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2 <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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5 <title>TeleMetrum</title>
6 <subtitle>Owner's Manual for the TeleMetrum System</subtitle>
9 <firstname>Bdale</firstname>
10 <surname>Garbee</surname>
13 <firstname>Keith</firstname>
14 <surname>Packard</surname>
18 <holder>Bdale Garbee and Keith Packard</holder>
22 This document is released under the terms of the
23 <ulink url="http://creativecommons.org/licenses/by-sa/3.0/">
24 Creative Commons ShareAlike 3.0
31 <revnumber>0.2</revnumber>
32 <date>18 July 2010</date>
33 <revremark>Significant update</revremark>
36 <revnumber>0.1</revnumber>
37 <date>30 March 2010</date>
38 <revremark>Initial content</revremark>
43 <title>Introduction and Overview</title>
45 Welcome to the Altus Metrum community! Our circuits and software reflect
46 our passion for both hobby rocketry and Free Software. We hope their
47 capabilities and performance will delight you in every way, but by
48 releasing all of our hardware and software designs under open licenses,
49 we also hope to empower you to take as active a role in our collective
53 The focal point of our community is TeleMetrum, a dual deploy altimeter
54 with fully integrated GPS and radio telemetry as standard features, and
55 a "companion interface" that will support optional capabilities in the
59 Complementing TeleMetrum is TeleDongle, a USB to RF interface for
60 communicating with TeleMetrum. Combined with your choice of antenna and
61 notebook computer, TeleDongle and our associated user interface software
62 form a complete ground station capable of logging and displaying in-flight
63 telemetry, aiding rocket recovery, then processing and archiving flight
64 data for analysis and review.
67 More products will be added to the Altus Metrum family over time, and
68 we currently envision that this will be a single, comprehensive manual
69 for the entire product family.
73 <title>Getting Started</title>
75 This chapter began as "The Mere-Mortals Quick Start/Usage Guide to
76 the Altus Metrum Starter Kit" by Bob Finch, W9YA, NAR 12965, TRA 12350,
77 w9ya@amsat.org. Bob was one of our first customers for a production
78 TeleMetrum, and the enthusiasm that led to his contribution of this
79 section is immensely gratifying and highy appreciated!
82 The first thing to do after you check the inventory of parts in your
83 "starter kit" is to charge the battery by plugging it into the
84 corresponding socket of the TeleMetrum and then using the USB A to B
85 cable to plug the Telemetrum into your computer's USB socket. The
86 TeleMetrum circuitry will charge the battery whenever it is plugged
87 into the usb socket. The TeleMetrum's on-off switch does NOT control
88 the charging circuitry. When the GPS chip is initially searching for
89 satellites, the unit will pull more current than it can pull from the
90 usb port, so the battery must be plugged in order to get a good
91 satellite lock. Once GPS is locked the current consumption goes back
92 down enough to enable charging while
93 running. So it's a good idea to fully charge the battery as your
94 first item of business so there is no issue getting and maintaining
95 satellite lock. The yellow charge indicator led will go out when the
96 battery is nearly full and the charger goes to trickle charge.
99 The other active device in the starter kit is the half-duplex TeleDongle
100 rf link. If you plug it in to your computer it should "just work",
101 showing up as a serial port device. If you are using Linux and are
102 having problems, try moving to a fresher kernel (2.6.33 or newer), as
103 there were some ugly USB serial driver bugs in earlier versions.
106 Next you should obtain and install the AltOS utilities. The first
107 generation sofware was written for Linux only. New software is coming
108 soon that will also run on Windows and Mac. For now, we'll concentrate
109 on Linux. If you are using Debian, an 'altos' package already exists,
110 see http://altusmetrum.org/AltOS for details on how to install it.
111 User-contributed directions for building packages on ArchLinux may be
112 found in the contrib/arch-linux directory as PKGBUILD files.
113 Between the debian/rules file and the PKGBUILD files in
114 contrib, you should find enough information to learn how to build the
115 software for any other version of Linux.
118 When you have successfully installed the software suite (either from
119 compiled source code or as the pre-built Debian package) you will
120 have 10 or so executable programs all of which have names beginning
122 ('ao-view' is the lone GUI-based program, the rest are command-line
123 oriented.) You will also have man pages, that give you basic info
125 You will also get this documentation in two file types in the doc/
126 directory, telemetrum-doc.pdf and telemetrum-doc.html.
127 Finally you will have a couple control files that allow the ao-view
128 GUI-based program to appear in your menu of programs (under
129 the 'Internet' category).
132 Both Telemetrum and TeleDongle can be directly communicated
133 with using USB ports. The first thing you should try after getting
134 both units plugged into to your computer's usb port(s) is to run
135 'ao-list' from a terminal-window to see what port-device-name each
136 device has been assigned by the operating system.
137 You will need this information to access the devices via their
138 respective on-board firmware and data using other command line
139 programs in the AltOS software suite.
142 To access the device's firmware for configuration you need a terminal
143 program such as you would use to talk to a modem. The software
144 authors prefer using the program 'cu' which comes from the UUCP package
145 on most Unix-like systems such as Linux. An example command line for
146 cu might be 'cu -l /dev/ttyACM0', substituting the correct number
147 indicated from running the
148 ao-list program. Another reasonable terminal program for Linux is
149 'cutecom'. The default 'escape'
150 character used by CU (i.e. the character you use to
151 issue commands to cu itself instead of sending the command as input
152 to the connected device) is a '~'. You will need this for use in
153 only two different ways during normal operations. First is to exit
154 the program by sending a '~.' which is called a 'escape-disconnect'
155 and allows you to close-out from 'cu'. The
156 second use will be outlined later.
159 Both TeleMetrum and TeleDongle share the concept of a two level
160 command set in their firmware.
161 The first layer has several single letter commands. Once
162 you are using 'cu' (or 'cutecom') sending (typing) a '?'
163 returns a full list of these
164 commands. The second level are configuration sub-commands accessed
165 using the 'c' command, for
166 instance typing 'c?' will give you this second level of commands
167 (all of which require the
168 letter 'c' to access). Please note that most configuration options
169 are stored only in DataFlash memory, and only TeleMetrum has this
170 memory to save the various values entered like the channel number
171 and your callsign when powered off. TeleDongle requires that you
172 set these each time you plug it in, which ao-view can help with.
175 Try setting these config ('c' or second level menu) values. A good
176 place to start is by setting your call sign. By default, the boards
177 use 'N0CALL' which is cute, but not exactly legal!
178 Spend a few minutes getting comfortable with the units, their
179 firmware, and 'cu' (or possibly 'cutecom').
180 For instance, try to send
181 (type) a 'c r 2' and verify the channel change by sending a 'c s'.
182 Verify you can connect and disconnect from the units while in your
183 terminal program by sending the escape-disconnect mentioned above.
186 Note that the 'reboot' command, which is very useful on TeleMetrum,
187 will likely just cause problems with the dongle. The *correct* way
188 to reset the dongle is just to unplug and re-plug it.
191 A fun thing to do at the launch site and something you can do while
192 learning how to use these units is to play with the rf-link access
193 of the TeleMetrum from the TeleDongle. Be aware that you *must* create
194 some physical separation between the devices, otherwise the link will
195 not function due to signal overload in the receivers in each device.
198 Now might be a good time to take a break and read the rest of this
199 manual, particularly about the two "modes" that the TeleMetrum
200 can be placed in and how the position of the TeleMetrum when booting
201 up will determine whether the unit is in "pad" or "idle" mode.
204 You can access a TeleMetrum in idle mode from the Teledongle's USB
205 connection using the rf link
206 by issuing a 'p' command to the TeleDongle. Practice connecting and
207 disconnecting ('~~' while using 'cu') from the TeleMetrum. If
208 you cannot escape out of the "p" command, (by using a '~~' when in
209 CU) then it is likely that your kernel has issues. Try a newer version.
212 Using this rf link allows you to configure the TeleMetrum, test
213 fire e-matches and igniters from the flight line, check pyro-match
214 continuity and so forth. You can leave the unit turned on while it
215 is in 'idle mode' and then place the
216 rocket vertically on the launch pad, walk away and then issue a
217 reboot command. The TeleMetrum will reboot and start sending data
218 having changed to the "pad" mode. If the TeleDongle is not receiving
219 this data, you can disconnect 'cu' from the Teledongle using the
220 procedures mentioned above and THEN connect to the TeleDongle from
221 inside 'ao-view'. If this doesn't work, disconnect from the
222 TeleDongle, unplug it, and try again after plugging it back in.
225 Eventually the GPS will find enough satellites, lock in on them,
226 and 'ao-view' will both auditorially announce and visually indicate
228 Now you can launch knowing that you have a good data path and
229 good satellite lock for flight data and recovery. Remember
230 you MUST tell ao-view to connect to the TeleDongle explicitly in
231 order for ao-view to be able to receive data.
234 Both RDF (radio direction finding) tones from the TeleMetrum and
235 GPS trekking data are available and together are very useful in
236 locating the rocket once it has landed. (The last good GPS data
237 received before touch-down will be on the data screen of 'ao-view'.)
240 Once you have recovered the rocket you can download the eeprom
241 contents using either 'ao-dumplog' (or possibly 'ao-eeprom'), over
242 either a USB cable or over the radio link using TeleDongle.
243 And by following the man page for 'ao-postflight' you can create
244 various data output reports, graphs, and even kml data to see the
245 flight trajectory in google-earth. (Moving the viewing angle making
246 sure to connect the yellow lines while in google-earth is the proper
250 As for ao-view.... some things are in the menu but don't do anything
251 very useful. The developers have stopped working on ao-view to focus
252 on a new, cross-platform ground station program. So ao-view may or
253 may not be updated in the future. Mostly you just use
254 the Log and Device menus. It has a wonderful display of the incoming
255 flight data and I am sure you will enjoy what it has to say to you
256 once you enable the voice output!
261 The altimeter (TeleMetrum) seems to shut off when disconnected from the
262 computer. Make sure the battery is adequately charged. Remember the
263 unit will pull more power than the USB port can deliver before the
264 GPS enters "locked" mode. The battery charges best when TeleMetrum
268 It's impossible to stop the TeleDongle when it's in "p" mode, I have
269 to unplug the USB cable? Make sure you have tried to "escape out" of
270 this mode. If this doesn't work the reboot procedure for the
271 TeleDongle *is* to simply unplug it. 'cu' however will retain it's
272 outgoing buffer IF your "escape out" ('~~') does not work.
273 At this point using either 'ao-view' (or possibly
274 'cutemon') instead of 'cu' will 'clear' the issue and allow renewed
278 The amber LED (on the TeleMetrum/altimeter) lights up when both
279 battery and USB are connected. Does this mean it's charging?
280 Yes, the yellow LED indicates the charging at the 'regular' rate.
281 If the led is out but the unit is still plugged into a USB port,
282 then the battery is being charged at a 'trickle' rate.
285 There are no "dit-dah-dah-dit" sound like the manual mentions?
286 That's the "pad" mode. Weak batteries might be the problem.
287 It is also possible that the unit is horizontal and the output
288 is instead a "dit-dit" meaning 'idle'.
291 It's unclear how to use 'ao-view' and other programs when 'cu'
292 is running. You cannot have more than one program connected to
293 the TeleDongle at one time without apparent data loss as the
294 incoming data will not make it to both programs intact.
295 Disconnect whatever programs aren't currently being used.
298 How do I save flight data?
299 Live telemetry is written to file(s) whenever 'ao-view' is connected
300 to the TeleDongle. The file area defaults to ~/altos
301 but is easily changed using the menus in 'ao-view'. The files that
302 are written end in '.telem'. The after-flight
303 data-dumped files will end in .eeprom and represent continuous data
304 unlike the rf-linked .telem files that are subject to the
305 turnarounds/data-packaging time slots in the half-duplex rf data path.
306 See the above instructions on what and how to save the eeprom stored
307 data after physically retrieving your TeleMetrum. Make sure to save
308 the on-board data after each flight, as the current firmware will
309 over-write any previous flight data during a new flight.
314 <title>Specifications</title>
318 Recording altimeter for model rocketry.
323 Supports dual deployment (can fire 2 ejection charges).
328 70cm ham-band transceiver for telemetry downlink.
333 Barometric pressure sensor good to 45k feet MSL.
338 1-axis high-g accelerometer for motor characterization, capable of
339 +/- 50g using default part.
344 On-board, integrated GPS receiver with 5hz update rate capability.
349 On-board 1 megabyte non-volatile memory for flight data storage.
354 USB interface for battery charging, configuration, and data recovery.
359 Fully integrated support for LiPo rechargeable batteries.
364 Uses LiPo to fire e-matches, support for optional separate pyro
370 2.75 x 1 inch board designed to fit inside 29mm airframe coupler tube.
376 <title>Handling Precautions</title>
378 TeleMetrum is a sophisticated electronic device. When handled gently and
379 properly installed in an airframe, it will deliver impressive results.
380 However, like all electronic devices, there are some precautions you
384 The Lithium Polymer rechargeable batteries used with TeleMetrum have an
385 extraordinary power density. This is great because we can fly with
386 much less battery mass than if we used alkaline batteries or previous
387 generation rechargeable batteries... but if they are punctured
388 or their leads are allowed to short, they can and will release their
390 Thus we recommend that you take some care when handling our batteries
391 and consider giving them some extra protection in your airframe. We
392 often wrap them in suitable scraps of closed-cell packing foam before
393 strapping them down, for example.
396 The TeleMetrum barometric sensor is sensitive to sunlight. In normal
397 mounting situations, it and all of the other surface mount components
398 are "down" towards whatever the underlying mounting surface is, so
399 this is not normally a problem. Please consider this, though, when
400 designing an installation, for example, in a 29mm airframe with a
401 see-through plastic payload bay.
404 The TeleMetrum barometric sensor sampling port must be able to
406 both by not being covered by foam or tape or other materials that might
407 directly block the hole on the top of the sensor, but also by having a
408 suitable static vent to outside air.
411 As with all other rocketry electronics, TeleMetrum must be protected
412 from exposure to corrosive motor exhaust and ejection charge gasses.
416 <title>Hardware Overview</title>
418 TeleMetrum is a 1 inch by 2.75 inch circuit board. It was designed to
419 fit inside coupler for 29mm airframe tubing, but using it in a tube that
420 small in diameter may require some creativity in mounting and wiring
421 to succeed! The default 1/4
422 wave UHF wire antenna attached to the center of the nose-cone end of
423 the board is about 7 inches long, and wiring for a power switch and
424 the e-matches for apogee and main ejection charges depart from the
425 fin can end of the board. Given all this, an ideal "simple" avionics
426 bay for TeleMetrum should have at least 10 inches of interior length.
429 A typical TeleMetrum installation using the on-board GPS antenna and
430 default wire UHF antenna involves attaching only a suitable
431 Lithium Polymer battery, a single pole switch for power on/off, and
432 two pairs of wires connecting e-matches for the apogee and main ejection
436 By default, we use the unregulated output of the LiPo battery directly
437 to fire ejection charges. This works marvelously with standard
438 low-current e-matches like the J-Tek from MJG Technologies, and with
439 Quest Q2G2 igniters. However, if you
440 want or need to use a separate pyro battery, you can do so by adding
441 a second 2mm connector to position B2 on the board and cutting the
442 thick pcb trace connecting the LiPo battery to the pyro circuit between
443 the two silk screen marks on the surface mount side of the board shown
447 We offer two choices of pyro and power switch connector, or you can
448 choose neither and solder wires directly to the board. All three choices
449 are reasonable depending on the constraints of your airframe. Our
450 favorite option when there is sufficient room above the board is to use
451 the Tyco pin header with polarization and locking. If you choose this
452 option, you crimp individual wires for the power switch and e-matches
453 into a mating connector, and installing and removing the TeleMetrum
454 board from an airframe is as easy as plugging or unplugging two
455 connectors. If the airframe will not support this much height or if
456 you want to be able to directly attach e-match leads to the board, we
457 offer a screw terminal block. This is very similar to what most other
458 altimeter vendors provide and so may be the most familiar option.
459 You'll need a very small straight blade screwdriver to connect
460 and disconnect the board in this case, such as you might find in a
461 jeweler's screwdriver set. Finally, you can forego both options and
462 solder wires directly to the board, which may be the best choice for
463 minimum diameter and/or minimum mass designs.
466 For most airframes, the integrated GPS antenna and wire UHF antenna are
467 a great combination. However, if you are installing in a carbon-fiber
468 electronics bay which is opaque to RF signals, you may need to use
469 off-board external antennas instead. In this case, you can order
470 TeleMetrum with an SMA connector for the UHF antenna connection, and
471 you can unplug the integrated GPS antenna and select an appropriate
472 off-board GPS antenna with cable terminating in a U.FL connector.
476 <title>Operation</title>
478 <title>Firmware Modes </title>
480 The AltOS firmware build for TeleMetrum has two fundamental modes,
481 "idle" and "flight". Which of these modes the firmware operates in
482 is determined by the orientation of the rocket (well, actually the
483 board, of course...) at the time power is switched on. If the rocket
484 is "nose up", then TeleMetrum assumes it's on a rail or rod being
485 prepared for launch, so the firmware chooses flight mode. However,
486 if the rocket is more or less horizontal, the firmware instead enters
490 At power on, you will hear three beeps
491 ("S" in Morse code for startup) and then a pause while
492 TeleMetrum completes initialization and self tests, and decides which
496 In flight or "pad" mode, TeleMetrum turns on the GPS system,
498 state machine, goes into transmit-only mode on the RF link sending
499 telemetry, and waits for launch to be detected. Flight mode is
500 indicated by an audible "di-dah-dah-dit" ("P" for pad) on the
502 beeps indicating the state of the pyrotechnic igniter continuity.
503 One beep indicates apogee continuity, two beeps indicate
504 main continuity, three beeps indicate both apogee and main continuity,
505 and one longer "brap" sound indicates no continuity. For a dual
506 deploy flight, make sure you're getting three beeps before launching!
507 For apogee-only or motor eject flights, do what makes sense.
510 In idle mode, you will hear an audible "di-dit" ("I" for idle), and
511 the normal flight state machine is disengaged, thus
512 no ejection charges will fire. TeleMetrum also listens on the RF
513 link when in idle mode for packet mode requests sent from TeleDongle.
514 Commands can be issued to a TeleMetrum in idle mode over either
515 USB or the RF link equivalently.
516 Idle mode is useful for configuring TeleMetrum, for extracting data
517 from the on-board storage chip after flight, and for ground testing
521 One "neat trick" of particular value when TeleMetrum is used with very
522 large airframes, is that you can power the board up while the rocket
523 is horizontal, such that it comes up in idle mode. Then you can
524 raise the airframe to launch position, use a TeleDongle to open
525 a packet connection, and issue a 'reset' command which will cause
526 TeleMetrum to reboot, realize it's now nose-up, and thus choose
527 flight mode. This is much safer than standing on the top step of a
528 rickety step-ladder or hanging off the side of a launch tower with
529 a screw-driver trying to turn on your avionics before installing
536 TeleMetrum includes a complete GPS receiver. See a later section for
537 a brief explanation of how GPS works that will help you understand
538 the information in the telemetry stream. The bottom line is that
539 the TeleMetrum GPS receiver needs to lock onto at least four
540 satellites to obtain a solid 3 dimensional position fix and know
544 TeleMetrum provides backup power to the GPS chip any time a LiPo
545 battery is connected. This allows the receiver to "warm start" on
546 the launch rail much faster than if every power-on were a "cold start"
547 for the GPS receiver. In typical operations, powering up TeleMetrum
548 on the flight line in idle mode while performing final airframe
549 preparation will be sufficient to allow the GPS receiver to cold
550 start and acquire lock. Then the board can be powered down during
551 RSO review and installation on a launch rod or rail. When the board
552 is turned back on, the GPS system should lock very quickly, typically
553 long before igniter installation and return to the flight line are
558 <title>Ground Testing </title>
560 An important aspect of preparing a rocket using electronic deployment
561 for flight is ground testing the recovery system. Thanks
562 to the bi-directional RF link central to the Altus Metrum system,
563 this can be accomplished in a TeleMetrum-equipped rocket without as
564 much work as you may be accustomed to with other systems. It can
568 Just prep the rocket for flight, then power up TeleMetrum while the
569 airframe is horizontal. This will cause the firmware to go into
570 "idle" mode, in which the normal flight state machine is disabled and
571 charges will not fire without manual command. Then, establish an
572 RF packet connection from a TeleDongle-equipped computer using the
573 P command from a safe distance. You can now command TeleMetrum to
574 fire the apogee or main charges to complete your testing.
577 In order to reduce the chance of accidental firing of pyrotechnic
578 charges, the command to fire a charge is intentionally somewhat
579 difficult to type, and the built-in help is slightly cryptic to
580 prevent accidental echoing of characters from the help text back at
581 the board from firing a charge. The command to fire the apogee
582 drogue charge is 'i DoIt drogue' and the command to fire the main
583 charge is 'i DoIt main'.
587 <title>Radio Link </title>
589 The chip our boards are based on incorporates an RF transceiver, but
590 it's not a full duplex system... each end can only be transmitting or
591 receiving at any given moment. So we had to decide how to manage the
595 By design, TeleMetrum firmware listens for an RF connection when
596 it's in "idle mode" (turned on while the rocket is horizontal), which
597 allows us to use the RF link to configure the rocket, do things like
598 ejection tests, and extract data after a flight without having to
599 crack open the airframe. However, when the board is in "flight
600 mode" (turned on when the rocket is vertical) the TeleMetrum only
601 transmits and doesn't listen at all. That's because we want to put
602 ultimate priority on event detection and getting telemetry out of
603 the rocket and out over
604 the RF link in case the rocket crashes and we aren't able to extract
608 We don't use a 'normal packet radio' mode because they're just too
609 inefficient. The GFSK modulation we use is just FSK with the
610 baseband pulses passed through a
611 Gaussian filter before they go into the modulator to limit the
612 transmitted bandwidth. When combined with the hardware forward error
613 correction support in the cc1111 chip, this allows us to have a very
614 robust 38.4 kilobit data link with only 10 milliwatts of transmit power,
615 a whip antenna in the rocket, and a hand-held Yagi on the ground. We've
616 had flights to above 21k feet AGL with good reception, and calculations
617 suggest we should be good to well over 40k feet AGL with a 5-element yagi on
618 the ground. We hope to fly boards to higher altitudes soon, and would
619 of course appreciate customer feedback on performance in higher
624 <title>Configurable Parameters</title>
626 Configuring a TeleMetrum board for flight is very simple. Because we
627 have both acceleration and pressure sensors, there is no need to set
628 a "mach delay", for example. The few configurable parameters can all
629 be set using a simple terminal program over the USB port or RF link
633 <title>Radio Channel</title>
635 Our firmware supports 10 channels. The default channel 0 corresponds
636 to a center frequency of 434.550 Mhz, and channels are spaced every
637 100 khz. Thus, channel 1 is 434.650 Mhz, and channel 9 is 435.550 Mhz.
638 At any given launch, we highly recommend coordinating who will use
639 each channel and when to avoid interference. And of course, both
640 TeleMetrum and TeleDongle must be configured to the same channel to
641 successfully communicate with each other.
644 To set the radio channel, use the 'c r' command, like 'c r 3' to set
646 As with all 'c' sub-commands, follow this with a 'c w' to write the
647 change to the parameter block in the on-board DataFlash chip on
648 your TeleMetrum board if you want the change to stay in place across reboots.
652 <title>Apogee Delay</title>
654 Apogee delay is the number of seconds after TeleMetrum detects flight
655 apogee that the drogue charge should be fired. In most cases, this
656 should be left at the default of 0. However, if you are flying
657 redundant electronics such as for an L3 certification, you may wish
658 to set one of your altimeters to a positive delay so that both
659 primary and backup pyrotechnic charges do not fire simultaneously.
662 To set the apogee delay, use the [FIXME] command.
663 As with all 'c' sub-commands, follow this with a 'c w' to write the
664 change to the parameter block in the on-board DataFlash chip.
667 Please note that the TeleMetrum apogee detection algorithm always
668 fires a fraction of a second *after* apogee. If you are also flying
669 an altimeter like the PerfectFlite MAWD, which only supports selecting
670 0 or 1 seconds of apogee delay, you may wish to set the MAWD to 0
671 seconds delay and set the TeleMetrum to fire your backup 2 or 3
672 seconds later to avoid any chance of both charges firing
673 simultaneously. We've flown several airframes this way quite happily,
674 including Keith's successful L3 cert.
678 <title>Main Deployment Altitude</title>
680 By default, TeleMetrum will fire the main deployment charge at an
681 elevation of 250 meters (about 820 feet) above ground. We think this
682 is a good elevation for most airframes, but feel free to change this
683 to suit. In particular, if you are flying two altimeters, you may
685 deployment elevation for the backup altimeter to be something lower
686 than the primary so that both pyrotechnic charges don't fire
690 To set the main deployment altitude, use the [FIXME] command.
691 As with all 'c' sub-commands, follow this with a 'c w' to write the
692 change to the parameter block in the on-board DataFlash chip.
697 <title>Calibration</title>
699 There are only two calibrations required for a TeleMetrum board, and
700 only one for TeleDongle.
703 <title>Radio Frequency</title>
705 The radio frequency is synthesized from a clock based on the 48 Mhz
706 crystal on the board. The actual frequency of this oscillator must be
707 measured to generate a calibration constant. While our GFSK modulation
708 bandwidth is wide enough to allow boards to communicate even when
709 their oscillators are not on exactly the same frequency, performance
710 is best when they are closely matched.
711 Radio frequency calibration requires a calibrated frequency counter.
712 Fortunately, once set, the variation in frequency due to aging and
713 temperature changes is small enough that re-calibration by customers
714 should generally not be required.
717 To calibrate the radio frequency, connect the UHF antenna port to a
718 frequency counter, set the board to channel 0, and use the 'C'
719 command to generate a CW carrier. Wait for the transmitter temperature
720 to stabilize and the frequency to settle down.
721 Then, divide 434.550 Mhz by the
722 measured frequency and multiply by the current radio cal value show
723 in the 'c s' command. For an unprogrammed board, the default value
724 is 1186611. Take the resulting integer and program it using the 'c f'
725 command. Testing with the 'C' command again should show a carrier
726 within a few tens of Hertz of the intended frequency.
727 As with all 'c' sub-commands, follow this with a 'c w' to write the
728 change to the parameter block in the on-board DataFlash chip.
732 <title>Accelerometer</title>
734 The accelerometer we use has its own 5 volt power supply and
735 the output must be passed through a resistive voltage divider to match
736 the input of our 3.3 volt ADC. This means that unlike the barometric
737 sensor, the output of the acceleration sensor is not ratiometric to
738 the ADC converter, and calibration is required. We also support the
739 use of any of several accelerometers from a Freescale family that
740 includes at least +/- 40g, 50g, 100g, and 200g parts. Using gravity,
741 a simple 2-point calibration yields acceptable results capturing both
742 the different sensitivities and ranges of the different accelerometer
743 parts and any variation in power supply voltages or resistor values
744 in the divider network.
747 To calibrate the acceleration sensor, use the 'c a 0' command. You
748 will be prompted to orient the board vertically with the UHF antenna
749 up and press a key, then to orient the board vertically with the
750 UHF antenna down and press a key.
751 As with all 'c' sub-commands, follow this with a 'c w' to write the
752 change to the parameter block in the on-board DataFlash chip.
755 The +1g and -1g calibration points are included in each telemetry
756 frame and are part of the header extracted by ao-dumplog after flight.
757 Note that we always store and return raw ADC samples for each
758 sensor... nothing is permanently "lost" or "damaged" if the
765 <title>Using Altus Metrum Products</title>
767 <title>Being Legal</title>
769 First off, in the US, you need an [amateur radio license](../Radio) or
770 other authorization to legally operate the radio transmitters that are part
774 <title>In the Rocket</title>
776 In the rocket itself, you just need a [TeleMetrum](../TeleMetrum) board and
777 a LiPo rechargeable battery. An 860mAh battery weighs less than a 9V
778 alkaline battery, and will run a [TeleMetrum](../TeleMetrum) for hours.
781 By default, we ship TeleMetrum with a simple wire antenna. If your
782 electronics bay or the airframe it resides within is made of carbon fiber,
783 which is opaque to RF signals, you may choose to have an SMA connector
784 installed so that you can run a coaxial cable to an antenna mounted
785 elsewhere in the rocket.
789 <title>On the Ground</title>
791 To receive the data stream from the rocket, you need an antenna and short
792 feedline connected to one of our [TeleDongle](../TeleDongle) units. The
793 TeleDongle in turn plugs directly into the USB port on a notebook
794 computer. Because TeleDongle looks like a simple serial port, your computer
795 does not require special device drivers... just plug it in.
798 Right now, all of our application software is written for Linux. However,
799 because we understand that many people run Windows or MacOS, we are working
800 on a new ground station program written in Java that should work on all
804 After the flight, you can use the RF link to extract the more detailed data
805 logged in the rocket, or you can use a mini USB cable to plug into the
806 TeleMetrum board directly. Pulling out the data without having to open up
807 the rocket is pretty cool! A USB cable is also how you charge the LiPo
808 battery, so you'll want one of those anyway... the same cable used by lots
809 of digital cameras and other modern electronic stuff will work fine.
812 If your rocket lands out of sight, you may enjoy having a hand-held GPS
813 receiver, so that you can put in a waypoint for the last reported rocket
814 position before touch-down. This makes looking for your rocket a lot like
815 Geo-Cacheing... just go to the waypoint and look around starting from there.
818 You may also enjoy having a ham radio "HT" that covers the 70cm band... you
819 can use that with your antenna to direction-find the rocket on the ground
820 the same way you can use a Walston or Beeline tracker. This can be handy
821 if the rocket is hiding in sage brush or a tree, or if the last GPS position
822 doesn't get you close enough because the rocket dropped into a canyon, or
823 the wind is blowing it across a dry lake bed, or something like that... Keith
824 and Bdale both currently own and use the Yaesu VX-7R at launches.
827 So, to recap, on the ground the hardware you'll need includes:
828 <orderedlist inheritnum='inherit' numeration='arabic'>
830 an antenna and feedline
839 optionally, a handheld GPS receiver
842 optionally, an HT or receiver covering 435 Mhz
847 The best hand-held commercial directional antennas we've found for radio
848 direction finding rockets are from
849 <ulink url="http://www.arrowantennas.com/" >
852 The 440-3 and 440-5 are both good choices for finding a
853 TeleMetrum-equipped rocket when used with a suitable 70cm HT.
857 <title>Data Analysis</title>
859 Our software makes it easy to log the data from each flight, both the
860 telemetry received over the RF link during the flight itself, and the more
861 complete data log recorded in the DataFlash memory on the TeleMetrum
862 board. Once this data is on your computer, our postflight tools make it
863 easy to quickly get to the numbers everyone wants, like apogee altitude,
864 max acceleration, and max velocity. You can also generate and view a
865 standard set of plots showing the altitude, acceleration, and
866 velocity of the rocket during flight. And you can even export a data file
867 useable with Google Maps and Google Earth for visualizing the flight path
868 in two or three dimensions!
871 Our ultimate goal is to emit a set of files for each flight that can be
872 published as a web page per flight, or just viewed on your local disk with
877 <title>Future Plans</title>
879 In the future, we intend to offer "companion boards" for the rocket that will
880 plug in to TeleMetrum to collect additional data, provide more pyro channels,
881 and so forth. A reference design for a companion board will be documented
882 soon, and will be compatible with open source Arduino programming tools.
885 We are also working on the design of a hand-held ground terminal that will
886 allow monitoring the rocket's status, collecting data during flight, and
887 logging data after flight without the need for a notebook computer on the
888 flight line. Particularly since it is so difficult to read most notebook
889 screens in direct sunlight, we think this will be a great thing to have.
892 Because all of our work is open, both the hardware designs and the software,
893 if you have some great idea for an addition to the current Altus Metrum family,
894 feel free to dive in and help! Or let us know what you'd like to see that
895 we aren't already working on, and maybe we'll get excited about it too...