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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 Frequencies</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
591 <title>AltosUI</title>
593 The AltosUI program provides a graphical user interface for
594 interacting with the Altus Metrum product family, including
595 TeleMetrum, TeleMini and TeleDongle. AltosUI can monitor telemetry data,
596 configure TeleMetrum, TeleMini and TeleDongle devices and many other
597 tasks. The primary interface window provides a selection of
598 buttons, one for each major activity in the system. This manual
599 is split into chapters, each of which documents one of the tasks
600 provided from the top-level toolbar.
603 <title>Monitor Flight</title>
604 <subtitle>Receive, Record and Display Telemetry Data</subtitle>
606 Selecting this item brings up a dialog box listing all of the
607 connected TeleDongle devices. When you choose one of these,
608 AltosUI will create a window to display telemetry data as
609 received by the selected TeleDongle device.
612 All telemetry data received are automatically recorded in
613 suitable log files. The name of the files includes the current
614 date and rocket serial and flight numbers.
617 The radio frequency being monitored by the TeleDongle device is
618 displayed at the top of the window. You can configure the
619 frequency by clicking on the frequency box and selecting the desired
620 frequency. AltosUI remembers the last frequency selected for each
621 TeleDongle and selects that automatically the next time you use
625 Below the TeleDongle frequency selector, the window contains a few
626 significant pieces of information about the altimeter providing
627 the telemetry data stream:
631 <para>The configured call-sign</para>
634 <para>The device serial number</para>
637 <para>The flight number. Each altimeter remembers how many
643 The rocket flight state. Each flight passes through several
644 states including Pad, Boost, Fast, Coast, Drogue, Main and
650 The Received Signal Strength Indicator value. This lets
651 you know how strong a signal TeleDongle is receiving. The
652 radio inside TeleDongle operates down to about -99dBm;
653 weaker signals may not be receivable. The packet link uses
654 error detection and correction techniques which prevent
655 incorrect data from being reported.
660 Finally, the largest portion of the window contains a set of
661 tabs, each of which contain some information about the rocket.
662 They're arranged in 'flight order' so that as the flight
663 progresses, the selected tab automatically switches to display
664 data relevant to the current state of the flight. You can select
665 other tabs at any time. The final 'table' tab displays all of
666 the raw telemetry values in one place in a spreadsheet-like format.
669 <title>Launch Pad</title>
671 The 'Launch Pad' tab shows information used to decide when the
672 rocket is ready for flight. The first elements include red/green
673 indicators, if any of these is red, you'll want to evaluate
674 whether the rocket is ready to launch:
678 Battery Voltage. This indicates whether the Li-Po battery
679 powering the TeleMetrum has sufficient charge to last for
680 the duration of the flight. A value of more than
681 3.7V is required for a 'GO' status.
686 Apogee Igniter Voltage. This indicates whether the apogee
687 igniter has continuity. If the igniter has a low
688 resistance, then the voltage measured here will be close
689 to the Li-Po battery voltage. A value greater than 3.2V is
690 required for a 'GO' status.
695 Main Igniter Voltage. This indicates whether the main
696 igniter has continuity. If the igniter has a low
697 resistance, then the voltage measured here will be close
698 to the Li-Po battery voltage. A value greater than 3.2V is
699 required for a 'GO' status.
704 On-board Data Logging. This indicates whether there is
705 space remaining on-board to store flight data for the
706 upcoming flight. If you've downloaded data, but failed
707 to erase flights, there may not be any space
708 left. TeleMetrum can store multiple flights, depending
709 on the configured maximum flight log size. TeleMini
710 stores only a single flight, so it will need to be
711 downloaded and erased after each flight to capture
712 data. This only affects on-board flight logging; the
713 altimeter will still transmit telemetry and fire
714 ejection charges at the proper times.
719 GPS Locked. For a TeleMetrum device, this indicates whether the GPS receiver is
720 currently able to compute position information. GPS requires
721 at least 4 satellites to compute an accurate position.
726 GPS Ready. For a TeleMetrum device, this indicates whether GPS has reported at least
727 10 consecutive positions without losing lock. This ensures
728 that the GPS receiver has reliable reception from the
734 The Launchpad tab also shows the computed launch pad position
735 and altitude, averaging many reported positions to improve the
741 <title>Ascent</title>
743 This tab is shown during Boost, Fast and Coast
744 phases. The information displayed here helps monitor the
745 rocket as it heads towards apogee.
748 The height, speed and acceleration are shown along with the
749 maximum values for each of them. This allows you to quickly
750 answer the most commonly asked questions you'll hear during
754 The current latitude and longitude reported by the TeleMetrum GPS are
755 also shown. Note that under high acceleration, these values
756 may not get updated as the GPS receiver loses position
757 fix. Once the rocket starts coasting, the receiver should
758 start reporting position again.
761 Finally, the current igniter voltages are reported as in the
762 Launch Pad tab. This can help diagnose deployment failures
763 caused by wiring which comes loose under high acceleration.
767 <title>Descent</title>
769 Once the rocket has reached apogee and (we hope) activated the
770 apogee charge, attention switches to tracking the rocket on
771 the way back to the ground, and for dual-deploy flights,
772 waiting for the main charge to fire.
775 To monitor whether the apogee charge operated correctly, the
776 current descent rate is reported along with the current
777 height. Good descent rates vary based on the choice of recovery
778 components, but generally range from 15-30m/s on drogue and should
779 be below 10m/s when under the main parachute in a dual-deploy flight.
782 For TeleMetrum altimeters, you can locate the rocket in the sky
783 using the elevation and
784 bearing information to figure out where to look. Elevation is
785 in degrees above the horizon. Bearing is reported in degrees
786 relative to true north. Range can help figure out how big the
787 rocket will appear. Note that all of these values are relative
788 to the pad location. If the elevation is near 90°, the rocket
789 is over the pad, not over you.
792 Finally, the igniter voltages are reported in this tab as
793 well, both to monitor the main charge as well as to see what
794 the status of the apogee charge is. Note that some commercial
795 e-matches are designed to retain continuity even after being
796 fired, and will continue to show as green or return from red to
801 <title>Landed</title>
803 Once the rocket is on the ground, attention switches to
804 recovery. While the radio signal is often lost once the
805 rocket is on the ground, the last reported GPS position is
806 generally within a short distance of the actual landing location.
809 The last reported GPS position is reported both by
810 latitude and longitude as well as a bearing and distance from
811 the launch pad. The distance should give you a good idea of
812 whether to walk or hitch a ride. Take the reported
813 latitude and longitude and enter them into your hand-held GPS
814 unit and have that compute a track to the landing location.
817 Both TeleMini and TeleMetrum will continue to transmit RDF
818 tones after landing, allowing you to locate the rocket by
819 following the radio signal if necessary. You may need to get
820 away from the clutter of the flight line, or even get up on
821 a hill (or your neighbor's RV roof) to receive the RDF signal.
824 The maximum height, speed and acceleration reported
825 during the flight are displayed for your admiring observers.
826 The accuracy of these immediate values depends on the quality
827 of your radio link and how many packets were received.
828 Recovering the on-board data after flight will likely yield
829 more precise results.
832 To get more detailed information about the flight, you can
833 click on the 'Graph Flight' button which will bring up a
834 graph window for the current flight.
838 <title>Site Map</title>
840 When the TeleMetrum has a GPS fix, the Site Map tab will map
841 the rocket's position to make it easier for you to locate the
842 rocket, both while it is in the air, and when it has landed. The
843 rocket's state is indicated by color: white for pad, red for
844 boost, pink for fast, yellow for coast, light blue for drogue,
845 dark blue for main, and black for landed.
848 The map's scale is approximately 3m (10ft) per pixel. The map
849 can be dragged using the left mouse button. The map will attempt
850 to keep the rocket roughly centered while data is being received.
853 Images are fetched automatically via the Google Maps Static API,
854 and cached on disk for reuse. If map images cannot be downloaded,
855 the rocket's path will be traced on a dark gray background
859 You can pre-load images for your favorite launch sites
860 before you leave home; check out the 'Preload Maps' section below.
865 <title>Save Flight Data</title>
867 The altimeter records flight data to its internal flash memory.
868 TeleMetrum data is recorded at a much higher rate than the telemetry
869 system can handle, and is not subject to radio drop-outs. As
870 such, it provides a more complete and precise record of the
871 flight. The 'Save Flight Data' button allows you to read the
872 flash memory and write it to disk. As TeleMini has only a barometer, it
873 records data at the same rate as the telemetry signal, but there will be
874 no data lost due to telemetry drop-outs.
877 Clicking on the 'Save Flight Data' button brings up a list of
878 connected TeleMetrum and TeleDongle devices. If you select a
879 TeleMetrum device, the flight data will be downloaded from that
880 device directly. If you select a TeleDongle device, flight data
881 will be downloaded from an altimeter over radio link via the
882 specified TeleDongle. See the chapter on Controlling An Altimeter
883 Over The Radio Link for more information.
886 After the device has been selected, a dialog showing the
887 flight data saved in the device will be shown allowing you to
888 select which flights to download and which to delete. With
889 version 0.9 or newer firmware, you must erase flights in order
890 for the space they consume to be reused by another
891 flight. This prevents accidentally losing flight data
892 if you neglect to download data before flying again. Note that
893 if there is no more space available in the device, then no
894 data will be recorded during the next flight.
897 The file name for each flight log is computed automatically
898 from the recorded flight date, altimeter serial number and
899 flight number information.
903 <title>Replay Flight</title>
905 Select this button and you are prompted to select a flight
906 record file, either a .telem file recording telemetry data or a
907 .eeprom file containing flight data saved from the altimeter
911 Once a flight record is selected, the flight monitor interface
912 is displayed and the flight is re-enacted in real time. Check
913 the Monitor Flight chapter above to learn how this window operates.
917 <title>Graph Data</title>
919 Select this button and you are prompted to select a flight
920 record file, either a .telem file recording telemetry data or a
921 .eeprom file containing flight data saved from
925 Once a flight record is selected, a window with two tabs is
926 opened. The first tab contains a graph with acceleration
927 (blue), velocity (green) and altitude (red) of the flight,
928 measured in metric units. The
929 apogee(yellow) and main(magenta) igniter voltages are also
930 displayed; high voltages indicate continuity, low voltages
931 indicate open circuits. The second tab contains some basic
935 The graph can be zoomed into a particular area by clicking and
936 dragging down and to the right. Once zoomed, the graph can be
937 reset by clicking and dragging up and to the left. Holding down
938 control and clicking and dragging allows the graph to be panned.
939 The right mouse button causes a pop-up menu to be displayed, giving
940 you the option save or print the plot.
943 Note that telemetry files will generally produce poor graphs
944 due to the lower sampling rate and missed telemetry packets.
945 Use saved flight data in .eeprom files for graphing where possible.
949 <title>Export Data</title>
951 This tool takes the raw data files and makes them available for
952 external analysis. When you select this button, you are prompted to
954 data file (either .eeprom or .telem will do, remember that
955 .eeprom files contain higher resolution and more continuous
956 data). Next, a second dialog appears which is used to select
957 where to write the resulting file. It has a selector to choose
958 between CSV and KML file formats.
961 <title>Comma Separated Value Format</title>
963 This is a text file containing the data in a form suitable for
964 import into a spreadsheet or other external data analysis
965 tool. The first few lines of the file contain the version and
966 configuration information from the altimeter, then
967 there is a single header line which labels all of the
968 fields. All of these lines start with a '#' character which
969 many tools can be configured to skip over.
972 The remaining lines of the file contain the data, with each
973 field separated by a comma and at least one space. All of
974 the sensor values are converted to standard units, with the
975 barometric data reported in both pressure, altitude and
976 height above pad units.
980 <title>Keyhole Markup Language (for Google Earth)</title>
982 This is the format used by Google Earth to provide an overlay
983 within that application. With this, you can use Google Earth to
984 see the whole flight path in 3D.
989 <title>Configure Altimeter</title>
991 Select this button and then select either a TeleMetrum or
992 TeleDongle Device from the list provided. Selecting a TeleDongle
993 device will use the radio link to configure a remote altimeter.
996 The first few lines of the dialog provide information about the
997 connected device, including the product name,
998 software version and hardware serial number. Below that are the
999 individual configuration entries.
1002 At the bottom of the dialog, there are four buttons:
1007 Save. This writes any changes to the
1008 configuration parameter block in flash memory. If you don't
1009 press this button, any changes you make will be lost.
1014 Reset. This resets the dialog to the most recently saved values,
1015 erasing any changes you have made.
1020 Reboot. This reboots the device. Use this to
1021 switch from idle to pad mode by rebooting once the rocket is
1022 oriented for flight, or to confirm changes you think you saved
1028 Close. This closes the dialog. Any unsaved changes will be
1034 The rest of the dialog contains the parameters to be configured.
1037 <title>Main Deploy Altitude</title>
1039 This sets the altitude (above the recorded pad altitude) at
1040 which the 'main' igniter will fire. The drop-down menu shows
1041 some common values, but you can edit the text directly and
1042 choose whatever you like. If the apogee charge fires below
1043 this altitude, then the main charge will fire two seconds
1044 after the apogee charge fires.
1048 <title>Apogee Delay</title>
1050 When flying redundant electronics, it's often important to
1051 ensure that multiple apogee charges don't fire at precisely
1052 the same time, as that can over pressurize the apogee deployment
1053 bay and cause a structural failure of the air-frame. The Apogee
1054 Delay parameter tells the flight computer to fire the apogee
1055 charge a certain number of seconds after apogee has been
1060 <title>Radio Frequency</title>
1062 This configures which of the configured frequencies to use for both
1063 telemetry and packet command mode. Note that if you set this
1064 value via packet command mode, you will have to reconfigure
1065 the TeleDongle frequency before you will be able to use packet
1070 <title>Radio Calibration</title>
1072 The radios in every Altus Metrum device are calibrated at the
1073 factory to ensure that they transmit and receive on the
1074 specified frequency. If you need to you can adjust the calibration
1075 by changing this value. Do not do this without understanding what
1076 the value means, read the appendix on calibration and/or the source
1077 code for more information. To change a TeleDongle's calibration,
1078 you must reprogram the unit completely.
1082 <title>Callsign</title>
1084 This sets the call sign included in each telemetry packet. Set this
1085 as needed to conform to your local radio regulations.
1089 <title>Maximum Flight Log Size</title>
1091 This sets the space (in kilobytes) allocated for each flight
1092 log. The available space will be divided into chunks of this
1093 size. A smaller value will allow more flights to be stored,
1094 a larger value will record data from longer flights.
1097 During ascent, TeleMetrum records barometer and
1098 accelerometer values 100 times per second, other analog
1099 information (voltages and temperature) 6 times per second
1100 and GPS data once per second. During descent, the non-GPS
1101 data is recorded 1/10th as often. Each barometer +
1102 accelerometer record takes 8 bytes.
1105 The default, 192kB, will store over 200 seconds of data at
1106 the ascent rate, or over 2000 seconds of data at the descent
1107 rate. That's plenty for most flights. This leaves enough
1108 storage for five flights in 1MB systems, or 10 flights in 2MB
1112 The configuration block takes the last available block of
1113 memory, on v1.0 boards that's just 256 bytes. However, the
1114 flash part on the v1.1 boards uses 64kB for each block.
1117 TeleMini has 5kB of on-board storage, which is plenty for a
1118 single flight. Make sure you download and delete the data
1119 before subsequent flights, or TeleMini will not log any data.
1123 <title>Ignite Mode</title>
1125 TeleMetrum and TeleMini provide two igniter channels as they
1126 were originally designed as dual-deploy flight
1127 computers. This configuration parameter allows the two
1128 channels to be used in different configurations.
1133 Dual Deploy. This is the usual mode of operation; the
1134 'apogee' channel is fired at apogee and the 'main'
1135 channel at the height above ground specified by the
1136 'Main Deploy Altitude' during descent.
1141 Redundant Apogee. This fires both channels at
1142 apogee, the 'apogee' channel first followed after a two second
1143 delay by the 'main' channel.
1148 Redundant Main. This fires both channels at the
1149 height above ground specified by the Main Deploy
1150 Altitude setting during descent. The 'apogee'
1151 channel is fired first, followed after a two second
1152 delay by the 'main' channel.
1158 <title>Pad Orientation</title>
1160 Because it includes an accelerometer, TeleMetrum is
1161 sensitive to the orientation of the board. By default, it
1162 expects the antenna end to point forward. This parameter
1163 allows that default to be changed, permitting the board to
1164 be mounted with the antenna pointing aft instead.
1169 Antenna Up. In this mode, the antenna end of the
1170 TeleMetrum board must point forward, in line with the
1171 expected flight path.
1176 Antenna Down. In this mode, the antenna end of the
1177 TeleMetrum board must point aft, in line with the
1178 expected flight path.
1185 <title>Configure AltosUI</title>
1187 This button presents a dialog so that you can configure the AltosUI global settings.
1190 <title>Voice Settings</title>
1192 AltosUI provides voice announcements during flight so that you
1193 can keep your eyes on the sky and still get information about
1194 the current flight status. However, sometimes you don't want
1199 <para>Enable—turns all voice announcements on and off</para>
1203 Test Voice—Plays a short message allowing you to verify
1204 that the audio system is working and the volume settings
1211 <title>Log Directory</title>
1213 AltosUI logs all telemetry data and saves all TeleMetrum flash
1214 data to this directory. This directory is also used as the
1215 staring point when selecting data files for display or export.
1218 Click on the directory name to bring up a directory choosing
1219 dialog, select a new directory and click 'Select Directory' to
1220 change where AltosUI reads and writes data files.
1224 <title>Callsign</title>
1226 This value is transmitted in each command packet sent from
1227 TeleDongle and received from an altimeter. It is not used in
1228 telemetry mode, as the callsign configured in the altimeter board
1229 is included in all telemetry packets. Configure this
1230 with the AltosUI operators call sign as needed to comply with
1231 your local radio regulations.
1235 <title>Font Size</title>
1237 Selects the set of fonts used in the flight monitor
1238 window. Choose between the small, medium and large sets.
1242 <title>Serial Debug</title>
1244 This causes all communication with a connected device to be
1245 dumped to the console from which AltosUI was started. If
1246 you've started it from an icon or menu entry, the output
1247 will simply be discarded. This mode can be useful to debug
1248 various serial communication issues.
1252 <title>Manage Frequencies</title>
1254 This brings up a dialog where you can configure the set of
1255 frequencies shown in the various frequency menus. You can
1256 add as many as you like, or even reconfigure the default
1257 set. Changing this list does not affect the frequency
1258 settings of any devices, it only changes the set of
1259 frequencies shown in the menus.
1264 <title>Flash Image</title>
1266 This reprograms any Altus Metrum device by using a TeleMetrum
1267 or TeleDongle as a programming dongle. Please read the
1268 directions for flashing devices in the Updating Device
1269 Firmware chapter below.
1272 Once you have the programmer and target devices connected,
1273 push the 'Flash Image' button. That will present a dialog box
1274 listing all of the connected devices. Carefully select the
1275 programmer device, not the device to be programmed.
1278 Next, select the image to flash to the device. These are named
1279 with the product name and firmware version. The file selector
1280 will start in the directory containing the firmware included
1281 with the AltosUI package. Navigate to the directory containing
1282 the desired firmware if it isn't there.
1285 Next, a small dialog containing the device serial number and
1286 RF calibration values should appear. If these values are
1287 incorrect (possibly due to a corrupted image in the device),
1288 enter the correct values here.
1291 Finally, a dialog containing a progress bar will follow the
1292 programming process.
1295 When programming is complete, the target device will
1296 reboot. Note that if the target device is connected via USB, you
1297 will have to unplug it and then plug it back in for the USB
1298 connection to reset so that you can communicate with the device
1303 <title>Fire Igniter</title>
1305 This activates the igniter circuits in TeleMetrum to help test
1306 recovery systems deployment. Because this command can operate
1307 over the Packet Command Link, you can prepare the rocket as
1308 for flight and then test the recovery system without needing
1309 to snake wires inside the air-frame.
1312 Selecting the 'Fire Igniter' button brings up the usual device
1313 selection dialog. Pick the desired TeleDongle or TeleMetrum
1314 device. This brings up another window which shows the current
1315 continuity test status for both apogee and main charges.
1318 Next, select the desired igniter to fire. This will enable the
1322 Select the 'Arm' button. This enables the 'Fire' button. The
1323 word 'Arm' is replaced by a countdown timer indicating that
1324 you have 10 seconds to press the 'Fire' button or the system
1325 will deactivate, at which point you start over again at
1326 selecting the desired igniter.
1330 <title>Scan Channels</title>
1332 This listens for telemetry packets on all of the configured
1333 frequencies, displaying information about each device it
1334 receives a packet from. You can select which of the three
1335 telemetry formats should be tried; by default, it only listens
1336 for the standard telemetry packets used in v1.0 and later
1341 <title>Load Maps</title>
1343 Before heading out to a new launch site, you can use this to
1344 load satellite images in case you don't have internet
1345 connectivity at the site. This loads a fairly large area
1346 around the launch site, which should cover any flight you're likely to make.
1349 There's a drop-down menu of launch sites we know about; if
1350 your favorites aren't there, please let us know the lat/lon
1351 and name of the site. The contents of this list are actually
1352 downloaded at run-time, so as new sites are sent in, they'll
1353 get automatically added to this list.
1356 If the launch site isn't in the list, you can manually enter the lat/lon values
1359 Clicking the 'Load Map' button will fetch images from Google
1360 Maps; note that Google limits how many images you can fetch at
1361 once, so if you load more than one launch site, you may get
1362 some gray areas in the map which indicate that Google is tired
1363 of sending data to you. Try again later.
1367 <title>Monitor Idle</title>
1369 This brings up a dialog similar to the Monitor Flight UI,
1370 except it works with the altimeter in "idle" mode by sending
1371 query commands to discover the current state rather than
1372 listening for telemetry packets.
1377 <title>Using Altus Metrum Products</title>
1379 <title>Being Legal</title>
1381 First off, in the US, you need an <ulink url="http://www.altusmetrum.org/Radio/">amateur radio license</ulink> or
1382 other authorization to legally operate the radio transmitters that are part
1387 <title>In the Rocket</title>
1389 In the rocket itself, you just need a <ulink url="http://www.altusmetrum.org/TeleMetrum/">TeleMetrum</ulink> or
1390 <ulink url="http://www.altusmetrum.org/TeleMini/">TeleMini</ulink> board and
1391 a Li-Po rechargeable battery. An 860mAh battery weighs less than a 9V
1392 alkaline battery, and will run a TeleMetrum for hours.
1393 A 110mAh battery weighs less than a triple A battery and will run a TeleMetrum for
1394 a few hours, or a TeleMini for much (much) longer.
1397 By default, we ship the altimeters with a simple wire antenna. If your
1398 electronics bay or the air-frame it resides within is made of carbon fiber,
1399 which is opaque to RF signals, you may choose to have an SMA connector
1400 installed so that you can run a coaxial cable to an antenna mounted
1401 elsewhere in the rocket.
1405 <title>On the Ground</title>
1407 To receive the data stream from the rocket, you need an antenna and short
1408 feed-line connected to one of our <ulink url="http://www.altusmetrum.org/TeleDongle/">TeleDongle</ulink> units. The
1409 TeleDongle in turn plugs directly into the USB port on a notebook
1410 computer. Because TeleDongle looks like a simple serial port, your computer
1411 does not require special device drivers... just plug it in.
1414 The GUI tool, AltosUI, is written in Java and runs across
1415 Linux, Mac OS and Windows. There's also a suite of C tools
1416 for Linux which can perform most of the same tasks.
1419 After the flight, you can use the radio link to extract the more detailed data
1420 logged in either TeleMetrum or TeleMini devices, or you can use a mini USB cable to plug into the
1421 TeleMetrum board directly. Pulling out the data without having to open up
1422 the rocket is pretty cool! A USB cable is also how you charge the Li-Po
1423 battery, so you'll want one of those anyway... the same cable used by lots
1424 of digital cameras and other modern electronic stuff will work fine.
1427 If your TeleMetrum-equipped rocket lands out of sight, you may enjoy having a hand-held GPS
1428 receiver, so that you can put in a way-point for the last reported rocket
1429 position before touch-down. This makes looking for your rocket a lot like
1430 Geo-Caching... just go to the way-point and look around starting from there.
1433 You may also enjoy having a ham radio "HT" that covers the 70cm band... you
1434 can use that with your antenna to direction-find the rocket on the ground
1435 the same way you can use a Walston or Beeline tracker. This can be handy
1436 if the rocket is hiding in sage brush or a tree, or if the last GPS position
1437 doesn't get you close enough because the rocket dropped into a canyon, or
1438 the wind is blowing it across a dry lake bed, or something like that... Keith
1439 and Bdale both currently own and use the Yaesu VX-7R at launches.
1442 So, to recap, on the ground the hardware you'll need includes:
1443 <orderedlist inheritnum='inherit' numeration='arabic'>
1445 an antenna and feed-line
1454 optionally, a hand-held GPS receiver
1457 optionally, an HT or receiver covering 435 MHz
1462 The best hand-held commercial directional antennas we've found for radio
1463 direction finding rockets are from
1464 <ulink url="http://www.arrowantennas.com/" >
1467 The 440-3 and 440-5 are both good choices for finding a
1468 TeleMetrum- or TeleMini- equipped rocket when used with a suitable 70cm HT.
1472 <title>Data Analysis</title>
1474 Our software makes it easy to log the data from each flight, both the
1475 telemetry received during the flight itself, and the more
1476 complete data log recorded in the flash memory on the altimeter
1477 board. Once this data is on your computer, our post-flight tools make it
1478 easy to quickly get to the numbers everyone wants, like apogee altitude,
1479 max acceleration, and max velocity. You can also generate and view a
1480 standard set of plots showing the altitude, acceleration, and
1481 velocity of the rocket during flight. And you can even export a TeleMetrum data file
1482 usable with Google Maps and Google Earth for visualizing the flight path
1483 in two or three dimensions!
1486 Our ultimate goal is to emit a set of files for each flight that can be
1487 published as a web page per flight, or just viewed on your local disk with
1492 <title>Future Plans</title>
1494 In the future, we intend to offer "companion boards" for the rocket that will
1495 plug in to TeleMetrum to collect additional data, provide more pyro channels,
1499 We are also working on the design of a hand-held ground terminal that will
1500 allow monitoring the rocket's status, collecting data during flight, and
1501 logging data after flight without the need for a notebook computer on the
1502 flight line. Particularly since it is so difficult to read most notebook
1503 screens in direct sunlight, we think this will be a great thing to have.
1506 Because all of our work is open, both the hardware designs and the software,
1507 if you have some great idea for an addition to the current Altus Metrum family,
1508 feel free to dive in and help! Or let us know what you'd like to see that
1509 we aren't already working on, and maybe we'll get excited about it too...
1514 <title>Altimeter Installation Recommendations</title>
1516 Building high-power rockets that fly safely is hard enough. Mix
1517 in some sophisticated electronics and a bunch of radio energy
1518 and oftentimes you find few perfect solutions. This chapter
1519 contains some suggestions about how to install Altus Metrum
1520 products into the rocket air-frame, including how to safely and
1521 reliably mix a variety of electronics into the same air-frame.
1524 <title>Mounting the Altimeter</title>
1526 The first consideration is to ensure that the altimeter is
1527 securely fastened to the air-frame. For TeleMetrum, we use
1528 nylon standoffs and nylon screws; they're good to at least 50G
1529 and cannot cause any electrical issues on the board. For
1530 TeleMini, we usually cut small pieces of 1/16" balsa to fit
1531 under the screw holes, and then take 2x56 nylon screws and
1532 screw them through the TeleMini mounting holes, through the
1533 balsa and into the underlying material.
1535 <orderedlist inheritnum='inherit' numeration='arabic'>
1537 Make sure TeleMetrum is aligned precisely along the axis of
1538 acceleration so that the accelerometer can accurately
1539 capture data during the flight.
1542 Watch for any metal touching components on the
1543 board. Shorting out connections on the bottom of the board
1544 can cause the altimeter to fail during flight.
1549 <title>Dealing with the Antenna</title>
1551 The antenna supplied is just a piece of solid, insulated,
1552 wire. If it gets damaged or broken, it can be easily
1553 replaced. It should be kept straight and not cut; bending or
1554 cutting it will change the resonant frequency and/or
1555 impedance, making it a less efficient radiator and thus
1556 reducing the range of the telemetry signal.
1559 Keeping metal away from the antenna will provide better range
1560 and a more even radiation pattern. In most rockets, it's not
1561 entirely possible to isolate the antenna from metal
1562 components; there are often bolts, all-thread and wires from other
1563 electronics to contend with. Just be aware that the more stuff
1564 like this around the antenna, the lower the range.
1567 Make sure the antenna is not inside a tube made or covered
1568 with conducting material. Carbon fiber is the most common
1569 culprit here -- CF is a good conductor and will effectively
1570 shield the antenna, dramatically reducing signal strength and
1571 range. Metallic flake paint is another effective shielding
1572 material which is to be avoided around any antennas.
1575 If the ebay is large enough, it can be convenient to simply
1576 mount the altimeter at one end and stretch the antenna out
1577 inside. Taping the antenna to the sled can keep it straight
1578 under acceleration. If there are metal rods, keep the
1579 antenna as far away as possible.
1582 For a shorter ebay, it's quite practical to have the antenna
1583 run through a bulkhead and into an adjacent bay. Drill a small
1584 hole in the bulkhead, pass the antenna wire through it and
1585 then seal it up with glue or clay. We've also used acrylic
1586 tubing to create a cavity for the antenna wire. This works a
1587 bit better in that the antenna is known to stay straight and
1588 not get folded by recovery components in the bay. Angle the
1589 tubing towards the side wall of the rocket and it ends up
1590 consuming very little space.
1593 If you need to place the antenna at a distance from the
1594 altimeter, you can replace the antenna with an edge-mounted
1595 SMA connector, and then run 50Ω coax from the board to the
1596 antenna. Building a remote antenna is beyond the scope of this
1601 <title>Preserving GPS Reception</title>
1603 The GPS antenna and receiver in TeleMetrum are highly
1604 sensitive and normally have no trouble tracking enough
1605 satellites to provide accurate position information for
1606 recovering the rocket. However, there are many ways to
1607 attenuate the GPS signal.
1608 <orderedlist inheritnum='inherit' numeration='arabic'>
1610 Conductive tubing or coatings. Carbon fiber and metal
1611 tubing, or metallic paint will all dramatically attenuate the
1612 GPS signal. We've never heard of anyone successfully
1613 receiving GPS from inside these materials.
1616 Metal components near the GPS patch antenna. These will
1617 de-tune the patch antenna, changing the resonant frequency
1618 away from the L1 carrier and reduce the effectiveness of the
1619 antenna. You can place as much stuff as you like beneath the
1620 antenna as that's covered with a ground plane. But, keep
1621 wires and metal out from above the patch antenna.
1627 <title>Radio Frequency Interference</title>
1629 Any altimeter will generate RFI; the digital circuits use
1630 high-frequency clocks that spray radio interference across a
1631 wide band. Altus Metrum altimeters generate intentional radio
1632 signals as well, increasing the amount of RF energy around the board.
1635 Rocketry altimeters also use precise sensors measuring air
1636 pressure and acceleration. Tiny changes in voltage can cause
1637 these sensor readings to vary by a huge amount. When the
1638 sensors start mis-reporting data, the altimeter can either
1639 fire the igniters at the wrong time, or not fire them at all.
1642 Voltages are induced when radio frequency energy is
1643 transmitted from one circuit to another. Here are things that
1644 influence the induced voltage and current:
1648 Keep wires from different circuits apart. Moving circuits
1649 further apart will reduce RFI.
1652 Avoid parallel wires from different circuits. The longer two
1653 wires run parallel to one another, the larger the amount of
1654 transferred energy. Cross wires at right angles to reduce
1658 Twist wires from the same circuits. Two wires the same
1659 distance from the transmitter will get the same amount of
1660 induced energy which will then cancel out. Any time you have
1661 a wire pair running together, twist the pair together to
1662 even out distances and reduce RFI. For altimeters, this
1663 includes battery leads, switch hookups and igniter
1667 Avoid resonant lengths. Know what frequencies are present
1668 in the environment and avoid having wire lengths near a
1669 natural resonant length. Altusmetrum products transmit on the
1670 70cm amateur band, so you should avoid lengths that are a
1671 simple ratio of that length; essentially any multiple of 1/4
1672 of the wavelength (17.5cm).
1677 <title>The Barometric Sensor</title>
1679 Altusmetrum altimeters measure altitude with a barometric
1680 sensor, essentially measuring the amount of air above the
1681 rocket to figure out how high it is. A large number of
1682 measurements are taken as the altimeter initializes itself to
1683 figure out the pad altitude. Subsequent measurements are then
1684 used to compute the height above the pad.
1687 To accurately measure atmospheric pressure, the ebay
1688 containing the altimeter must be vented outside the
1689 air-frame. The vent must be placed in a region of linear
1690 airflow, have smooth edges, and away from areas of increasing or
1691 decreasing pressure.
1694 The barometric sensor in the altimeter is quite sensitive to
1695 chemical damage from the products of APCP or BP combustion, so
1696 make sure the ebay is carefully sealed from any compartment
1697 which contains ejection charges or motors.
1701 <title>Ground Testing</title>
1703 The most important aspect of any installation is careful
1704 ground testing. Bringing an air-frame up to the LCO table which
1705 hasn't been ground tested can lead to delays or ejection
1706 charges firing on the pad, or, even worse, a recovery system
1710 Do a 'full systems' test that includes wiring up all igniters
1711 without any BP and turning on all of the electronics in flight
1712 mode. This will catch any mistakes in wiring and any residual
1713 RFI issues that might accidentally fire igniters at the wrong
1714 time. Let the air-frame sit for several minutes, checking for
1715 adequate telemetry signal strength and GPS lock. If any igniters
1716 fire unexpectedly, find and resolve the issue before loading any
1720 Ground test the ejection charges. Prepare the rocket for
1721 flight, loading ejection charges and igniters. Completely
1722 assemble the air-frame and then use the 'Fire Igniters'
1723 interface through a TeleDongle to command each charge to
1724 fire. Make sure the charge is sufficient to robustly separate
1725 the air-frame and deploy the recovery system.
1730 <title>Updating Device Firmware</title>
1732 The big concept to understand is that you have to use a
1733 TeleDongle as a programmer to update a TeleMetrum or TeleMini,
1734 and a TeleMetrum or other TeleDongle to program the TeleDongle
1735 Due to limited memory resources in the cc1111, we don't support
1736 programming directly over USB.
1739 You may wish to begin by ensuring you have current firmware images.
1740 These are distributed as part of the AltOS software bundle that
1741 also includes the AltosUI ground station program. Newer ground
1742 station versions typically work fine with older firmware versions,
1743 so you don't need to update your devices just to try out new
1744 software features. You can always download the most recent
1745 version from <ulink url="http://www.altusmetrum.org/AltOS/"/>.
1748 We recommend updating the altimeter first, before updating TeleDongle.
1751 <title>Updating TeleMetrum Firmware</title>
1752 <orderedlist inheritnum='inherit' numeration='arabic'>
1754 Find the 'programming cable' that you got as part of the starter
1755 kit, that has a red 8-pin MicroMaTch connector on one end and a
1756 red 4-pin MicroMaTch connector on the other end.
1759 Take the 2 screws out of the TeleDongle case to get access
1760 to the circuit board.
1763 Plug the 8-pin end of the programming cable to the
1764 matching connector on the TeleDongle, and the 4-pin end to the
1765 matching connector on the TeleMetrum.
1766 Note that each MicroMaTch connector has an alignment pin that
1767 goes through a hole in the PC board when you have the cable
1771 Attach a battery to the TeleMetrum board.
1774 Plug the TeleDongle into your computer's USB port, and power
1778 Run AltosUI, and select 'Flash Image' from the File menu.
1781 Pick the TeleDongle device from the list, identifying it as the
1785 Select the image you want put on the TeleMetrum, which should have a
1786 name in the form telemetrum-v1.1-1.0.0.ihx. It should be visible
1787 in the default directory, if not you may have to poke around
1788 your system to find it.
1791 Make sure the configuration parameters are reasonable
1792 looking. If the serial number and/or RF configuration
1793 values aren't right, you'll need to change them.
1796 Hit the 'OK' button and the software should proceed to flash
1797 the TeleMetrum with new firmware, showing a progress bar.
1800 Confirm that the TeleMetrum board seems to have updated OK, which you
1801 can do by plugging in to it over USB and using a terminal program
1802 to connect to the board and issue the 'v' command to check
1806 If something goes wrong, give it another try.
1811 <title>Updating TeleMini Firmware</title>
1812 <orderedlist inheritnum='inherit' numeration='arabic'>
1814 You'll need a special 'programming cable' to reprogram the
1815 TeleMini. It's available on the Altus Metrum web store, or
1816 you can make your own using an 8-pin MicroMaTch connector on
1817 one end and a set of four pins on the other.
1820 Take the 2 screws out of the TeleDongle case to get access
1821 to the circuit board.
1824 Plug the 8-pin end of the programming cable to the matching
1825 connector on the TeleDongle, and the 4-pins into the holes
1826 in the TeleMini circuit board. Note that the MicroMaTch
1827 connector has an alignment pin that goes through a hole in
1828 the PC board when you have the cable oriented correctly, and
1829 that pin 1 on the TeleMini board is marked with a square pad
1830 while the other pins have round pads.
1833 Attach a battery to the TeleMini 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 TeleMini, which should have a
1848 name in the form telemini-v1.0-1.0.0.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 TeleMini with new firmware, showing a progress bar.
1862 Confirm that the TeleMini board seems to have updated OK, which you
1863 can do by configuring it over the radio link through the TeleDongle, or
1864 letting it come up in "flight" mode and listening for telemetry.
1867 If something goes wrong, give it another try.
1872 <title>Updating TeleDongle Firmware</title>
1874 Updating TeleDongle's firmware is just like updating TeleMetrum or TeleMini
1875 firmware, but you use either a TeleMetrum or another TeleDongle as the programmer.
1877 <orderedlist inheritnum='inherit' numeration='arabic'>
1879 Find the 'programming cable' that you got as part of the starter
1880 kit, that has a red 8-pin MicroMaTch connector on one end and a
1881 red 4-pin MicroMaTch connector on the other end.
1884 Find the USB cable that you got as part of the starter kit, and
1885 plug the "mini" end in to the mating connector on TeleMetrum or TeleDongle.
1888 Take the 2 screws out of the TeleDongle case to get access
1889 to the circuit board.
1892 Plug the 8-pin end of the programming cable to the
1893 matching connector on the programmer, and the 4-pin end to the
1894 matching connector on the TeleDongle.
1895 Note that each MicroMaTch connector has an alignment pin that
1896 goes through a hole in the PC board when you have the cable
1900 Attach a battery to the TeleMetrum board if you're using one.
1903 Plug both the programmer and the TeleDongle into your computer's USB
1904 ports, and power up the programmer.
1907 Run AltosUI, and select 'Flash Image' from the File menu.
1910 Pick the programmer device from the list, identifying it as the
1914 Select the image you want put on the TeleDongle, which should have a
1915 name in the form teledongle-v0.2-1.0.0.ihx. It should be visible
1916 in the default directory, if not you may have to poke around
1917 your system to find it.
1920 Make sure the configuration parameters are reasonable
1921 looking. If the serial number and/or RF configuration
1922 values aren't right, you'll need to change them. The TeleDongle
1923 serial number is on the "bottom" of the circuit board, and can
1924 usually be read through the translucent blue plastic case without
1925 needing to remove the board from the case.
1928 Hit the 'OK' button and the software should proceed to flash
1929 the TeleDongle with new firmware, showing a progress bar.
1932 Confirm that the TeleDongle board seems to have updated OK, which you
1933 can do by plugging in to it over USB and using a terminal program
1934 to connect to the board and issue the 'v' command to check
1935 the version, etc. Once you're happy, remove the programming cable
1936 and put the cover back on the TeleDongle.
1939 If something goes wrong, give it another try.
1943 Be careful removing the programming cable from the locking 8-pin
1944 connector on TeleMetrum. You'll need a fingernail or perhaps a thin
1945 screwdriver or knife blade to gently pry the locking ears out
1946 slightly to extract the connector. We used a locking connector on
1947 TeleMetrum to help ensure that the cabling to companion boards
1948 used in a rocket don't ever come loose accidentally in flight.
1953 <title>Hardware Specifications</title>
1955 <title>TeleMetrum Specifications</title>
1959 Recording altimeter for model rocketry.
1964 Supports dual deployment (can fire 2 ejection charges).
1969 70cm ham-band transceiver for telemetry down-link.
1974 Barometric pressure sensor good to 45k feet MSL.
1979 1-axis high-g accelerometer for motor characterization, capable of
1980 +/- 50g using default part.
1985 On-board, integrated GPS receiver with 5Hz update rate capability.
1990 On-board 1 megabyte non-volatile memory for flight data storage.
1995 USB interface for battery charging, configuration, and data recovery.
2000 Fully integrated support for Li-Po rechargeable batteries.
2005 Uses Li-Po to fire e-matches, can be modified to support
2006 optional separate pyro battery if needed.
2011 2.75 x 1 inch board designed to fit inside 29mm air-frame coupler tube.
2017 <title>TeleMini 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 On-board 5 kilobyte non-volatile memory for flight data storage.
2046 RF interface for battery charging, configuration, and data recovery.
2051 Support for Li-Po rechargeable batteries, using an external charger.
2056 Uses Li-Po to fire e-matches, can be modified to support
2057 optional separate pyro battery if needed.
2062 1.5 x .5 inch board designed to fit inside 18mm air-frame coupler tube.
2071 TeleMetrum seems to shut off when disconnected from the
2072 computer. Make sure the battery is adequately charged. Remember the
2073 unit will pull more power than the USB port can deliver before the
2074 GPS enters "locked" mode. The battery charges best when TeleMetrum
2078 It's impossible to stop the TeleDongle when it's in "p" mode, I have
2079 to unplug the USB cable? Make sure you have tried to "escape out" of
2080 this mode. If this doesn't work the reboot procedure for the
2081 TeleDongle *is* to simply unplug it. 'cu' however will retain it's
2082 outgoing buffer IF your "escape out" ('~~') does not work.
2083 At this point using either 'ao-view' (or possibly
2084 'cutemon') instead of 'cu' will 'clear' the issue and allow renewed
2088 The amber LED (on the TeleMetrum) lights up when both
2089 battery and USB are connected. Does this mean it's charging?
2090 Yes, the yellow LED indicates the charging at the 'regular' rate.
2091 If the led is out but the unit is still plugged into a USB port,
2092 then the battery is being charged at a 'trickle' rate.
2095 There are no "dit-dah-dah-dit" sound or lights like the manual mentions?
2096 That's the "pad" mode. Weak batteries might be the problem.
2097 It is also possible that the TeleMetrum is horizontal and the output
2098 is instead a "dit-dit" meaning 'idle'. For TeleMini, it's possible that
2099 it received a command packet which would have left it in "pad" mode.
2102 How do I save flight data?
2103 Live telemetry is written to file(s) whenever AltosUI is connected
2104 to the TeleDongle. The file area defaults to ~/TeleMetrum
2105 but is easily changed using the menus in AltosUI. The files that
2106 are written end in '.telem'. The after-flight
2107 data-dumped files will end in .eeprom and represent continuous data
2108 unlike the .telem files that are subject to losses
2109 along the RF data path.
2110 See the above instructions on what and how to save the eeprom stored
2111 data after physically retrieving your altimeter. Make sure to save
2112 the on-board data after each flight; while the TeleMetrum can store
2113 multiple flights, you never know when you'll lose the altimeter...
2117 <title>Notes for Older Software</title>
2120 Before AltosUI was written, using Altus Metrum devices required
2121 some finesse with the Linux command line. There was a limited
2122 GUI tool, ao-view, which provided functionality similar to the
2123 Monitor Flight window in AltosUI, but everything else was a
2124 fairly 80's experience. This appendix includes documentation for
2125 using that software.
2129 Both TeleMetrum and TeleDongle can be directly communicated
2130 with using USB ports. The first thing you should try after getting
2131 both units plugged into to your computer's USB port(s) is to run
2132 'ao-list' from a terminal-window to see what port-device-name each
2133 device has been assigned by the operating system.
2134 You will need this information to access the devices via their
2135 respective on-board firmware and data using other command line
2136 programs in the AltOS software suite.
2139 TeleMini can be communicated with through a TeleDongle device
2140 over the radio link. When first booted, TeleMini listens for a
2141 TeleDongle device and if it receives a packet, it goes into
2142 'idle' mode. Otherwise, it goes into 'pad' mode and waits to be
2143 launched. The easiest way to get it talking is to start the
2144 communication link on the TeleDongle and the power up the
2148 To access the device's firmware for configuration you need a terminal
2149 program such as you would use to talk to a modem. The software
2150 authors prefer using the program 'cu' which comes from the UUCP package
2151 on most Unix-like systems such as Linux. An example command line for
2152 cu might be 'cu -l /dev/ttyACM0', substituting the correct number
2153 indicated from running the
2154 ao-list program. Another reasonable terminal program for Linux is
2155 'cutecom'. The default 'escape'
2156 character used by CU (i.e. the character you use to
2157 issue commands to cu itself instead of sending the command as input
2158 to the connected device) is a '~'. You will need this for use in
2159 only two different ways during normal operations. First is to exit
2160 the program by sending a '~.' which is called a 'escape-disconnect'
2161 and allows you to close-out from 'cu'. The
2162 second use will be outlined later.
2165 All of the Altus Metrum devices share the concept of a two level
2166 command set in their firmware.
2167 The first layer has several single letter commands. Once
2168 you are using 'cu' (or 'cutecom') sending (typing) a '?'
2169 returns a full list of these
2170 commands. The second level are configuration sub-commands accessed
2171 using the 'c' command, for
2172 instance typing 'c?' will give you this second level of commands
2173 (all of which require the
2174 letter 'c' to access). Please note that most configuration options
2175 are stored only in Flash memory; TeleDongle doesn't provide any storage
2176 for these options and so they'll all be lost when you unplug it.
2179 Try setting these configuration ('c' or second level menu) values. A good
2180 place to start is by setting your call sign. By default, the boards
2181 use 'N0CALL' which is cute, but not exactly legal!
2182 Spend a few minutes getting comfortable with the units, their
2183 firmware, and 'cu' (or possibly 'cutecom').
2184 For instance, try to send
2185 (type) a 'c r 2' and verify the channel change by sending a 'c s'.
2186 Verify you can connect and disconnect from the units while in your
2187 terminal program by sending the escape-disconnect mentioned above.
2190 To set the radio frequency, use the 'c R' command to specify the
2191 radio transceiver configuration parameter. This parameter is computed
2192 using the desired frequency, 'F', the radio calibration parameter, 'C' (showed by the 'c s' command) and
2193 the standard calibration reference frequency, 'S', (normally 434.550MHz):
2197 Round the result to the nearest integer value.
2198 As with all 'c' sub-commands, follow this with a 'c w' to write the
2199 change to the parameter block in the on-board flash on
2200 your altimeter board if you want the change to stay in place across reboots.
2203 To set the apogee delay, use the 'c d' command.
2204 As with all 'c' sub-commands, follow this with a 'c w' to write the
2205 change to the parameter block in the on-board DataFlash chip.
2208 To set the main deployment altitude, use the 'c m' command.
2209 As with all 'c' sub-commands, follow this with a 'c w' to write the
2210 change to the parameter block in the on-board DataFlash chip.
2213 To calibrate the radio frequency, connect the UHF antenna port to a
2214 frequency counter, set the board to 434.550MHz, and use the 'C'
2215 command to generate a CW carrier. Wait for the transmitter temperature
2216 to stabilize and the frequency to settle down.
2217 Then, divide 434.550 MHz by the
2218 measured frequency and multiply by the current radio cal value show
2219 in the 'c s' command. For an unprogrammed board, the default value
2220 is 1186611. Take the resulting integer and program it using the 'c f'
2221 command. Testing with the 'C' command again should show a carrier
2222 within a few tens of Hertz of the intended frequency.
2223 As with all 'c' sub-commands, follow this with a 'c w' to write the
2224 change to the parameter block in the on-board DataFlash chip.
2227 Note that the 'reboot' command, which is very useful on the altimeters,
2228 will likely just cause problems with the dongle. The *correct* way
2229 to reset the dongle is just to unplug and re-plug it.
2232 A fun thing to do at the launch site and something you can do while
2233 learning how to use these units is to play with the radio link access
2234 between an altimeter and the TeleDongle. Be aware that you *must* create
2235 some physical separation between the devices, otherwise the link will
2236 not function due to signal overload in the receivers in each device.
2239 Now might be a good time to take a break and read the rest of this
2240 manual, particularly about the two "modes" that the altimeters
2241 can be placed in. TeleMetrum uses the position of the device when booting
2242 up will determine whether the unit is in "pad" or "idle" mode. TeleMini
2243 enters "idle" mode when it receives a command packet within the first 5 seconds
2244 of being powered up, otherwise it enters "pad" mode.
2247 You can access an altimeter in idle mode from the TeleDongle's USB
2248 connection using the radio link
2249 by issuing a 'p' command to the TeleDongle. Practice connecting and
2250 disconnecting ('~~' while using 'cu') from the altimeter. If
2251 you cannot escape out of the "p" command, (by using a '~~' when in
2252 CU) then it is likely that your kernel has issues. Try a newer version.
2255 Using this radio link allows you to configure the altimeter, test
2256 fire e-matches and igniters from the flight line, check pyro-match
2257 continuity and so forth. You can leave the unit turned on while it
2258 is in 'idle mode' and then place the
2259 rocket vertically on the launch pad, walk away and then issue a
2260 reboot command. The altimeter will reboot and start sending data
2261 having changed to the "pad" mode. If the TeleDongle is not receiving
2262 this data, you can disconnect 'cu' from the TeleDongle using the
2263 procedures mentioned above and THEN connect to the TeleDongle from
2264 inside 'ao-view'. If this doesn't work, disconnect from the
2265 TeleDongle, unplug it, and try again after plugging it back in.
2268 In order to reduce the chance of accidental firing of pyrotechnic
2269 charges, the command to fire a charge is intentionally somewhat
2270 difficult to type, and the built-in help is slightly cryptic to
2271 prevent accidental echoing of characters from the help text back at
2272 the board from firing a charge. The command to fire the apogee
2273 drogue charge is 'i DoIt drogue' and the command to fire the main
2274 charge is 'i DoIt main'.
2277 On TeleMetrum, the GPS will eventually find enough satellites, lock in on them,
2278 and 'ao-view' will both auditorily announce and visually indicate
2280 Now you can launch knowing that you have a good data path and
2281 good satellite lock for flight data and recovery. Remember
2282 you MUST tell ao-view to connect to the TeleDongle explicitly in
2283 order for ao-view to be able to receive data.
2286 The altimeters provide RDF (radio direction finding) tones on
2287 the pad, during descent and after landing. These can be used to
2288 locate the rocket using a directional antenna; the signal
2289 strength providing an indication of the direction from receiver to rocket.
2292 TeleMetrum also provides GPS tracking data, which can further simplify
2293 locating the rocket once it has landed. (The last good GPS data
2294 received before touch-down will be on the data screen of 'ao-view'.)
2297 Once you have recovered the rocket you can download the eeprom
2298 contents using either 'ao-dumplog' (or possibly 'ao-eeprom'), over
2299 either a USB cable or over the radio link using TeleDongle.
2300 And by following the man page for 'ao-postflight' you can create
2301 various data output reports, graphs, and even KML data to see the
2302 flight trajectory in Google-earth. (Moving the viewing angle making
2303 sure to connect the yellow lines while in Google-earth is the proper
2307 As for ao-view.... some things are in the menu but don't do anything
2308 very useful. The developers have stopped working on ao-view to focus
2309 on a new, cross-platform ground station program. So ao-view may or
2310 may not be updated in the future. Mostly you just use
2311 the Log and Device menus. It has a wonderful display of the incoming
2312 flight data and I am sure you will enjoy what it has to say to you
2313 once you enable the voice output!
2317 <title>Calibration</title>
2319 There are only two calibrations required for a TeleMetrum board, and
2320 only one for TeleDongle and TeleMini. All boards are shipped from
2321 the factory pre-calibrated, but the procedures are documented here
2322 in case they are ever needed. Re-calibration is not supported by
2323 AltosUI, you must connect to the board with a serial terminal program
2324 and interact directly with the on-board command interpreter to effect
2328 <title>Radio Frequency</title>
2330 The radio frequency is synthesized from a clock based on the 48 MHz
2331 crystal on the board. The actual frequency of this oscillator
2332 must be measured to generate a calibration constant. While our
2334 bandwidth is wide enough to allow boards to communicate even when
2335 their oscillators are not on exactly the same frequency, performance
2336 is best when they are closely matched.
2337 Radio frequency calibration requires a calibrated frequency counter.
2338 Fortunately, once set, the variation in frequency due to aging and
2339 temperature changes is small enough that re-calibration by customers
2340 should generally not be required.
2343 To calibrate the radio frequency, connect the UHF antenna port to a
2344 frequency counter, set the board to 434.550MHz, and use the 'C'
2345 command in the on-board command interpreter to generate a CW
2346 carrier. For TeleMetrum, this is best done over USB. For TeleMini,
2347 note that the only way to escape the 'C' command is via power cycle
2348 since the board will no longer be listening for commands once it
2349 starts generating a CW carrier.
2352 Wait for the transmitter temperature to stabilize and the frequency
2353 to settle down. Then, divide 434.550 MHz by the
2354 measured frequency and multiply by the current radio cal value show
2355 in the 'c s' command. For an unprogrammed board, the default value
2356 is 1186611. Take the resulting integer and program it using the 'c f'
2357 command. Testing with the 'C' command again should show a carrier
2358 within a few tens of Hertz of the intended frequency.
2359 As with all 'c' sub-commands, follow this with a 'c w' to write the
2360 change to the parameter block in the on-board DataFlash chip.
2363 Note that any time you re-do the radio frequency calibration, the
2364 radio frequency is reset to the default 434.550 Mhz. If you want
2365 to use another frequency, you will have to set that again after
2366 calibration is completed.
2370 <title>TeleMetrum Accelerometer</title>
2372 The TeleMetrum accelerometer we use has its own 5 volt power
2374 the output must be passed through a resistive voltage divider to match
2375 the input of our 3.3 volt ADC. This means that unlike the barometric
2376 sensor, the output of the acceleration sensor is not ratio-metric to
2377 the ADC converter, and calibration is required. Explicitly
2378 calibrating the accelerometers also allows us to load any device
2379 from a Freescale family that includes at least +/- 40g, 50g, 100g,
2380 and 200g parts. Using gravity,
2381 a simple 2-point calibration yields acceptable results capturing both
2382 the different sensitivities and ranges of the different accelerometer
2383 parts and any variation in power supply voltages or resistor values
2384 in the divider network.
2387 To calibrate the acceleration sensor, use the 'c a 0' command. You
2388 will be prompted to orient the board vertically with the UHF antenna
2389 up and press a key, then to orient the board vertically with the
2390 UHF antenna down and press a key. Note that the accuracy of this
2391 calibration depends primarily on how perfectly vertical and still
2392 the board is held during the cal process. As with all 'c'
2393 sub-commands, follow this with a 'c w' to write the
2394 change to the parameter block in the on-board DataFlash chip.
2397 The +1g and -1g calibration points are included in each telemetry
2398 frame and are part of the header stored in onboard flash to be
2399 downloaded after flight. We always store and return raw ADC
2400 samples for each sensor... so nothing is permanently "lost" or
2401 "damaged" if the calibration is poor.
2404 In the unlikely event an accel cal goes badly, it is possible
2405 that TeleMetrum may always come up in 'pad mode' and as such not be
2406 listening to either the USB or radio link. If that happens,
2407 there is a special hook in the firmware to force the board back
2408 in to 'idle mode' so you can re-do the cal. To use this hook, you
2409 just need to ground the SPI clock pin at power-on. This pin is
2410 available as pin 2 on the 8-pin companion connector, and pin 1 is
2411 ground. So either carefully install a fine-gauge wire jumper
2412 between the two pins closest to the index hole end of the 8-pin
2413 connector, or plug in the programming cable to the 8-pin connector
2414 and use a small screwdriver or similar to short the two pins closest
2415 to the index post on the 4-pin end of the programming cable, and
2416 power up the board. It should come up in 'idle mode' (two beeps),
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