 Both TeleMetrum and TeleDongle can be directly communicated
2192 with using USB ports. The first thing you should try after getting
2193 both units plugged into to your computer's USB port(s) is to run
2194 'ao-list' from a terminal-window to see what port-device-name each
2195 device has been assigned by the operating system.
2196 You will need this information to access the devices via their
2197 respective on-board firmware and data using other command line
2198 programs in the AltOS software suite.
2201 TeleMini can be communicated with through a TeleDongle device
2202 over the radio link. When first booted, TeleMini listens for a
2203 TeleDongle device and if it receives a packet, it goes into
2204 'idle' mode. Otherwise, it goes into 'pad' mode and waits to be
2205 launched. The easiest way to get it talking is to start the
2206 communication link on the TeleDongle and the power up the
2210 To access the device's firmware for configuration you need a terminal
2211 program such as you would use to talk to a modem. The software
2212 authors prefer using the program 'cu' which comes from the UUCP package
2213 on most Unix-like systems such as Linux. An example command line for
2214 cu might be 'cu -l /dev/ttyACM0', substituting the correct number
2215 indicated from running the
2216 ao-list program. Another reasonable terminal program for Linux is
2217 'cutecom'. The default 'escape'
2218 character used by CU (i.e. the character you use to
2219 issue commands to cu itself instead of sending the command as input
2220 to the connected device) is a '~'. You will need this for use in
2221 only two different ways during normal operations. First is to exit
2222 the program by sending a '~.' which is called a 'escape-disconnect'
2223 and allows you to close-out from 'cu'. The
2224 second use will be outlined later.
2227 All of the Altus Metrum devices share the concept of a two level
2228 command set in their firmware.
2229 The first layer has several single letter commands. Once
2230 you are using 'cu' (or 'cutecom') sending (typing) a '?'
2231 returns a full list of these
2232 commands. The second level are configuration sub-commands accessed
2233 using the 'c' command, for
2234 instance typing 'c?' will give you this second level of commands
2235 (all of which require the
2236 letter 'c' to access). Please note that most configuration options
2237 are stored only in Flash memory; TeleDongle doesn't provide any storage
2238 for these options and so they'll all be lost when you unplug it.
2241 Try setting these configuration ('c' or second level menu) values. A good
2242 place to start is by setting your call sign. By default, the boards
2243 use 'N0CALL' which is cute, but not exactly legal!
2244 Spend a few minutes getting comfortable with the units, their
2245 firmware, and 'cu' (or possibly 'cutecom').
2246 For instance, try to send
2247 (type) a 'c r 2' and verify the channel change by sending a 'c s'.
2248 Verify you can connect and disconnect from the units while in your
2249 terminal program by sending the escape-disconnect mentioned above.
2252 To set the radio frequency, use the 'c R' command to specify the
2253 radio transceiver configuration parameter. This parameter is computed
2254 using the desired frequency, 'F', the radio calibration parameter, 'C' (showed by the 'c s' command) and
2255 the standard calibration reference frequency, 'S', (normally 434.550MHz):
2259 Round the result to the nearest integer value.
2260 As with all 'c' sub-commands, follow this with a 'c w' to write the
2261 change to the parameter block in the on-board flash on
2262 your altimeter board if you want the change to stay in place across reboots.
2265 To set the apogee delay, use the 'c d' command.
2266 As with all 'c' sub-commands, follow this with a 'c w' to write the
2267 change to the parameter block in the on-board DataFlash chip.
2270 To set the main deployment altitude, use the 'c m' command.
2271 As with all 'c' sub-commands, follow this with a 'c w' to write the
2272 change to the parameter block in the on-board DataFlash chip.
2275 To calibrate the radio frequency, connect the UHF antenna port to a
2276 frequency counter, set the board to 434.550MHz, and use the 'C'
2277 command to generate a CW carrier. Wait for the transmitter temperature
2278 to stabilize and the frequency to settle down.
2279 Then, divide 434.550 MHz by the
2280 measured frequency and multiply by the current radio cal value show
2281 in the 'c s' command. For an unprogrammed board, the default value
2282 is 1186611. Take the resulting integer and program it using the 'c f'
2283 command. Testing with the 'C' command again should show a carrier
2284 within a few tens of Hertz of the intended frequency.
2285 As with all 'c' sub-commands, follow this with a 'c w' to write the
2286 change to the parameter block in the on-board DataFlash chip.
2289 Note that the 'reboot' command, which is very useful on the altimeters,
2290 will likely just cause problems with the dongle. The *correct* way
2291 to reset the dongle is just to unplug and re-plug it.
2294 A fun thing to do at the launch site and something you can do while
2295 learning how to use these units is to play with the radio link access
2296 between an altimeter and the TeleDongle. Be aware that you *must* create
2297 some physical separation between the devices, otherwise the link will
2298 not function due to signal overload in the receivers in each device.
2301 Now might be a good time to take a break and read the rest of this
2302 manual, particularly about the two "modes" that the altimeters
2303 can be placed in. TeleMetrum uses the position of the device when booting
2304 up will determine whether the unit is in "pad" or "idle" mode. TeleMini
2305 enters "idle" mode when it receives a command packet within the first 5 seconds
2306 of being powered up, otherwise it enters "pad" mode.
2309 You can access an altimeter in idle mode from the TeleDongle's USB
2310 connection using the radio link
2311 by issuing a 'p' command to the TeleDongle. Practice connecting and
2312 disconnecting ('~~' while using 'cu') from the altimeter. If
2313 you cannot escape out of the "p" command, (by using a '~~' when in
2314 CU) then it is likely that your kernel has issues. Try a newer version.
2317 Using this radio link allows you to configure the altimeter, test
2318 fire e-matches and igniters from the flight line, check pyro-match
2319 continuity and so forth. You can leave the unit turned on while it
2320 is in 'idle mode' and then place the
2321 rocket vertically on the launch pad, walk away and then issue a
2322 reboot command. The altimeter will reboot and start sending data
2323 having changed to the "pad" mode. If the TeleDongle is not receiving
2324 this data, you can disconnect 'cu' from the TeleDongle using the
2325 procedures mentioned above and THEN connect to the TeleDongle from
2326 inside 'ao-view'. If this doesn't work, disconnect from the
2327 TeleDongle, unplug it, and try again after plugging it back in.
2330 In order to reduce the chance of accidental firing of pyrotechnic
2331 charges, the command to fire a charge is intentionally somewhat
2332 difficult to type, and the built-in help is slightly cryptic to
2333 prevent accidental echoing of characters from the help text back at
2334 the board from firing a charge. The command to fire the apogee
2335 drogue charge is 'i DoIt drogue' and the command to fire the main
2336 charge is 'i DoIt main'.
2339 On TeleMetrum, the GPS will eventually find enough satellites, lock in on them,
2340 and 'ao-view' will both auditorily announce and visually indicate
2342 Now you can launch knowing that you have a good data path and
2343 good satellite lock for flight data and recovery. Remember
2344 you MUST tell ao-view to connect to the TeleDongle explicitly in
2345 order for ao-view to be able to receive data.
2348 The altimeters provide RDF (radio direction finding) tones on
2349 the pad, during descent and after landing. These can be used to
2350 locate the rocket using a directional antenna; the signal
2351 strength providing an indication of the direction from receiver to rocket.
2354 TeleMetrum also provides GPS tracking data, which can further simplify
2355 locating the rocket once it has landed. (The last good GPS data
2356 received before touch-down will be on the data screen of 'ao-view'.)
2359 Once you have recovered the rocket you can download the eeprom
2360 contents using either 'ao-dumplog' (or possibly 'ao-eeprom'), over
2361 either a USB cable or over the radio link using TeleDongle.
2362 And by following the man page for 'ao-postflight' you can create
2363 various data output reports, graphs, and even KML data to see the
2364 flight trajectory in Google-earth. (Moving the viewing angle making
2365 sure to connect the yellow lines while in Google-earth is the proper
2369 As for ao-view.... some things are in the menu but don't do anything
2370 very useful. The developers have stopped working on ao-view to focus
2371 on a new, cross-platform ground station program. So ao-view may or
2372 may not be updated in the future. Mostly you just use
2373 the Log and Device menus. It has a wonderful display of the incoming
2374 flight data and I am sure you will enjoy what it has to say to you
2375 once you enable the voice output!
2379 <title>Calibration</title>
2381 There are only two calibrations required for a TeleMetrum board, and
2382 only one for TeleDongle and TeleMini. All boards are shipped from
2383 the factory pre-calibrated, but the procedures are documented here
2384 in case they are ever needed. Re-calibration is not supported by
2385 AltosUI, you must connect to the board with a serial terminal program
2386 and interact directly with the on-board command interpreter to effect
2390 <title>Radio Frequency</title>
2392 The radio frequency is synthesized from a clock based on the 48 MHz
2393 crystal on the board. The actual frequency of this oscillator
2394 must be measured to generate a calibration constant. While our
2396 bandwidth is wide enough to allow boards to communicate even when
2397 their oscillators are not on exactly the same frequency, performance
2398 is best when they are closely matched.
2399 Radio frequency calibration requires a calibrated frequency counter.
2400 Fortunately, once set, the variation in frequency due to aging and
2401 temperature changes is small enough that re-calibration by customers
2402 should generally not be required.
2405 To calibrate the radio frequency, connect the UHF antenna port to a
2406 frequency counter, set the board to 434.550MHz, and use the 'C'
2407 command in the on-board command interpreter to generate a CW
2408 carrier. For TeleMetrum, this is best done over USB. For TeleMini,
2409 note that the only way to escape the 'C' command is via power cycle
2410 since the board will no longer be listening for commands once it
2411 starts generating a CW carrier.
2414 Wait for the transmitter temperature to stabilize and the frequency
2415 to settle down. Then, divide 434.550 MHz by the
2416 measured frequency and multiply by the current radio cal value show
2417 in the 'c s' command. For an unprogrammed board, the default value
2418 is 1186611. Take the resulting integer and program it using the 'c f'
2419 command. Testing with the 'C' command again should show a carrier
2420 within a few tens of Hertz of the intended frequency.
2421 As with all 'c' sub-commands, follow this with a 'c w' to write the
2422 change to the parameter block in the on-board DataFlash chip.
2425 Note that any time you re-do the radio frequency calibration, the
2426 radio frequency is reset to the default 434.550 Mhz. If you want
2427 to use another frequency, you will have to set that again after
2428 calibration is completed.
2432 <title>TeleMetrum Accelerometer</title>
2434 The TeleMetrum accelerometer we use has its own 5 volt power
2436 the output must be passed through a resistive voltage divider to match
2437 the input of our 3.3 volt ADC. This means that unlike the barometric
2438 sensor, the output of the acceleration sensor is not ratio-metric to
2439 the ADC converter, and calibration is required. Explicitly
2440 calibrating the accelerometers also allows us to load any device
2441 from a Freescale family that includes at least +/- 40g, 50g, 100g,
2442 and 200g parts. Using gravity,
2443 a simple 2-point calibration yields acceptable results capturing both
2444 the different sensitivities and ranges of the different accelerometer
2445 parts and any variation in power supply voltages or resistor values
2446 in the divider network.
2449 To calibrate the acceleration sensor, use the 'c a 0' command. You
2450 will be prompted to orient the board vertically with the UHF antenna
2451 up and press a key, then to orient the board vertically with the
2452 UHF antenna down and press a key. Note that the accuracy of this
2453 calibration depends primarily on how perfectly vertical and still
2454 the board is held during the cal process. As with all 'c'
2455 sub-commands, follow this with a 'c w' to write the
2456 change to the parameter block in the on-board DataFlash chip.
2459 The +1g and -1g calibration points are included in each telemetry
2460 frame and are part of the header stored in onboard flash to be
2461 downloaded after flight. We always store and return raw ADC
2462 samples for each sensor... so nothing is permanently "lost" or
2463 "damaged" if the calibration is poor.
2466 In the unlikely event an accel cal goes badly, it is possible
2467 that TeleMetrum may always come up in 'pad mode' and as such not be
2468 listening to either the USB or radio link. If that happens,
2469 there is a special hook in the firmware to force the board back
2470 in to 'idle mode' so you can re-do the cal. To use this hook, you
2471 just need to ground the SPI clock pin at power-on. This pin is
2472 available as pin 2 on the 8-pin companion connector, and pin 1 is
2473 ground. So either carefully install a fine-gauge wire jumper
2474 between the two pins closest to the index hole end of the 8-pin
2475 connector, or plug in the programming cable to the 8-pin connector
2476 and use a small screwdriver or similar to short the two pins closest
2477 to the index post on the 4-pin end of the programming cable, and
2478 power up the board. It should come up in 'idle mode' (two beeps),
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2488 <xi:include href="release-notes-0.9.xsl" xpointer="xpointer(/article/*)"/>
2489 <xi:include href="release-notes-0.8.xsl" xpointer="xpointer(/article/*)"/>
2490 <xi:include href="release-notes-0.7.1.xsl" xpointer="xpointer(/article/*)"/>
2494 <!-- LocalWords: Altusmetrum