1 <html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>TeleMetrum</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="book" title="TeleMetrum"><div class="titlepage"><div><div><h1 class="title"><a name="id2377993"></a>TeleMetrum</h1></div><div><h2 class="subtitle">Owner's Manual for the TeleMetrum System</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Bdale</span> <span class="surname">Garbee</span></h3></div></div><div><div class="author"><h3 class="author"><span class="firstname">Keith</span> <span class="surname">Packard</span></h3></div></div><div><p class="copyright">Copyright © 2010 Bdale Garbee and Keith Packard</p></div><div><div class="legalnotice" title="Legal Notice"><a name="id2661598"></a><p>
2 This document is released under the terms of the
3 <a class="ulink" href="http://creativecommons.org/licenses/by-sa/3.0/" target="_top">
4 Creative Commons ShareAlike 3.0
7 </p></div></div><div><div class="revhistory"><table border="1" width="100%" summary="Revision history"><tr><th align="left" valign="top" colspan="2"><b>Revision History</b></th></tr><tr><td align="left">Revision 0.2</td><td align="left">18 July 2010</td></tr><tr><td align="left" colspan="2">Significant update</td></tr><tr><td align="left">Revision 0.1</td><td align="left">30 March 2010</td></tr><tr><td align="left" colspan="2">Initial content</td></tr></table></div></div></div><hr></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="chapter"><a href="#id2641275">1. Introduction and Overview</a></span></dt><dt><span class="chapter"><a href="#id2656912">2. Getting Started</a></span></dt><dd><dl><dt><span class="section"><a href="#id2675548">FAQ</a></span></dt></dl></dd><dt><span class="chapter"><a href="#id2675022">3. Specifications</a></span></dt><dt><span class="chapter"><a href="#id2668775">4. Handling Precautions</a></span></dt><dt><span class="chapter"><a href="#id2640995">5. Hardware Overview</a></span></dt><dt><span class="chapter"><a href="#id2648902">6. Operation</a></span></dt><dd><dl><dt><span class="section"><a href="#id2645726">Firmware Modes </a></span></dt><dt><span class="section"><a href="#id2644773">GPS </a></span></dt><dt><span class="section"><a href="#id2659643">Ground Testing </a></span></dt><dt><span class="section"><a href="#id2657017">Radio Link </a></span></dt><dt><span class="section"><a href="#id2660834">Configurable Parameters</a></span></dt><dd><dl><dt><span class="section"><a href="#id2657184">Radio Channel</a></span></dt><dt><span class="section"><a href="#id2665037">Apogee Delay</a></span></dt><dt><span class="section"><a href="#id2670409">Main Deployment Altitude</a></span></dt></dl></dd><dt><span class="section"><a href="#id2666172">Calibration</a></span></dt><dd><dl><dt><span class="section"><a href="#id2676235">Radio Frequency</a></span></dt><dt><span class="section"><a href="#id2676108">Accelerometer</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#id2653312">7. Using Altus Metrum Products</a></span></dt><dd><dl><dt><span class="section"><a href="#id2645409">Being Legal</a></span></dt><dd><dl><dt><span class="section"><a href="#id2652849">In the Rocket</a></span></dt><dt><span class="section"><a href="#id2677187">On the Ground</a></span></dt><dt><span class="section"><a href="#id2679244">Data Analysis</a></span></dt><dt><span class="section"><a href="#id2668578">Future Plans</a></span></dt></dl></dd><dt><span class="section"><a href="#id2653941">
9 </a></span></dt></dl></dd></dl></div><div class="chapter" title="Chapter 1. Introduction and Overview"><div class="titlepage"><div><div><h2 class="title"><a name="id2641275"></a>Chapter 1. Introduction and Overview</h2></div></div></div><p>
10 Welcome to the Altus Metrum community! Our circuits and software reflect
11 our passion for both hobby rocketry and Free Software. We hope their
12 capabilities and performance will delight you in every way, but by
13 releasing all of our hardware and software designs under open licenses,
14 we also hope to empower you to take as active a role in our collective
17 The focal point of our community is TeleMetrum, a dual deploy altimeter
18 with fully integrated GPS and radio telemetry as standard features, and
19 a "companion interface" that will support optional capabilities in the
22 Complementing TeleMetrum is TeleDongle, a USB to RF interface for
23 communicating with TeleMetrum. Combined with your choice of antenna and
24 notebook computer, TeleDongle and our associated user interface software
25 form a complete ground station capable of logging and displaying in-flight
26 telemetry, aiding rocket recovery, then processing and archiving flight
27 data for analysis and review.
29 More products will be added to the Altus Metrum family over time, and
30 we currently envision that this will be a single, comprehensive manual
31 for the entire product family.
32 </p></div><div class="chapter" title="Chapter 2. Getting Started"><div class="titlepage"><div><div><h2 class="title"><a name="id2656912"></a>Chapter 2. Getting Started</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#id2675548">FAQ</a></span></dt></dl></div><p>
33 This chapter began as "The Mere-Mortals Quick Start/Usage Guide to
34 the Altus Metrum Starter Kit" by Bob Finch, W9YA, NAR 12965, TRA 12350,
35 w9ya@amsat.org. Bob was one of our first customers for a production
36 TeleMetrum, and the enthusiasm that led to his contribution of this
37 section is immensely gratifying and highy appreciated!
39 The first thing to do after you check the inventory of parts in your
40 "starter kit" is to charge the battery by plugging it into the
41 corresponding socket of the TeleMetrum and then using the USB A to B
42 cable to plug the Telemetrum into your computer's USB socket. The
43 TeleMetrum circuitry will charge the battery whenever it is plugged
44 into the usb socket. The TeleMetrum's on-off switch does NOT control
45 the charging circuitry. When the GPS chip is initially searching for
46 satellites, the unit will pull more current than it can pull from the
47 usb port, so the battery must be plugged in order to get a good
48 satellite lock. Once GPS is locked the current consumption goes back
49 down enough to enable charging while
50 running. So it's a good idea to fully charge the battery as your
51 first item of business so there is no issue getting and maintaining
52 satellite lock. The yellow charge indicator led will go out when the
53 battery is nearly full and the charger goes to trickle charge.
55 The other active device in the starter kit is the half-duplex TeleDongle
56 rf link. If you plug it in to your computer it should "just work",
57 showing up as a serial port device. If you are using Linux and are
58 having problems, try moving to a fresher kernel (2.6.33 or newer), as
59 there were some ugly USB serial driver bugs in earlier versions.
61 Next you should obtain and install the AltOS utilities. The first
62 generation sofware was written for Linux only. New software is coming
63 soon that will also run on Windows and Mac. For now, we'll concentrate
64 on Linux. If you are using Debian, an 'altos' package already exists,
65 see http://altusmetrum.org/AltOS for details on how to install it.
66 User-contributed directions for building packages on ArchLinux may be
67 found in the contrib/arch-linux directory as PKGBUILD files.
68 Between the debian/rules file and the PKGBUILD files in
69 contrib, you should find enough information to learn how to build the
70 software for any other version of Linux.
72 When you have successfully installed the software suite (either from
73 compiled source code or as the pre-built Debian package) you will
74 have 10 or so executable programs all of which have names beginning
76 ('ao-view' is the lone GUI-based program, the rest are command-line
77 oriented.) You will also have man pages, that give you basic info
79 You will also get this documentation in two file types in the doc/
80 directory, telemetrum-doc.pdf and telemetrum-doc.html.
81 Finally you will have a couple control files that allow the ao-view
82 GUI-based program to appear in your menu of programs (under
83 the 'Internet' category).
85 Both Telemetrum and TeleDongle can be directly communicated
86 with using USB ports. The first thing you should try after getting
87 both units plugged into to your computer's usb port(s) is to run
88 'ao-list' from a terminal-window to see what port-device-name each
89 device has been assigned by the operating system.
90 You will need this information to access the devices via their
91 respective on-board firmware and data using other command line
92 programs in the AltOS software suite.
94 To access the device's firmware for configuration you need a terminal
95 program such as you would use to talk to a modem. The software
96 authors prefer using the program 'cu' which comes from the UUCP package
97 on most Unix-like systems such as Linux. An example command line for
98 cu might be 'cu -l /dev/ttyACM0', substituting the correct number
99 indicated from running the
100 ao-list program. Another reasonable terminal program for Linux is
101 'cutecom'. The default 'escape'
102 character used by CU (i.e. the character you use to
103 issue commands to cu itself instead of sending the command as input
104 to the connected device) is a '~'. You will need this for use in
105 only two different ways during normal operations. First is to exit
106 the program by sending a '~.' which is called a 'escape-disconnect'
107 and allows you to close-out from 'cu'. The
108 second use will be outlined later.
110 Both TeleMetrum and TeleDongle share the concept of a two level
111 command set in their firmware.
112 The first layer has several single letter commands. Once
113 you are using 'cu' (or 'cutecom') sending (typing) a '?'
114 returns a full list of these
115 commands. The second level are configuration sub-commands accessed
116 using the 'c' command, for
117 instance typing 'c?' will give you this second level of commands
118 (all of which require the
119 letter 'c' to access). Please note that most configuration options
120 are stored only in DataFlash memory, and only TeleMetrum has this
121 memory to save the various values entered like the channel number
122 and your callsign when powered off. TeleDongle requires that you
123 set these each time you plug it in, which ao-view can help with.
125 Try setting these config ('c' or second level menu) values. A good
126 place to start is by setting your call sign. By default, the boards
127 use 'N0CALL' which is cute, but not exactly legal!
128 Spend a few minutes getting comfortable with the units, their
129 firmware, and 'cu' (or possibly 'cutecom').
130 For instance, try to send
131 (type) a 'c r 2' and verify the channel change by sending a 'c s'.
132 Verify you can connect and disconnect from the units while in your
133 terminal program by sending the escape-disconnect mentioned above.
135 Note that the 'reboot' command, which is very useful on TeleMetrum,
136 will likely just cause problems with the dongle. The *correct* way
137 to reset the dongle is just to unplug and re-plug it.
139 A fun thing to do at the launch site and something you can do while
140 learning how to use these units is to play with the rf-link access
141 of the TeleMetrum from the TeleDongle. Be aware that you *must* create
142 some physical separation between the devices, otherwise the link will
143 not function due to signal overload in the receivers in each device.
145 Now might be a good time to take a break and read the rest of this
146 manual, particularly about the two "modes" that the TeleMetrum
147 can be placed in and how the position of the TeleMetrum when booting
148 up will determine whether the unit is in "pad" or "idle" mode.
150 You can access a TeleMetrum in idle mode from the Teledongle's USB
151 connection using the rf link
152 by issuing a 'p' command to the TeleDongle. Practice connecting and
153 disconnecting ('~~' while using 'cu') from the TeleMetrum. If
154 you cannot escape out of the "p" command, (by using a '~~' when in
155 CU) then it is likely that your kernel has issues. Try a newer version.
157 Using this rf link allows you to configure the TeleMetrum, test
158 fire e-matches and igniters from the flight line, check pyro-match
159 continuity and so forth. You can leave the unit turned on while it
160 is in 'idle mode' and then place the
161 rocket vertically on the launch pad, walk away and then issue a
162 reboot command. The TeleMetrum will reboot and start sending data
163 having changed to the "pad" mode. If the TeleDongle is not receiving
164 this data, you can disconnect 'cu' from the Teledongle using the
165 procedures mentioned above and THEN connect to the TeleDongle from
166 inside 'ao-view'. If this doesn't work, disconnect from the
167 TeleDongle, unplug it, and try again after plugging it back in.
169 Eventually the GPS will find enough satellites, lock in on them,
170 and 'ao-view' will both auditorially announce and visually indicate
172 Now you can launch knowing that you have a good data path and
173 good satellite lock for flight data and recovery. Remember
174 you MUST tell ao-view to connect to the TeleDongle explicitly in
175 order for ao-view to be able to receive data.
177 Both RDF (radio direction finding) tones from the TeleMetrum and
178 GPS trekking data are available and together are very useful in
179 locating the rocket once it has landed. (The last good GPS data
180 received before touch-down will be on the data screen of 'ao-view'.)
182 Once you have recovered the rocket you can download the eeprom
183 contents using either 'ao-dumplog' (or possibly 'ao-eeprom'), over
184 either a USB cable or over the radio link using TeleDongle.
185 And by following the man page for 'ao-postflight' you can create
186 various data output reports, graphs, and even kml data to see the
187 flight trajectory in google-earth. (Moving the viewing angle making
188 sure to connect the yellow lines while in google-earth is the proper
191 As for ao-view.... some things are in the menu but don't do anything
192 very useful. The developers have stopped working on ao-view to focus
193 on a new, cross-platform ground station program. So ao-view may or
194 may not be updated in the future. Mostly you just use
195 the Log and Device menus. It has a wonderful display of the incoming
196 flight data and I am sure you will enjoy what it has to say to you
197 once you enable the voice output!
198 </p><div class="section" title="FAQ"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2675548"></a>FAQ</h2></div></div></div><p>
199 The altimeter (TeleMetrum) seems to shut off when disconnected from the
200 computer. Make sure the battery is adequately charged. Remember the
201 unit will pull more power than the USB port can deliver before the
202 GPS enters "locked" mode. The battery charges best when TeleMetrum
205 It's impossible to stop the TeleDongle when it's in "p" mode, I have
206 to unplug the USB cable? Make sure you have tried to "escape out" of
207 this mode. If this doesn't work the reboot procedure for the
208 TeleDongle *is* to simply unplug it. 'cu' however will retain it's
209 outgoing buffer IF your "escape out" ('~~') does not work.
210 At this point using either 'ao-view' (or possibly
211 'cutemon') instead of 'cu' will 'clear' the issue and allow renewed
214 The amber LED (on the TeleMetrum/altimeter) lights up when both
215 battery and USB are connected. Does this mean it's charging?
216 Yes, the yellow LED indicates the charging at the 'regular' rate.
217 If the led is out but the unit is still plugged into a USB port,
218 then the battery is being charged at a 'trickle' rate.
220 There are no "dit-dah-dah-dit" sound like the manual mentions?
221 That's the "pad" mode. Weak batteries might be the problem.
222 It is also possible that the unit is horizontal and the output
223 is instead a "dit-dit" meaning 'idle'.
225 It's unclear how to use 'ao-view' and other programs when 'cu'
226 is running. You cannot have more than one program connected to
227 the TeleDongle at one time without apparent data loss as the
228 incoming data will not make it to both programs intact.
229 Disconnect whatever programs aren't currently being used.
231 How do I save flight data?
232 Live telemetry is written to file(s) whenever 'ao-view' is connected
233 to the TeleDongle. The file area defaults to ~/altos
234 but is easily changed using the menus in 'ao-view'. The files that
235 are written end in '.telem'. The after-flight
236 data-dumped files will end in .eeprom and represent continuous data
237 unlike the rf-linked .telem files that are subject to the
238 turnarounds/data-packaging time slots in the half-duplex rf data path.
239 See the above instructions on what and how to save the eeprom stored
240 data after physically retrieving your TeleMetrum. Make sure to save
241 the on-board data after each flight, as the current firmware will
242 over-write any previous flight data during a new flight.
243 </p></div></div><div class="chapter" title="Chapter 3. Specifications"><div class="titlepage"><div><div><h2 class="title"><a name="id2675022"></a>Chapter 3. Specifications</h2></div></div></div><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
244 Recording altimeter for model rocketry.
245 </p></li><li class="listitem"><p>
246 Supports dual deployment (can fire 2 ejection charges).
247 </p></li><li class="listitem"><p>
248 70cm ham-band transceiver for telemetry downlink.
249 </p></li><li class="listitem"><p>
250 Barometric pressure sensor good to 45k feet MSL.
251 </p></li><li class="listitem"><p>
252 1-axis high-g accelerometer for motor characterization, capable of
253 +/- 50g using default part.
254 </p></li><li class="listitem"><p>
255 On-board, integrated GPS receiver with 5hz update rate capability.
256 </p></li><li class="listitem"><p>
257 On-board 1 megabyte non-volatile memory for flight data storage.
258 </p></li><li class="listitem"><p>
259 USB interface for battery charging, configuration, and data recovery.
260 </p></li><li class="listitem"><p>
261 Fully integrated support for LiPo rechargeable batteries.
262 </p></li><li class="listitem"><p>
263 Uses LiPo to fire e-matches, support for optional separate pyro
265 </p></li><li class="listitem"><p>
266 2.75 x 1 inch board designed to fit inside 29mm airframe coupler tube.
267 </p></li></ul></div></div><div class="chapter" title="Chapter 4. Handling Precautions"><div class="titlepage"><div><div><h2 class="title"><a name="id2668775"></a>Chapter 4. Handling Precautions</h2></div></div></div><p>
268 TeleMetrum is a sophisticated electronic device. When handled gently and
269 properly installed in an airframe, it will deliver impressive results.
270 However, like all electronic devices, there are some precautions you
273 The Lithium Polymer rechargeable batteries used with TeleMetrum have an
274 extraordinary power density. This is great because we can fly with
275 much less battery mass than if we used alkaline batteries or previous
276 generation rechargeable batteries... but if they are punctured
277 or their leads are allowed to short, they can and will release their
279 Thus we recommend that you take some care when handling our batteries
280 and consider giving them some extra protection in your airframe. We
281 often wrap them in suitable scraps of closed-cell packing foam before
282 strapping them down, for example.
284 The TeleMetrum barometric sensor is sensitive to sunlight. In normal
285 mounting situations, it and all of the other surface mount components
286 are "down" towards whatever the underlying mounting surface is, so
287 this is not normally a problem. Please consider this, though, when
288 designing an installation, for example, in a 29mm airframe with a
289 see-through plastic payload bay.
291 The TeleMetrum barometric sensor sampling port must be able to
293 both by not being covered by foam or tape or other materials that might
294 directly block the hole on the top of the sensor, but also by having a
295 suitable static vent to outside air.
297 As with all other rocketry electronics, TeleMetrum must be protected
298 from exposure to corrosive motor exhaust and ejection charge gasses.
299 </p></div><div class="chapter" title="Chapter 5. Hardware Overview"><div class="titlepage"><div><div><h2 class="title"><a name="id2640995"></a>Chapter 5. Hardware Overview</h2></div></div></div><p>
300 TeleMetrum is a 1 inch by 2.75 inch circuit board. It was designed to
301 fit inside coupler for 29mm airframe tubing, but using it in a tube that
302 small in diameter may require some creativity in mounting and wiring
303 to succeed! The default 1/4
304 wave UHF wire antenna attached to the center of the nose-cone end of
305 the board is about 7 inches long, and wiring for a power switch and
306 the e-matches for apogee and main ejection charges depart from the
307 fin can end of the board. Given all this, an ideal "simple" avionics
308 bay for TeleMetrum should have at least 10 inches of interior length.
310 A typical TeleMetrum installation using the on-board GPS antenna and
311 default wire UHF antenna involves attaching only a suitable
312 Lithium Polymer battery, a single pole switch for power on/off, and
313 two pairs of wires connecting e-matches for the apogee and main ejection
316 By default, we use the unregulated output of the LiPo battery directly
317 to fire ejection charges. This works marvelously with standard
318 low-current e-matches like the J-Tek from MJG Technologies, and with
319 Quest Q2G2 igniters. However, if you
320 want or need to use a separate pyro battery, you can do so by adding
321 a second 2mm connector to position B2 on the board and cutting the
322 thick pcb trace connecting the LiPo battery to the pyro circuit between
323 the two silk screen marks on the surface mount side of the board shown
326 We offer two choices of pyro and power switch connector, or you can
327 choose neither and solder wires directly to the board. All three choices
328 are reasonable depending on the constraints of your airframe. Our
329 favorite option when there is sufficient room above the board is to use
330 the Tyco pin header with polarization and locking. If you choose this
331 option, you crimp individual wires for the power switch and e-matches
332 into a mating connector, and installing and removing the TeleMetrum
333 board from an airframe is as easy as plugging or unplugging two
334 connectors. If the airframe will not support this much height or if
335 you want to be able to directly attach e-match leads to the board, we
336 offer a screw terminal block. This is very similar to what most other
337 altimeter vendors provide and so may be the most familiar option.
338 You'll need a very small straight blade screwdriver to connect
339 and disconnect the board in this case, such as you might find in a
340 jeweler's screwdriver set. Finally, you can forego both options and
341 solder wires directly to the board, which may be the best choice for
342 minimum diameter and/or minimum mass designs.
344 For most airframes, the integrated GPS antenna and wire UHF antenna are
345 a great combination. However, if you are installing in a carbon-fiber
346 electronics bay which is opaque to RF signals, you may need to use
347 off-board external antennas instead. In this case, you can order
348 TeleMetrum with an SMA connector for the UHF antenna connection, and
349 you can unplug the integrated GPS antenna and select an appropriate
350 off-board GPS antenna with cable terminating in a U.FL connector.
351 </p></div><div class="chapter" title="Chapter 6. Operation"><div class="titlepage"><div><div><h2 class="title"><a name="id2648902"></a>Chapter 6. Operation</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#id2645726">Firmware Modes </a></span></dt><dt><span class="section"><a href="#id2644773">GPS </a></span></dt><dt><span class="section"><a href="#id2659643">Ground Testing </a></span></dt><dt><span class="section"><a href="#id2657017">Radio Link </a></span></dt><dt><span class="section"><a href="#id2660834">Configurable Parameters</a></span></dt><dd><dl><dt><span class="section"><a href="#id2657184">Radio Channel</a></span></dt><dt><span class="section"><a href="#id2665037">Apogee Delay</a></span></dt><dt><span class="section"><a href="#id2670409">Main Deployment Altitude</a></span></dt></dl></dd><dt><span class="section"><a href="#id2666172">Calibration</a></span></dt><dd><dl><dt><span class="section"><a href="#id2676235">Radio Frequency</a></span></dt><dt><span class="section"><a href="#id2676108">Accelerometer</a></span></dt></dl></dd></dl></div><div class="section" title="Firmware Modes"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2645726"></a>Firmware Modes </h2></div></div></div><p>
352 The AltOS firmware build for TeleMetrum has two fundamental modes,
353 "idle" and "flight". Which of these modes the firmware operates in
354 is determined by the orientation of the rocket (well, actually the
355 board, of course...) at the time power is switched on. If the rocket
356 is "nose up", then TeleMetrum assumes it's on a rail or rod being
357 prepared for launch, so the firmware chooses flight mode. However,
358 if the rocket is more or less horizontal, the firmware instead enters
361 At power on, you will hear three beeps
362 ("S" in Morse code for startup) and then a pause while
363 TeleMetrum completes initialization and self tests, and decides which
366 In flight or "pad" mode, TeleMetrum turns on the GPS system,
368 state machine, goes into transmit-only mode on the RF link sending
369 telemetry, and waits for launch to be detected. Flight mode is
370 indicated by an audible "di-dah-dah-dit" ("P" for pad) on the
372 beeps indicating the state of the pyrotechnic igniter continuity.
373 One beep indicates apogee continuity, two beeps indicate
374 main continuity, three beeps indicate both apogee and main continuity,
375 and one longer "brap" sound indicates no continuity. For a dual
376 deploy flight, make sure you're getting three beeps before launching!
377 For apogee-only or motor eject flights, do what makes sense.
379 In idle mode, you will hear an audible "di-dit" ("I" for idle), and
380 the normal flight state machine is disengaged, thus
381 no ejection charges will fire. TeleMetrum also listens on the RF
382 link when in idle mode for packet mode requests sent from TeleDongle.
383 Commands can be issued to a TeleMetrum in idle mode over either
384 USB or the RF link equivalently.
385 Idle mode is useful for configuring TeleMetrum, for extracting data
386 from the on-board storage chip after flight, and for ground testing
389 One "neat trick" of particular value when TeleMetrum is used with very
390 large airframes, is that you can power the board up while the rocket
391 is horizontal, such that it comes up in idle mode. Then you can
392 raise the airframe to launch position, use a TeleDongle to open
393 a packet connection, and issue a 'reset' command which will cause
394 TeleMetrum to reboot, realize it's now nose-up, and thus choose
395 flight mode. This is much safer than standing on the top step of a
396 rickety step-ladder or hanging off the side of a launch tower with
397 a screw-driver trying to turn on your avionics before installing
399 </p></div><div class="section" title="GPS"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2644773"></a>GPS </h2></div></div></div><p>
400 TeleMetrum includes a complete GPS receiver. See a later section for
401 a brief explanation of how GPS works that will help you understand
402 the information in the telemetry stream. The bottom line is that
403 the TeleMetrum GPS receiver needs to lock onto at least four
404 satellites to obtain a solid 3 dimensional position fix and know
407 TeleMetrum provides backup power to the GPS chip any time a LiPo
408 battery is connected. This allows the receiver to "warm start" on
409 the launch rail much faster than if every power-on were a "cold start"
410 for the GPS receiver. In typical operations, powering up TeleMetrum
411 on the flight line in idle mode while performing final airframe
412 preparation will be sufficient to allow the GPS receiver to cold
413 start and acquire lock. Then the board can be powered down during
414 RSO review and installation on a launch rod or rail. When the board
415 is turned back on, the GPS system should lock very quickly, typically
416 long before igniter installation and return to the flight line are
418 </p></div><div class="section" title="Ground Testing"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2659643"></a>Ground Testing </h2></div></div></div><p>
419 An important aspect of preparing a rocket using electronic deployment
420 for flight is ground testing the recovery system. Thanks
421 to the bi-directional RF link central to the Altus Metrum system,
422 this can be accomplished in a TeleMetrum-equipped rocket without as
423 much work as you may be accustomed to with other systems. It can
426 Just prep the rocket for flight, then power up TeleMetrum while the
427 airframe is horizontal. This will cause the firmware to go into
428 "idle" mode, in which the normal flight state machine is disabled and
429 charges will not fire without manual command. Then, establish an
430 RF packet connection from a TeleDongle-equipped computer using the
431 P command from a safe distance. You can now command TeleMetrum to
432 fire the apogee or main charges to complete your testing.
434 In order to reduce the chance of accidental firing of pyrotechnic
435 charges, the command to fire a charge is intentionally somewhat
436 difficult to type, and the built-in help is slightly cryptic to
437 prevent accidental echoing of characters from the help text back at
438 the board from firing a charge. The command to fire the apogee
439 drogue charge is 'i DoIt drogue' and the command to fire the main
440 charge is 'i DoIt main'.
441 </p></div><div class="section" title="Radio Link"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2657017"></a>Radio Link </h2></div></div></div><p>
442 The chip our boards are based on incorporates an RF transceiver, but
443 it's not a full duplex system... each end can only be transmitting or
444 receiving at any given moment. So we had to decide how to manage the
447 By design, TeleMetrum firmware listens for an RF connection when
448 it's in "idle mode" (turned on while the rocket is horizontal), which
449 allows us to use the RF link to configure the rocket, do things like
450 ejection tests, and extract data after a flight without having to
451 crack open the airframe. However, when the board is in "flight
452 mode" (turned on when the rocket is vertical) the TeleMetrum only
453 transmits and doesn't listen at all. That's because we want to put
454 ultimate priority on event detection and getting telemetry out of
455 the rocket and out over
456 the RF link in case the rocket crashes and we aren't able to extract
459 We don't use a 'normal packet radio' mode because they're just too
460 inefficient. The GFSK modulation we use is just FSK with the
461 baseband pulses passed through a
462 Gaussian filter before they go into the modulator to limit the
463 transmitted bandwidth. When combined with the hardware forward error
464 correction support in the cc1111 chip, this allows us to have a very
465 robust 38.4 kilobit data link with only 10 milliwatts of transmit power,
466 a whip antenna in the rocket, and a hand-held Yagi on the ground. We've
467 had flights to above 21k feet AGL with good reception, and calculations
468 suggest we should be good to well over 40k feet AGL with a 5-element yagi on
469 the ground. We hope to fly boards to higher altitudes soon, and would
470 of course appreciate customer feedback on performance in higher
472 </p></div><div class="section" title="Configurable Parameters"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2660834"></a>Configurable Parameters</h2></div></div></div><p>
473 Configuring a TeleMetrum board for flight is very simple. Because we
474 have both acceleration and pressure sensors, there is no need to set
475 a "mach delay", for example. The few configurable parameters can all
476 be set using a simple terminal program over the USB port or RF link
478 </p><div class="section" title="Radio Channel"><div class="titlepage"><div><div><h3 class="title"><a name="id2657184"></a>Radio Channel</h3></div></div></div><p>
479 Our firmware supports 10 channels. The default channel 0 corresponds
480 to a center frequency of 434.550 Mhz, and channels are spaced every
481 100 khz. Thus, channel 1 is 434.650 Mhz, and channel 9 is 435.550 Mhz.
482 At any given launch, we highly recommend coordinating who will use
483 each channel and when to avoid interference. And of course, both
484 TeleMetrum and TeleDongle must be configured to the same channel to
485 successfully communicate with each other.
487 To set the radio channel, use the 'c r' command, like 'c r 3' to set
489 As with all 'c' sub-commands, follow this with a 'c w' to write the
490 change to the parameter block in the on-board DataFlash chip on
491 your TeleMetrum board if you want the change to stay in place across reboots.
492 </p></div><div class="section" title="Apogee Delay"><div class="titlepage"><div><div><h3 class="title"><a name="id2665037"></a>Apogee Delay</h3></div></div></div><p>
493 Apogee delay is the number of seconds after TeleMetrum detects flight
494 apogee that the drogue charge should be fired. In most cases, this
495 should be left at the default of 0. However, if you are flying
496 redundant electronics such as for an L3 certification, you may wish
497 to set one of your altimeters to a positive delay so that both
498 primary and backup pyrotechnic charges do not fire simultaneously.
500 To set the apogee delay, use the [FIXME] command.
501 As with all 'c' sub-commands, follow this with a 'c w' to write the
502 change to the parameter block in the on-board DataFlash chip.
504 Please note that the TeleMetrum apogee detection algorithm always
505 fires a fraction of a second *after* apogee. If you are also flying
506 an altimeter like the PerfectFlite MAWD, which only supports selecting
507 0 or 1 seconds of apogee delay, you may wish to set the MAWD to 0
508 seconds delay and set the TeleMetrum to fire your backup 2 or 3
509 seconds later to avoid any chance of both charges firing
510 simultaneously. We've flown several airframes this way quite happily,
511 including Keith's successful L3 cert.
512 </p></div><div class="section" title="Main Deployment Altitude"><div class="titlepage"><div><div><h3 class="title"><a name="id2670409"></a>Main Deployment Altitude</h3></div></div></div><p>
513 By default, TeleMetrum will fire the main deployment charge at an
514 elevation of 250 meters (about 820 feet) above ground. We think this
515 is a good elevation for most airframes, but feel free to change this
516 to suit. In particular, if you are flying two altimeters, you may
518 deployment elevation for the backup altimeter to be something lower
519 than the primary so that both pyrotechnic charges don't fire
522 To set the main deployment altitude, use the [FIXME] command.
523 As with all 'c' sub-commands, follow this with a 'c w' to write the
524 change to the parameter block in the on-board DataFlash chip.
525 </p></div></div><div class="section" title="Calibration"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2666172"></a>Calibration</h2></div></div></div><p>
526 There are only two calibrations required for a TeleMetrum board, and
527 only one for TeleDongle.
528 </p><div class="section" title="Radio Frequency"><div class="titlepage"><div><div><h3 class="title"><a name="id2676235"></a>Radio Frequency</h3></div></div></div><p>
529 The radio frequency is synthesized from a clock based on the 48 Mhz
530 crystal on the board. The actual frequency of this oscillator must be
531 measured to generate a calibration constant. While our GFSK modulation
532 bandwidth is wide enough to allow boards to communicate even when
533 their oscillators are not on exactly the same frequency, performance
534 is best when they are closely matched.
535 Radio frequency calibration requires a calibrated frequency counter.
536 Fortunately, once set, the variation in frequency due to aging and
537 temperature changes is small enough that re-calibration by customers
538 should generally not be required.
540 To calibrate the radio frequency, connect the UHF antenna port to a
541 frequency counter, set the board to channel 0, and use the 'C'
542 command to generate a CW carrier. Wait for the transmitter temperature
543 to stabilize and the frequency to settle down.
544 Then, divide 434.550 Mhz by the
545 measured frequency and multiply by the current radio cal value show
546 in the 'c s' command. For an unprogrammed board, the default value
547 is 1186611. Take the resulting integer and program it using the 'c f'
548 command. Testing with the 'C' command again should show a carrier
549 within a few tens of Hertz of the intended frequency.
550 As with all 'c' sub-commands, follow this with a 'c w' to write the
551 change to the parameter block in the on-board DataFlash chip.
552 </p></div><div class="section" title="Accelerometer"><div class="titlepage"><div><div><h3 class="title"><a name="id2676108"></a>Accelerometer</h3></div></div></div><p>
553 The accelerometer we use has its own 5 volt power supply and
554 the output must be passed through a resistive voltage divider to match
555 the input of our 3.3 volt ADC. This means that unlike the barometric
556 sensor, the output of the acceleration sensor is not ratiometric to
557 the ADC converter, and calibration is required. We also support the
558 use of any of several accelerometers from a Freescale family that
559 includes at least +/- 40g, 50g, 100g, and 200g parts. Using gravity,
560 a simple 2-point calibration yields acceptable results capturing both
561 the different sensitivities and ranges of the different accelerometer
562 parts and any variation in power supply voltages or resistor values
563 in the divider network.
565 To calibrate the acceleration sensor, use the 'c a 0' command. You
566 will be prompted to orient the board vertically with the UHF antenna
567 up and press a key, then to orient the board vertically with the
568 UHF antenna down and press a key.
569 As with all 'c' sub-commands, follow this with a 'c w' to write the
570 change to the parameter block in the on-board DataFlash chip.
572 The +1g and -1g calibration points are included in each telemetry
573 frame and are part of the header extracted by ao-dumplog after flight.
574 Note that we always store and return raw ADC samples for each
575 sensor... nothing is permanently "lost" or "damaged" if the
577 </p></div></div></div><div class="chapter" title="Chapter 7. Using Altus Metrum Products"><div class="titlepage"><div><div><h2 class="title"><a name="id2653312"></a>Chapter 7. Using Altus Metrum Products</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#id2645409">Being Legal</a></span></dt><dd><dl><dt><span class="section"><a href="#id2652849">In the Rocket</a></span></dt><dt><span class="section"><a href="#id2677187">On the Ground</a></span></dt><dt><span class="section"><a href="#id2679244">Data Analysis</a></span></dt><dt><span class="section"><a href="#id2668578">Future Plans</a></span></dt></dl></dd><dt><span class="section"><a href="#id2653941">
579 </a></span></dt></dl></div><div class="section" title="Being Legal"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2645409"></a>Being Legal</h2></div></div></div><p>
580 First off, in the US, you need an [amateur radio license](../Radio) or
581 other authorization to legally operate the radio transmitters that are part
583 </p><div class="section" title="In the Rocket"><div class="titlepage"><div><div><h3 class="title"><a name="id2652849"></a>In the Rocket</h3></div></div></div><p>
584 In the rocket itself, you just need a [TeleMetrum](../TeleMetrum) board and
585 a LiPo rechargeable battery. An 860mAh battery weighs less than a 9V
586 alkaline battery, and will run a [TeleMetrum](../TeleMetrum) for hours.
588 By default, we ship TeleMetrum with a simple wire antenna. If your
589 electronics bay or the airframe it resides within is made of carbon fiber,
590 which is opaque to RF signals, you may choose to have an SMA connector
591 installed so that you can run a coaxial cable to an antenna mounted
592 elsewhere in the rocket.
593 </p></div><div class="section" title="On the Ground"><div class="titlepage"><div><div><h3 class="title"><a name="id2677187"></a>On the Ground</h3></div></div></div><p>
594 To receive the data stream from the rocket, you need an antenna and short
595 feedline connected to one of our [TeleDongle](../TeleDongle) units. The
596 TeleDongle in turn plugs directly into the USB port on a notebook
597 computer. Because TeleDongle looks like a simple serial port, your computer
598 does not require special device drivers... just plug it in.
600 Right now, all of our application software is written for Linux. However,
601 because we understand that many people run Windows or MacOS, we are working
602 on a new ground station program written in Java that should work on all
605 After the flight, you can use the RF link to extract the more detailed data
606 logged in the rocket, or you can use a mini USB cable to plug into the
607 TeleMetrum board directly. Pulling out the data without having to open up
608 the rocket is pretty cool! A USB cable is also how you charge the LiPo
609 battery, so you'll want one of those anyway... the same cable used by lots
610 of digital cameras and other modern electronic stuff will work fine.
612 If your rocket lands out of sight, you may enjoy having a hand-held GPS
613 receiver, so that you can put in a waypoint for the last reported rocket
614 position before touch-down. This makes looking for your rocket a lot like
615 Geo-Cacheing... just go to the waypoint and look around starting from there.
617 You may also enjoy having a ham radio "HT" that covers the 70cm band... you
618 can use that with your antenna to direction-find the rocket on the ground
619 the same way you can use a Walston or Beeline tracker. This can be handy
620 if the rocket is hiding in sage brush or a tree, or if the last GPS position
621 doesn't get you close enough because the rocket dropped into a canyon, or
622 the wind is blowing it across a dry lake bed, or something like that... Keith
623 and Bdale both currently own and use the Yaesu VX-7R at launches.
625 So, to recap, on the ground the hardware you'll need includes:
626 </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
627 an antenna and feedline
628 </li><li class="listitem">
630 </li><li class="listitem">
632 </li><li class="listitem">
633 optionally, a handheld GPS receiver
634 </li><li class="listitem">
635 optionally, an HT or receiver covering 435 Mhz
638 The best hand-held commercial directional antennas we've found for radio
639 direction finding rockets are from
640 <a class="ulink" href="http://www.arrowantennas.com/" target="_top">
643 The 440-3 and 440-5 are both good choices for finding a
644 TeleMetrum-equipped rocket when used with a suitable 70cm HT.
645 </p></div><div class="section" title="Data Analysis"><div class="titlepage"><div><div><h3 class="title"><a name="id2679244"></a>Data Analysis</h3></div></div></div><p>
646 Our software makes it easy to log the data from each flight, both the
647 telemetry received over the RF link during the flight itself, and the more
648 complete data log recorded in the DataFlash memory on the TeleMetrum
649 board. Once this data is on your computer, our postflight tools make it
650 easy to quickly get to the numbers everyone wants, like apogee altitude,
651 max acceleration, and max velocity. You can also generate and view a
652 standard set of plots showing the altitude, acceleration, and
653 velocity of the rocket during flight. And you can even export a data file
654 useable with Google Maps and Google Earth for visualizing the flight path
655 in two or three dimensions!
657 Our ultimate goal is to emit a set of files for each flight that can be
658 published as a web page per flight, or just viewed on your local disk with
660 </p></div><div class="section" title="Future Plans"><div class="titlepage"><div><div><h3 class="title"><a name="id2668578"></a>Future Plans</h3></div></div></div><p>
661 In the future, we intend to offer "companion boards" for the rocket that will
662 plug in to TeleMetrum to collect additional data, provide more pyro channels,
663 and so forth. A reference design for a companion board will be documented
664 soon, and will be compatible with open source Arduino programming tools.
666 We are also working on the design of a hand-held ground terminal that will
667 allow monitoring the rocket's status, collecting data during flight, and
668 logging data after flight without the need for a notebook computer on the
669 flight line. Particularly since it is so difficult to read most notebook
670 screens in direct sunlight, we think this will be a great thing to have.
672 Because all of our work is open, both the hardware designs and the software,
673 if you have some great idea for an addition to the current Altus Metrum family,
674 feel free to dive in and help! Or let us know what you'd like to see that
675 we aren't already working on, and maybe we'll get excited about it too...
676 </p></div></div><div class="section" title="How GPS Works"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2653941"></a>
678 </h2></div></div></div><p>
680 </p></div></div></div></body></html>
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