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="id2681233"></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="id2964839"></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 0.1</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="#id2961261">1. Introduction and Overview</a></span></dt><dt><span class="chapter"><a href="#id2945012">2. Getting Started</a></span></dt><dd><dl><dt><span class="section"><a href="#id2969939">FAQ</a></span></dt></dl></dd><dt><span class="chapter"><a href="#id2963754">3. Specifications</a></span></dt><dt><span class="chapter"><a href="#id2965995">4. Handling Precautions</a></span></dt><dt><span class="chapter"><a href="#id2979951">5. Hardware Overview</a></span></dt><dt><span class="chapter"><a href="#id2980270">6. Operation</a></span></dt><dd><dl><dt><span class="section"><a href="#id2966264">Firmware Modes </a></span></dt><dt><span class="section"><a href="#id2965911">GPS </a></span></dt><dt><span class="section"><a href="#id2977993">Ground Testing </a></span></dt><dt><span class="section"><a href="#id2962884">Radio Link </a></span></dt><dt><span class="section"><a href="#id2960257">Configurable Parameters</a></span></dt><dd><dl><dt><span class="section"><a href="#id2955134">Radio Channel</a></span></dt><dt><span class="section"><a href="#id2948360">Apogee Delay</a></span></dt><dt><span class="section"><a href="#id2982412">Main Deployment Altitude</a></span></dt></dl></dd><dt><span class="section"><a href="#id2969053">Calibration</a></span></dt><dd><dl><dt><span class="section"><a href="#id2969214">Radio Frequency</a></span></dt><dt><span class="section"><a href="#id2975078">Accelerometer</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#id2976467">7. Using Altus Metrum Products</a></span></dt><dd><dl><dt><span class="section"><a href="#id2964669">Being Legal</a></span></dt><dd><dl><dt><span class="section"><a href="#id2969459">In the Rocket</a></span></dt><dt><span class="section"><a href="#id2964682">On the Ground</a></span></dt><dt><span class="section"><a href="#id2980718">Data Analysis</a></span></dt><dt><span class="section"><a href="#id2957709">Future Plans</a></span></dt></dl></dd><dt><span class="section"><a href="#id2961256">
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="id2961261"></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.
28 </p></div><div class="chapter" title="Chapter 2. Getting Started"><div class="titlepage"><div><div><h2 class="title"><a name="id2945012"></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="#id2969939">FAQ</a></span></dt></dl></div><p>
29 This chapter began as "The Mere-Mortals Quick Start/Usage Guide to
30 the Altus Metrum Starter Kit" by Bob Finch, W9YA, NAR 12965, TRA 12350,
31 w9ya@amsat.org. Bob was one of our first customers for a production
32 TeleMetrum, and the enthusiasm that led to his contribution of this
33 section is immensely gratifying and highy appreciated!
35 The first thing to do after you check the inventory of parts in your
36 "starter kit" is to charge the battery by plugging it into the
37 corresponding socket of the TeleMetrum and then using the USB A to B
38 cable to plug the Telemetrum into your computer's USB socket. The
39 TeleMetrum circuitry will charge the battery whenever it is plugged
40 into the usb socket. The TeleMetrum's on-off switch does NOT control
41 the charging circuitry. When the GPS chip is initially searching for
42 satellites, the unit will pull more current than it can pull from the
43 usb port, so the battery must be plugged in order to get a good
44 satellite lock. Once GPS is locked the current consumption goes back
45 down enough to enable charging while
46 running. So it's a good idea to fully charge the battery as your
47 first item of business so there is no issue getting and maintaining
48 satellite lock. The yellow charge indicator led will go out when the
49 battery is nearly full and the charger goes to trickle charge.
51 The other active device in the starter kit is the half-duplex TeleDongle
52 rf link. If you plug it in to your computer it should "just work",
53 showing up as a serial port device. If you are using Linux and are
54 having problems, try moving to a fresher kernel (2.6.33 or newer), as
55 there were some ugly USB serial driver bugs in earlier versions.
57 Next you should obtain and install the AltOS utilities. The first
58 generation sofware was written for Linux only. New software is coming
59 soon that will also run on Windows and Mac. For now, we'll concentrate
60 on Linux. If you are using Debian, an 'altos' package already exists,
61 see http://altusmetrum.org/AltOS for details on how to install it.
62 User-contributed directions for building packages on ArchLinux may be
63 found in the contrib/arch-linux directory as PKGBUILD files.
64 Between the debian/rules file and the PKGBUILD files in
65 contrib, you should find enough information to learn how to build the
66 software for any other version of Linux.
68 When you have successfully installed the software suite (either from
69 compiled source code or as the pre-built Debian package) you will
70 have 10 executable programs all of which have names beginning with 'ao-'.
71 ('ao-view' is the lone GUI-based program.
72 The rest are command-line based.) You will also
73 have 10 man pages, that give you basic info on each program.
74 And you will also get this documentation in two file types,
75 telemetrum.pdf and telemetrum.html.
76 Finally you will have a couple of control files that allow the ao-view
77 GUI-based program to appear in your menu of programs (under
78 the 'Internet' category).
80 Both Telemetrum and TeleDongle can be directly communicated
81 with using USB ports. The first thing you should try after getting
82 both units plugged into to your computer's usb port(s) is to run
83 'ao-list' from a terminal-window (I use konsole for this,) to see what
84 port-device-name each device has been assigned by the operating system.
85 You will need this information to access the devices via their
86 respective on-board firmware and data using other command line
87 programs in the AltOS software suite.
89 To access the device's firmware for configuration you need a terminal
90 program such as you would use to talk to a modem. The software
91 authors prefer using the program 'cu' which comes from the UUCP package
92 on most Unix-like systems such as Linux. An example command line for
93 cu might be 'cu -l /dev/ttyACM0', substituting the correct number
94 indicated from running the
95 ao-list program. Another reasonable terminal program for Linux is
96 'cutecom'. The default 'escape'
97 character used by CU (i.e. the character you use to
98 issue commands to cu itself instead of sending the command as input
99 to the connected device) is a '~'. You will need this for use in
100 only two different ways during normal operations. First is to exit
101 the program by sending a '~.' which is called a 'escape-disconnect'
102 and allows you to close-out from 'cu'. The
103 second use will be outlined later.
105 Both TeleMetrum and TeleDongle share the concept of a two level
107 firmware. The first layer has several single letter commands. Once
108 you are using 'cu' (or 'cutecom') sending (typing) a '?'
109 returns a full list of these
110 commands. The second level are configuration sub-commands accessed
111 using the 'c' command, for
112 instance typing 'c?' will give you this second level of commands
113 (all of which require the
114 letter 'c' to access). Please note that most configuration options
115 are stored only in DataFlash memory, and only TeleMetrum has this
116 memory to save the various values entered like the channel number
117 and your callsign when powered off. TeleDongle requires that you
118 set these each time you plug it in, which ao-view can help with.
120 Try setting these config ('c' or second level menu) values. A good
121 place to start is by setting your call sign. By default, the boards
122 use 'N0CALL' which is cute, but not exactly legal!
123 Spend a few minutes getting comfortable with the units, their
124 firmware, 'cu' (and possibly 'cutecom') For instance, try to send
125 (type) a 'cr2' and verify the channel change by sending a 'cs'.
126 Verify you can connect and disconnect from the units while in 'cu'
127 by sending the escape-disconnect mentioned above.
129 Note that the 'reboot' command, which is very useful on TeleMetrum,
130 will likely just cause problems with the dongle. The *correct* way
131 to reset the dongle is just to unplug and re-plug it.
133 A fun thing to do at the launch site and something you can do while
134 learning how to use these units is to play with the rf-link access
135 of the TeleMetrum from the TeleDongle. Be aware that you *must* create
136 some physical separation between the devices, otherwise the link will
137 not function due to signal overload in the receivers in each device.
139 Now might be a good time to take a break and read the rest of this
140 manual, particularly about the two "modes" that the TeleMetrum
141 can be placed in and how the position of the TeleMetrum when booting
142 up will determine whether the unit is in "pad" or "idle" mode.
144 You can access a TeleMetrum in idle mode from the Teledongle's USB
145 connection using the rf link
146 by issuing a 'p' command to the TeleDongle. Practice connecting and
147 disconnecting ('~~' while using 'cu') from the TeleMetrum. If
148 you cannot escape out of the "p" command, (by using a '~~' when in
149 CU) then it is likely that your kernel has issues. Try a newer version.
151 Using this rf link allows you to configure the TeleMetrum, test
152 fire e-matches and igniters from the flight line, check pyro-match
153 continuity and so forth. You can leave the unit turned on while it
154 is in 'idle mode' and then place the
155 rocket vertically on the launch pad, walk away and then issue a
156 reboot command. The TeleMetrum will reboot and start sending data
157 having changed to the "pad" mode. If the TeleDongle is not receiving
158 this data, you can disconnect 'cu' from the Teledongle using the
159 procedures mentioned above and THEN connect to the TeleDongle from
160 inside 'ao-view'. If this doesn't work, disconnect from the
161 TeleDongle, unplug it, and try again after plugging it back in.
163 Eventually the GPS will find enough satellites, lock in on them,
164 and 'ao-view' will both auditorially announce and visually indicate
166 Now you can launch knowing that you have a good data path and
167 good satellite lock for flight data and recovery. Remember
168 you MUST tell ao-view to connect to the TeleDongle explicitly in
169 order for ao-view to be able to receive data.
171 Both RDF (radio direction finding) tones from the TeleMetrum and
172 GPS trekking data are available and together are very useful in
173 locating the rocket once it has landed. (The last good GPS data
174 received before touch-down will be on the data screen of 'ao-view'.)
176 Once you have recovered the rocket you can download the eeprom
177 contents using either 'ao-dumplog' (or possibly 'ao-eeprom'), over
178 either a USB cable or over the radio link using TeleDongle.
179 And by following the man page for 'ao-postflight' you can create
180 various data output reports, graphs, and even kml data to see the
181 flight trajectory in google-earth. (Moving the viewing angle making
182 sure to connect the yellow lines while in google-earth is the proper
185 As for ao-view.... some things are in the menu but don't do anything
186 very useful. The developers have stopped working on ao-view to focus
187 on a new, cross-platform ground station program. Mostly you just use
188 the Log and Device menus. It has a wonderful display of the incoming
189 flight data and I am sure you will enjoy what it has to say to you
190 once you enable the voice output!
191 </p><div class="section" title="FAQ"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2969939"></a>FAQ</h2></div></div></div><p>
192 The altimeter (TeleMetrum) seems to shut off when disconnected from the
193 computer. Make sure the battery is adequately charged. Remember the
194 unit will pull more power than the USB port can deliver before the
195 GPS enters "locked" mode. The battery charges best when TeleMetrum
198 It's impossible to stop the TeleDongle when it's in "p" mode, I have
199 to unplug the USB cable? Make sure you have tried to "escape out" of
200 this mode. If this doesn't work the reboot procedure for the
201 TeleDongle *is* to simply unplug it. 'cu' however will retain it's
202 outgoing buffer IF your "escape out" ('~~') does not work.
203 At this point using either 'ao-view' (or possibly
204 'cutemon') instead of 'cu' will 'clear' the issue and allow renewed
207 The amber LED (on the TeleMetrum/altimeter) lights up when both
208 battery and USB are connected. Does this mean it's charging?
209 Yes, the yellow LED indicates the charging at the 'regular' rate.
210 If the led is out but the unit is still plugged into a USB port,
211 then the battery is being charged at a 'trickle' rate.
213 There are no "dit-dah-dah-dit" sound like the manual mentions?
214 That's the "pad" mode. Weak batteries might be the problem.
215 It is also possible that the unit is horizontal and the output
216 is instead a "dit-dit" meaning 'idle'.
218 It's unclear how to use 'ao-view' and other programs when 'cu'
219 is running. You cannot have more than one program connected to
220 the TeleDongle at one time without apparent data loss as the
221 incoming data will not make it to both programs intact.
222 Disconnect whatever programs aren't currently being used.
224 How do I save flight data?
225 Live telemetry is written to file(s) whenever 'ao-view' is connected
226 to the TeleDongle. The file area defaults to ~/altos
227 but is easily changed using the menus in 'ao-view'. The files that
228 are written end in '.telem'. The after-flight
229 data-dumped files will end in .eeprom and represent continuous data
230 unlike the rf-linked .telem files that are subject to the
231 turnarounds/data-packaging time slots in the half-duplex rf data path.
232 See the above instructions on what and how to save the eeprom stored
233 data after physically retrieving your TeleMetrum.
234 </p></div></div><div class="chapter" title="Chapter 3. Specifications"><div class="titlepage"><div><div><h2 class="title"><a name="id2963754"></a>Chapter 3. Specifications</h2></div></div></div><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
235 Recording altimeter for model rocketry.
236 </p></li><li class="listitem"><p>
237 Supports dual deployment (can fire 2 ejection charges).
238 </p></li><li class="listitem"><p>
239 70cm ham-band transceiver for telemetry downlink.
240 </p></li><li class="listitem"><p>
241 Barometric pressure sensor good to 45k feet MSL.
242 </p></li><li class="listitem"><p>
243 1-axis high-g accelerometer for motor characterization, capable of
244 +/- 50g using default part.
245 </p></li><li class="listitem"><p>
246 On-board, integrated GPS receiver with 5hz update rate capability.
247 </p></li><li class="listitem"><p>
248 On-board 1 megabyte non-volatile memory for flight data storage.
249 </p></li><li class="listitem"><p>
250 USB interface for battery charging, configuration, and data recovery.
251 </p></li><li class="listitem"><p>
252 Fully integrated support for LiPo rechargeable batteries.
253 </p></li><li class="listitem"><p>
254 Uses LiPo to fire e-matches, support for optional separate pyro
256 </p></li><li class="listitem"><p>
257 2.75 x 1 inch board designed to fit inside 29mm airframe coupler tube.
258 </p></li></ul></div></div><div class="chapter" title="Chapter 4. Handling Precautions"><div class="titlepage"><div><div><h2 class="title"><a name="id2965995"></a>Chapter 4. Handling Precautions</h2></div></div></div><p>
259 TeleMetrum is a sophisticated electronic device. When handled gently and
260 properly installed in an airframe, it will deliver impressive results.
261 However, like all electronic devices, there are some precautions you
264 The Lithium Polymer rechargeable batteries used with TeleMetrum have an
265 extraordinary power density. This is great because we can fly with
266 much less battery mass than if we used alkaline batteries or previous
267 generation rechargeable batteries... but if they are punctured
268 or their leads are allowed to short, they can and will release their
270 Thus we recommend that you take some care when handling our batteries
271 and consider giving them some extra protection in your airframe. We
272 often wrap them in suitable scraps of closed-cell packing foam before
273 strapping them down, for example.
275 The TeleMetrum barometric sensor is sensitive to sunlight. In normal
276 mounting situations, it and all of the other surface mount components
277 are "down" towards whatever the underlying mounting surface is, so
278 this is not normally a problem. Please consider this, though, when
279 designing an installation, for example, in a 29mm airframe's see-through
282 The TeleMetrum barometric sensor sampling port must be able to "breathe",
283 both by not being covered by foam or tape or other materials that might
284 directly block the hole on the top of the sensor, but also by having a
285 suitable static vent to outside air.
287 As with all other rocketry electronics, TeleMetrum must be protected
288 from exposure to corrosive motor exhaust and ejection charge gasses.
289 </p></div><div class="chapter" title="Chapter 5. Hardware Overview"><div class="titlepage"><div><div><h2 class="title"><a name="id2979951"></a>Chapter 5. Hardware Overview</h2></div></div></div><p>
290 TeleMetrum is a 1 inch by 2.75 inch circuit board. It was designed to
291 fit inside coupler for 29mm airframe tubing, but using it in a tube that
292 small in diameter may require some creativity in mounting and wiring
293 to succeed! The default 1/4
294 wave UHF wire antenna attached to the center of the nose-cone end of
295 the board is about 7 inches long, and wiring for a power switch and
296 the e-matches for apogee and main ejection charges depart from the
297 fin can end of the board. Given all this, an ideal "simple" avionics
298 bay for TeleMetrum should have at least 10 inches of interior length.
300 A typical TeleMetrum installation using the on-board GPS antenna and
301 default wire UHF antenna involves attaching only a suitable
302 Lithium Polymer battery, a single pole switch for power on/off, and
303 two pairs of wires connecting e-matches for the apogee and main ejection
306 By default, we use the unregulated output of the LiPo battery directly
307 to fire ejection charges. This works marvelously with standard
308 low-current e-matches like the J-Tek from MJG Technologies, and with
309 Quest Q2G2 igniters. However, if you
310 want or need to use a separate pyro battery, you can do so by adding
311 a second 2mm connector to position B2 on the board and cutting the
312 thick pcb trace connecting the LiPo battery to the pyro circuit between
313 the two silk screen marks on the surface mount side of the board shown
316 We offer two choices of pyro and power switch connector, or you can
317 choose neither and solder wires directly to the board. All three choices
318 are reasonable depending on the constraints of your airframe. Our
319 favorite option when there is sufficient room above the board is to use
320 the Tyco pin header with polarization and locking. If you choose this
321 option, you crimp individual wires for the power switch and e-matches
322 into a mating connector, and installing and removing the TeleMetrum
323 board from an airframe is as easy as plugging or unplugging two
324 connectors. If the airframe will not support this much height or if
325 you want to be able to directly attach e-match leads to the board, we
326 offer a screw terminal block. This is very similar to what most other
327 altimeter vendors provide and so may be the most familiar
328 option. You'll need a very small straight blade screwdriver to connect
329 and disconnect the board in this case, such as you might find in a
330 jeweler's screwdriver set. Finally, you can forego both options and
331 solder wires directly to the board, which may be the best choice for
332 minimum diameter and/or minimum mass designs.
334 For most airframes, the integrated GPS antenna and wire UHF antenna are
335 a great combination. However, if you are installing in a carbon-fiber
336 electronics bay which is opaque to RF signals, you may need to use
337 off-board external antennas instead. In this case, you can order
338 TeleMetrum with an SMA connector for the UHF antenna connection, and
339 you can unplug the integrated GPS antenna and select an appropriate
340 off-board GPS antenna with cable terminating in a U.FL connector.
341 </p></div><div class="chapter" title="Chapter 6. Operation"><div class="titlepage"><div><div><h2 class="title"><a name="id2980270"></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="#id2966264">Firmware Modes </a></span></dt><dt><span class="section"><a href="#id2965911">GPS </a></span></dt><dt><span class="section"><a href="#id2977993">Ground Testing </a></span></dt><dt><span class="section"><a href="#id2962884">Radio Link </a></span></dt><dt><span class="section"><a href="#id2960257">Configurable Parameters</a></span></dt><dd><dl><dt><span class="section"><a href="#id2955134">Radio Channel</a></span></dt><dt><span class="section"><a href="#id2948360">Apogee Delay</a></span></dt><dt><span class="section"><a href="#id2982412">Main Deployment Altitude</a></span></dt></dl></dd><dt><span class="section"><a href="#id2969053">Calibration</a></span></dt><dd><dl><dt><span class="section"><a href="#id2969214">Radio Frequency</a></span></dt><dt><span class="section"><a href="#id2975078">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="id2966264"></a>Firmware Modes </h2></div></div></div><p>
342 The AltOS firmware build for TeleMetrum has two fundamental modes,
343 "idle" and "flight". Which of these modes the firmware operates in
344 is determined by the orientation of the rocket (well, actually the
345 board, of course...) at the time power is switched on. If the rocket
346 is "nose up", then TeleMetrum assumes it's on a rail or rod being
347 prepared for launch, so the firmware chooses flight mode. However,
348 if the rocket is more or less horizontal, the firmware instead enters
351 At power on, you will hear three beeps ("S" in Morse code for startup)
352 and then a pause while
353 TeleMetrum completes initialization and self tests, and decides which
356 In flight mode, TeleMetrum turns on the GPS system, engages the flight
357 state machine, goes into transmit-only mode on the RF link sending
358 telemetry, and waits for launch to be detected. Flight mode is
359 indicated by an audible "di-dah-dah-dit" ("P" for pad) on the
361 beeps indicating the state of the pyrotechnic igniter continuity.
362 One beep indicates apogee continuity, two beeps indicate
363 main continuity, three beeps indicate both apogee and main continuity,
364 and one longer "brap" sound indicates no continuity. For a dual
365 deploy flight, make sure you're getting three beeps before launching!
366 For apogee-only or motor eject flights, do what makes sense.
368 In idle mode, you will hear an audible "di-dit" ("I" for idle), and
369 the normal flight state machine is disengaged, thus
370 no ejection charges will fire. TeleMetrum also listens on the RF
371 link when in idle mode for packet mode requests sent from TeleDongle.
372 Commands can be issued to a TeleMetrum in idle mode over either
373 USB or the RF link equivalently.
374 Idle mode is useful for configuring TeleMetrum, for extracting data
375 from the on-board storage chip after flight, and for ground testing
378 One "neat trick" of particular value when TeleMetrum is used with very
379 large airframes, is that you can power the board up while the rocket
380 is horizontal, such that it comes up in idle mode. Then you can
381 raise the airframe to launch position, use a TeleDongle to open
382 a packet connection, and issue a 'reset' command which will cause
383 TeleMetrum to reboot, realize it's now nose-up, and thus choose
384 flight mode. This is much safer than standing on the top step of a
385 rickety step-ladder or hanging off the side of a launch tower with
386 a screw-driver trying to turn on your avionics before installing
388 </p></div><div class="section" title="GPS"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2965911"></a>GPS </h2></div></div></div><p>
389 TeleMetrum includes a complete GPS receiver. See a later section for
390 a brief explanation of how GPS works that will help you understand
391 the information in the telemetry stream. The bottom line is that
392 the TeleMetrum GPS receiver needs to lock onto at least four
393 satellites to obtain a solid 3 dimensional position fix and know
396 TeleMetrum provides backup power to the GPS chip any time a LiPo
397 battery is connected. This allows the receiver to "warm start" on
398 the launch rail much faster than if every power-on were a "cold start"
399 for the GPS receiver. In typical operations, powering up TeleMetrum
400 on the flight line in idle mode while performing final airframe
401 preparation will be sufficient to allow the GPS receiver to cold
402 start and acquire lock. Then the board can be powered down during
403 RSO review and installation on a launch rod or rail. When the board
404 is turned back on, the GPS system should lock very quickly, typically
405 long before igniter installation and return to the flight line are
407 </p></div><div class="section" title="Ground Testing"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2977993"></a>Ground Testing </h2></div></div></div><p>
408 An important aspect of preparing a rocket using electronic deployment
409 for flight is ground testing the recovery system. Thanks
410 to the bi-directional RF link central to the Altus Metrum system,
411 this can be accomplished in a TeleMetrum-equipped rocket without as
412 much work as you may be accustomed to with other systems. It can
415 Just prep the rocket for flight, then power up TeleMetrum while the
416 airframe is horizontal. This will cause the firmware to go into
417 "idle" mode, in which the normal flight state machine is disabled and
418 charges will not fire without manual command. Then, establish an
419 RF packet connection from a TeleDongle-equipped computer using the
420 P command from a safe distance. You can now command TeleMetrum to
421 fire the apogee or main charges to complete your testing.
423 In order to reduce the chance of accidental firing of pyrotechnic
424 charges, the command to fire a charge is intentionally somewhat
425 difficult to type, and the built-in help is slightly cryptic to
426 prevent accidental echoing of characters from the help text back at
427 the board from firing a charge. The command to fire the apogee
428 drogue charge is 'i DoIt drogue' and the command to fire the main
429 charge is 'i DoIt main'.
430 </p></div><div class="section" title="Radio Link"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2962884"></a>Radio Link </h2></div></div></div><p>
431 The chip our boards are based on incorporates an RF transceiver, but
432 it's not a full duplex system... each end can only be transmitting or
433 receiving at any given moment. So we had to decide how to manage the
436 By design, TeleMetrum firmware listens for an RF connection when
437 it's in "idle mode" (turned on while the rocket is horizontal), which
438 allows us to use the RF link to configure the rocket, do things like
439 ejection tests, and extract data after a flight without having to
440 crack open the airframe. However, when the board is in "flight
441 mode" (turned on when the rocket is vertical) the TeleMetrum only
442 transmits and doesn't listen at all. That's because we want to put
443 ultimate priority on event detection and getting telemetry out of
444 the rocket and out over
445 the RF link in case the rocket crashes and we aren't able to extract
448 We don't use a 'normal packet radio' mode because they're just too
449 inefficient. The GFSK modulation we use is just FSK with the
450 baseband pulses passed through a
451 Gaussian filter before they go into the modulator to limit the
452 transmitted bandwidth. When combined with the hardware forward error
453 correction support in the cc1111 chip, this allows us to have a very
454 robust 38.4 kilobit data link with only 10 milliwatts of transmit power,
455 a whip antenna in the rocket, and a hand-held Yagi on the ground. We've
456 had a test flight above 12k AGL with good reception, and calculations
457 suggest we should be good to 40k AGL or more with a 5-element yagi on
458 the ground. We hope to fly boards to higher altitudes soon, and would
459 of course appreciate customer feedback on performance in higher
461 </p></div><div class="section" title="Configurable Parameters"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2960257"></a>Configurable Parameters</h2></div></div></div><p>
462 Configuring a TeleMetrum board for flight is very simple. Because we
463 have both acceleration and pressure sensors, there is no need to set
464 a "mach delay", for example. The few configurable parameters can all
465 be set using a simple terminal program over the USB port or RF link
467 </p><div class="section" title="Radio Channel"><div class="titlepage"><div><div><h3 class="title"><a name="id2955134"></a>Radio Channel</h3></div></div></div><p>
468 Our firmware supports 10 channels. The default channel 0 corresponds
469 to a center frequency of 434.550 Mhz, and channels are spaced every
470 100 khz. Thus, channel 1 is 434.650 Mhz, and channel 9 is 435.550 Mhz.
471 At any given launch, we highly recommend coordinating who will use
472 each channel and when to avoid interference. And of course, both
473 TeleMetrum and TeleDongle must be configured to the same channel to
474 successfully communicate with each other.
476 To set the radio channel, use the 'c r' command, like 'c r 3' to set
478 As with all 'c' sub-commands, follow this with a 'c w' to write the
479 change to the parameter block in the on-board DataFlash chip.
480 </p></div><div class="section" title="Apogee Delay"><div class="titlepage"><div><div><h3 class="title"><a name="id2948360"></a>Apogee Delay</h3></div></div></div><p>
481 Apogee delay is the number of seconds after TeleMetrum detects flight
482 apogee that the drogue charge should be fired. In most cases, this
483 should be left at the default of 0. However, if you are flying
484 redundant electronics such as for an L3 certification, you may wish
485 to set one of your altimeters to a positive delay so that both
486 primary and backup pyrotechnic charges do not fire simultaneously.
488 To set the apogee delay, use the [FIXME] command.
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.
491 </p></div><div class="section" title="Main Deployment Altitude"><div class="titlepage"><div><div><h3 class="title"><a name="id2982412"></a>Main Deployment Altitude</h3></div></div></div><p>
492 By default, TeleMetrum will fire the main deployment charge at an
493 elevation of 250 meters (about 820 feet) above ground. We think this
494 is a good elevation for most airframes, but feel free to change this
495 to suit. In particular, if you are flying two altimeters, you may
497 deployment elevation for the backup altimeter to be something lower
498 than the primary so that both pyrotechnic charges don't fire
501 To set the main deployment altitude, use the [FIXME] command.
502 As with all 'c' sub-commands, follow this with a 'c w' to write the
503 change to the parameter block in the on-board DataFlash chip.
504 </p></div></div><div class="section" title="Calibration"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2969053"></a>Calibration</h2></div></div></div><p>
505 There are only two calibrations required for a TeleMetrum board, and
506 only one for TeleDongle.
507 </p><div class="section" title="Radio Frequency"><div class="titlepage"><div><div><h3 class="title"><a name="id2969214"></a>Radio Frequency</h3></div></div></div><p>
508 The radio frequency is synthesized from a clock based on the 48 Mhz
509 crystal on the board. The actual frequency of this oscillator must be
510 measured to generate a calibration constant. While our GFSK modulation
511 bandwidth is wide enough to allow boards to communicate even when
512 their oscillators are not on exactly the same frequency, performance
513 is best when they are closely matched.
514 Radio frequency calibration requires a calibrated frequency counter.
515 Fortunately, once set, the variation in frequency due to aging and
516 temperature changes is small enough that re-calibration by customers
517 should generally not be required.
519 To calibrate the radio frequency, connect the UHF antenna port to a
520 frequency counter, set the board to channel 0, and use the 'C'
521 command to generate a CW carrier. Wait for the transmitter temperature
522 to stabilize and the frequency to settle down.
523 Then, divide 434.550 Mhz by the
524 measured frequency and multiply by the current radio cal value show
525 in the 'c s' command. For an unprogrammed board, the default value
526 is 1186611. Take the resulting integer and program it using the 'c f'
527 command. Testing with the 'C' command again should show a carrier
528 within a few tens of Hertz of the intended frequency.
529 As with all 'c' sub-commands, follow this with a 'c w' to write the
530 change to the parameter block in the on-board DataFlash chip.
531 </p></div><div class="section" title="Accelerometer"><div class="titlepage"><div><div><h3 class="title"><a name="id2975078"></a>Accelerometer</h3></div></div></div><p>
532 The accelerometer we use has its own 5 volt power supply and
533 the output must be passed through a resistive voltage divider to match
534 the input of our 3.3 volt ADC. This means that unlike the barometric
535 sensor, the output of the acceleration sensor is not ratiometric to
536 the ADC converter, and calibration is required. We also support the
537 use of any of several accelerometers from a Freescale family that
538 includes at least +/- 40g, 50g, 100g, and 200g parts. Using gravity,
539 a simple 2-point calibration yields acceptable results capturing both
540 the different sensitivities and ranges of the different accelerometer
541 parts and any variation in power supply voltages or resistor values
542 in the divider network.
544 To calibrate the acceleration sensor, use the 'c a 0' command. You
545 will be prompted to orient the board vertically with the UHF antenna
546 up and press a key, then to orient the board vertically with the
547 UHF antenna down and press a key.
548 As with all 'c' sub-commands, follow this with a 'c w' to write the
549 change to the parameter block in the on-board DataFlash chip.
551 The +1g and -1g calibration points are included in each telemetry
552 frame and are part of the header extracted by ao-dumplog after flight.
553 Note that we always store and return raw ADC samples for each
554 sensor... nothing is permanently "lost" or "damaged" if the
556 </p></div></div></div><div class="chapter" title="Chapter 7. Using Altus Metrum Products"><div class="titlepage"><div><div><h2 class="title"><a name="id2976467"></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="#id2964669">Being Legal</a></span></dt><dd><dl><dt><span class="section"><a href="#id2969459">In the Rocket</a></span></dt><dt><span class="section"><a href="#id2964682">On the Ground</a></span></dt><dt><span class="section"><a href="#id2980718">Data Analysis</a></span></dt><dt><span class="section"><a href="#id2957709">Future Plans</a></span></dt></dl></dd><dt><span class="section"><a href="#id2961256">
558 </a></span></dt></dl></div><div class="section" title="Being Legal"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2964669"></a>Being Legal</h2></div></div></div><p>
559 First off, in the US, you need an [amateur radio license](../Radio) or
560 other authorization to legally operate the radio transmitters that are part
562 </p><div class="section" title="In the Rocket"><div class="titlepage"><div><div><h3 class="title"><a name="id2969459"></a>In the Rocket</h3></div></div></div><p>
563 In the rocket itself, you just need a [TeleMetrum](../TeleMetrum) board and
564 a LiPo rechargeable battery. An 860mAh battery weighs less than a 9V
565 alkaline battery, and will run a [TeleMetrum](../TeleMetrum) for hours.
567 By default, we ship TeleMetrum with a simple wire antenna. If your
568 electronics bay or the airframe it resides within is made of carbon fiber,
569 which is opaque to RF signals, you may choose to have an SMA connector
570 installed so that you can run a coaxial cable to an antenna mounted
571 elsewhere in the rocket.
572 </p></div><div class="section" title="On the Ground"><div class="titlepage"><div><div><h3 class="title"><a name="id2964682"></a>On the Ground</h3></div></div></div><p>
573 To receive the data stream from the rocket, you need an antenna and short
574 feedline connected to one of our [TeleDongle](../TeleDongle) units. The
575 TeleDongle in turn plugs directly into the USB port on a notebook
576 computer. Because TeleDongle looks like a simple serial port, your computer
577 does not require special device drivers... just plug it in.
579 Right now, all of our application software is written for Linux. However,
580 because we understand that many people run Windows or MacOS, we are working
581 on a new ground station program written in Java that should work on all
584 After the flight, you can use the RF link to extract the more detailed data
585 logged in the rocket, or you can use a mini USB cable to plug into the
586 TeleMetrum board directly. Pulling out the data without having to open up
587 the rocket is pretty cool! A USB cable is also how you charge the LiPo
588 battery, so you'll want one of those anyway... the same cable used by lots
589 of digital cameras and other modern electronic stuff will work fine.
591 If your rocket lands out of sight, you may enjoy having a hand-held GPS
592 receiver, so that you can put in a waypoint for the last reported rocket
593 position before touch-down. This makes looking for your rocket a lot like
594 Geo-Cacheing... just go to the waypoint and look around starting from there.
596 You may also enjoy having a ham radio "HT" that covers the 70cm band... you
597 can use that with your antenna to direction-find the rocket on the ground
598 the same way you can use a Walston or Beeline tracker. This can be handy
599 if the rocket is hiding in sage brush or a tree, or if the last GPS position
600 doesn't get you close enough because the rocket dropped into a canyon, or
601 the wind is blowing it across a dry lake bed, or something like that... Keith
602 and Bdale both currently own and use the Yaesu VX-7R at launches.
604 So, to recap, on the ground the hardware you'll need includes:
605 </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
606 an antenna and feedline
607 </li><li class="listitem">
609 </li><li class="listitem">
611 </li><li class="listitem">
612 optionally, a handheld GPS receiver
613 </li><li class="listitem">
614 optionally, an HT or receiver covering 435 Mhz
617 The best hand-held commercial directional antennas we've found for radio
618 direction finding rockets are from
619 <a class="ulink" href="http://www.arrowantennas.com/" target="_top">
622 The 440-3 and 440-5 are both good choices for finding a
623 TeleMetrum-equipped rocket when used with a suitable 70cm HT.
624 </p></div><div class="section" title="Data Analysis"><div class="titlepage"><div><div><h3 class="title"><a name="id2980718"></a>Data Analysis</h3></div></div></div><p>
625 Our software makes it easy to log the data from each flight, both the
626 telemetry received over the RF link during the flight itself, and the more
627 complete data log recorded in the DataFlash memory on the TeleMetrum
628 board. Once this data is on your computer, our postflight tools make it
629 easy to quickly get to the numbers everyone wants, like apogee altitude,
630 max acceleration, and max velocity. You can also generate and view a
631 standard set of plots showing the altitude, acceleration, and
632 velocity of the rocket during flight. And you can even export a data file
633 useable with Google Maps and Google Earth for visualizing the flight path
634 in two or three dimensions!
636 Our ultimate goal is to emit a set of files for each flight that can be
637 published as a web page per flight, or just viewed on your local disk with
639 </p></div><div class="section" title="Future Plans"><div class="titlepage"><div><div><h3 class="title"><a name="id2957709"></a>Future Plans</h3></div></div></div><p>
640 In the future, we intend to offer "companion boards" for the rocket that will
641 plug in to TeleMetrum to collect additional data, provide more pyro channels,
642 and so forth. A reference design for a companion board will be documented
643 soon, and will be compatible with open source Arduino programming tools.
645 We are also working on the design of a hand-held ground terminal that will
646 allow monitoring the rocket's status, collecting data during flight, and
647 logging data after flight without the need for a notebook computer on the
648 flight line. Particularly since it is so difficult to read most notebook
649 screens in direct sunlight, we think this will be a great thing to have.
651 Because all of our work is open, both the hardware designs and the software,
652 if you have some great idea for an addition to the current Altus Metrum family,
653 feel free to dive in and help! Or let us know what you'd like to see that
654 we aren't already working on, and maybe we'll get excited about it too...
655 </p></div></div><div class="section" title="How GPS Works"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2961256"></a>
657 </h2></div></div></div><p>
659 </p></div></div></div></body></html>
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