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<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="id2276207"></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="id2559812"></a><p>
This document is released under the terms of the
<a class="ulink" href="http://creativecommons.org/licenses/by-sa/3.0/" target="_top">
Creative Commons ShareAlike 3.0
</a>
license.
</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 0.3</td><td align="left">12 November 2010</td></tr><tr><td align="left" colspan="2">
Add instructions for re-flashing devices using AltosUI
</td></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="#id2555013">1. Introduction and Overview</a></span></dt><dt><span class="chapter"><a href="#id2540100">2. Getting Started</a></span></dt><dd><dl><dt><span class="section"><a href="#id2559795">FAQ</a></span></dt></dl></dd><dt><span class="chapter"><a href="#id2546901">3. Specifications</a></span></dt><dt><span class="chapter"><a href="#id2574755">4. Handling Precautions</a></span></dt><dt><span class="chapter"><a href="#id2547133">5. Hardware Overview</a></span></dt><dt><span class="chapter"><a href="#id2552998">6. Operation</a></span></dt><dd><dl><dt><span class="section"><a href="#id2556146">Firmware Modes </a></span></dt><dt><span class="section"><a href="#id2557858">GPS </a></span></dt><dt><span class="section"><a href="#id2572262">Ground Testing </a></span></dt><dt><span class="section"><a href="#id2572259">Radio Link </a></span></dt><dt><span class="section"><a href="#id2542980">Configurable Parameters</a></span></dt><dd><dl><dt><span class="section"><a href="#id2563251">Radio Channel</a></span></dt><dt><span class="section"><a href="#id2554165">Apogee Delay</a></span></dt><dt><span class="section"><a href="#id2571971">Main Deployment Altitude</a></span></dt></dl></dd><dt><span class="section"><a href="#id2550600">Calibration</a></span></dt><dd><dl><dt><span class="section"><a href="#id2574322">Radio Frequency</a></span></dt><dt><span class="section"><a href="#id2564433">Accelerometer</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#id2554553">7. Updating Device Firmware</a></span></dt><dd><dl><dt><span class="section"><a href="#id2569887">Updating TeleMetrum Firmware</a></span></dt><dt><span class="section"><a href="#id2552683">Updating TeleDongle Firmware</a></span></dt></dl></dd><dt><span class="chapter"><a href="#id2539483">8. Using Altus Metrum Products</a></span></dt><dd><dl><dt><span class="section"><a href="#id2558109">Being Legal</a></span></dt><dd><dl><dt><span class="section"><a href="#id2554650">In the Rocket</a></span></dt><dt><span class="section"><a href="#id2572268">On the Ground</a></span></dt><dt><span class="section"><a href="#id2569008">Data Analysis</a></span></dt><dt><span class="section"><a href="#id2563568">Future Plans</a></span></dt></dl></dd><dt><span class="section"><a href="#id2567979">
How GPS Works
</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="id2555013"></a>Chapter 1. Introduction and Overview</h2></div></div></div><p>
Welcome to the Altus Metrum community! Our circuits and software reflect
our passion for both hobby rocketry and Free Software. We hope their
capabilities and performance will delight you in every way, but by
releasing all of our hardware and software designs under open licenses,
we also hope to empower you to take as active a role in our collective
future as you wish!
</p><p>
The focal point of our community is TeleMetrum, a dual deploy altimeter
with fully integrated GPS and radio telemetry as standard features, and
a "companion interface" that will support optional capabilities in the
future.
</p><p>
Complementing TeleMetrum is TeleDongle, a USB to RF interface for
communicating with TeleMetrum. Combined with your choice of antenna and
notebook computer, TeleDongle and our associated user interface software
form a complete ground station capable of logging and displaying in-flight
telemetry, aiding rocket recovery, then processing and archiving flight
data for analysis and review.
</p><p>
More products will be added to the Altus Metrum family over time, and
we currently envision that this will be a single, comprehensive manual
for the entire product family.
</p></div><div class="chapter" title="Chapter 2. Getting Started"><div class="titlepage"><div><div><h2 class="title"><a name="id2540100"></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="#id2559795">FAQ</a></span></dt></dl></div><p>
This chapter began as "The Mere-Mortals Quick Start/Usage Guide to
the Altus Metrum Starter Kit" by Bob Finch, W9YA, NAR 12965, TRA 12350,
w9ya@amsat.org. Bob was one of our first customers for a production
TeleMetrum, and the enthusiasm that led to his contribution of this
section is immensely gratifying and highy appreciated!
</p><p>
The first thing to do after you check the inventory of parts in your
"starter kit" is to charge the battery by plugging it into the
corresponding socket of the TeleMetrum and then using the USB A to B
cable to plug the Telemetrum into your computer's USB socket. The
TeleMetrum circuitry will charge the battery whenever it is plugged
into the usb socket. The TeleMetrum's on-off switch does NOT control
the charging circuitry. When the GPS chip is initially searching for
satellites, the unit will pull more current than it can pull from the
usb port, so the battery must be plugged in order to get a good
satellite lock. Once GPS is locked the current consumption goes back
down enough to enable charging while
running. So it's a good idea to fully charge the battery as your
first item of business so there is no issue getting and maintaining
satellite lock. The yellow charge indicator led will go out when the
battery is nearly full and the charger goes to trickle charge.
</p><p>
The other active device in the starter kit is the half-duplex TeleDongle
rf link. If you plug it in to your computer it should "just work",
showing up as a serial port device. If you are using Linux and are
having problems, try moving to a fresher kernel (2.6.33 or newer), as
there were some ugly USB serial driver bugs in earlier versions.
</p><p>
Next you should obtain and install the AltOS utilities. The first
generation sofware was written for Linux only. New software is coming
soon that will also run on Windows and Mac. For now, we'll concentrate
on Linux. If you are using Debian, an 'altos' package already exists,
see http://altusmetrum.org/AltOS for details on how to install it.
User-contributed directions for building packages on ArchLinux may be
found in the contrib/arch-linux directory as PKGBUILD files.
Between the debian/rules file and the PKGBUILD files in
contrib, you should find enough information to learn how to build the
software for any other version of Linux.
</p><p>
When you have successfully installed the software suite (either from
compiled source code or as the pre-built Debian package) you will
have 10 or so executable programs all of which have names beginning
with 'ao-'.
('ao-view' is the lone GUI-based program, the rest are command-line
oriented.) You will also have man pages, that give you basic info
on each program.
You will also get this documentation in two file types in the doc/
directory, telemetrum-doc.pdf and telemetrum-doc.html.
Finally you will have a couple control files that allow the ao-view
GUI-based program to appear in your menu of programs (under
the 'Internet' category).
</p><p>
Both Telemetrum and TeleDongle can be directly communicated
with using USB ports. The first thing you should try after getting
both units plugged into to your computer's usb port(s) is to run
'ao-list' from a terminal-window to see what port-device-name each
device has been assigned by the operating system.
You will need this information to access the devices via their
respective on-board firmware and data using other command line
programs in the AltOS software suite.
</p><p>
To access the device's firmware for configuration you need a terminal
program such as you would use to talk to a modem. The software
authors prefer using the program 'cu' which comes from the UUCP package
on most Unix-like systems such as Linux. An example command line for
cu might be 'cu -l /dev/ttyACM0', substituting the correct number
indicated from running the
ao-list program. Another reasonable terminal program for Linux is
'cutecom'. The default 'escape'
character used by CU (i.e. the character you use to
issue commands to cu itself instead of sending the command as input
to the connected device) is a '~'. You will need this for use in
only two different ways during normal operations. First is to exit
the program by sending a '~.' which is called a 'escape-disconnect'
and allows you to close-out from 'cu'. The
second use will be outlined later.
</p><p>
Both TeleMetrum and TeleDongle share the concept of a two level
command set in their firmware.
The first layer has several single letter commands. Once
you are using 'cu' (or 'cutecom') sending (typing) a '?'
returns a full list of these
commands. The second level are configuration sub-commands accessed
using the 'c' command, for
instance typing 'c?' will give you this second level of commands
(all of which require the
letter 'c' to access). Please note that most configuration options
are stored only in DataFlash memory, and only TeleMetrum has this
memory to save the various values entered like the channel number
and your callsign when powered off. TeleDongle requires that you
set these each time you plug it in, which ao-view can help with.
</p><p>
Try setting these config ('c' or second level menu) values. A good
place to start is by setting your call sign. By default, the boards
use 'N0CALL' which is cute, but not exactly legal!
Spend a few minutes getting comfortable with the units, their
firmware, and 'cu' (or possibly 'cutecom').
For instance, try to send
(type) a 'c r 2' and verify the channel change by sending a 'c s'.
Verify you can connect and disconnect from the units while in your
terminal program by sending the escape-disconnect mentioned above.
</p><p>
Note that the 'reboot' command, which is very useful on TeleMetrum,
will likely just cause problems with the dongle. The *correct* way
to reset the dongle is just to unplug and re-plug it.
</p><p>
A fun thing to do at the launch site and something you can do while
learning how to use these units is to play with the rf-link access
of the TeleMetrum from the TeleDongle. Be aware that you *must* create
some physical separation between the devices, otherwise the link will
not function due to signal overload in the receivers in each device.
</p><p>
Now might be a good time to take a break and read the rest of this
manual, particularly about the two "modes" that the TeleMetrum
can be placed in and how the position of the TeleMetrum when booting
up will determine whether the unit is in "pad" or "idle" mode.
</p><p>
You can access a TeleMetrum in idle mode from the Teledongle's USB
connection using the rf link
by issuing a 'p' command to the TeleDongle. Practice connecting and
disconnecting ('~~' while using 'cu') from the TeleMetrum. If
you cannot escape out of the "p" command, (by using a '~~' when in
CU) then it is likely that your kernel has issues. Try a newer version.
</p><p>
Using this rf link allows you to configure the TeleMetrum, test
fire e-matches and igniters from the flight line, check pyro-match
continuity and so forth. You can leave the unit turned on while it
is in 'idle mode' and then place the
rocket vertically on the launch pad, walk away and then issue a
reboot command. The TeleMetrum will reboot and start sending data
having changed to the "pad" mode. If the TeleDongle is not receiving
this data, you can disconnect 'cu' from the Teledongle using the
procedures mentioned above and THEN connect to the TeleDongle from
inside 'ao-view'. If this doesn't work, disconnect from the
TeleDongle, unplug it, and try again after plugging it back in.
</p><p>
Eventually the GPS will find enough satellites, lock in on them,
and 'ao-view' will both auditorially announce and visually indicate
that GPS is ready.
Now you can launch knowing that you have a good data path and
good satellite lock for flight data and recovery. Remember
you MUST tell ao-view to connect to the TeleDongle explicitly in
order for ao-view to be able to receive data.
</p><p>
Both RDF (radio direction finding) tones from the TeleMetrum and
GPS trekking data are available and together are very useful in
locating the rocket once it has landed. (The last good GPS data
received before touch-down will be on the data screen of 'ao-view'.)
</p><p>
Once you have recovered the rocket you can download the eeprom
contents using either 'ao-dumplog' (or possibly 'ao-eeprom'), over
either a USB cable or over the radio link using TeleDongle.
And by following the man page for 'ao-postflight' you can create
various data output reports, graphs, and even kml data to see the
flight trajectory in google-earth. (Moving the viewing angle making
sure to connect the yellow lines while in google-earth is the proper
technique.)
</p><p>
As for ao-view.... some things are in the menu but don't do anything
very useful. The developers have stopped working on ao-view to focus
on a new, cross-platform ground station program. So ao-view may or
may not be updated in the future. Mostly you just use
the Log and Device menus. It has a wonderful display of the incoming
flight data and I am sure you will enjoy what it has to say to you
once you enable the voice output!
</p><div class="section" title="FAQ"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2559795"></a>FAQ</h2></div></div></div><p>
The altimeter (TeleMetrum) seems to shut off when disconnected from the
computer. Make sure the battery is adequately charged. Remember the
unit will pull more power than the USB port can deliver before the
GPS enters "locked" mode. The battery charges best when TeleMetrum
is turned off.
</p><p>
It's impossible to stop the TeleDongle when it's in "p" mode, I have
to unplug the USB cable? Make sure you have tried to "escape out" of
this mode. If this doesn't work the reboot procedure for the
TeleDongle *is* to simply unplug it. 'cu' however will retain it's
outgoing buffer IF your "escape out" ('~~') does not work.
At this point using either 'ao-view' (or possibly
'cutemon') instead of 'cu' will 'clear' the issue and allow renewed
communication.
</p><p>
The amber LED (on the TeleMetrum/altimeter) lights up when both
battery and USB are connected. Does this mean it's charging?
Yes, the yellow LED indicates the charging at the 'regular' rate.
If the led is out but the unit is still plugged into a USB port,
then the battery is being charged at a 'trickle' rate.
</p><p>
There are no "dit-dah-dah-dit" sound like the manual mentions?
That's the "pad" mode. Weak batteries might be the problem.
It is also possible that the unit is horizontal and the output
is instead a "dit-dit" meaning 'idle'.
</p><p>
It's unclear how to use 'ao-view' and other programs when 'cu'
is running. You cannot have more than one program connected to
the TeleDongle at one time without apparent data loss as the
incoming data will not make it to both programs intact.
Disconnect whatever programs aren't currently being used.
</p><p>
How do I save flight data?
Live telemetry is written to file(s) whenever 'ao-view' is connected
to the TeleDongle. The file area defaults to ~/altos
but is easily changed using the menus in 'ao-view'. The files that
are written end in '.telem'. The after-flight
data-dumped files will end in .eeprom and represent continuous data
unlike the rf-linked .telem files that are subject to the
turnarounds/data-packaging time slots in the half-duplex rf data path.
See the above instructions on what and how to save the eeprom stored
data after physically retrieving your TeleMetrum. Make sure to save
the on-board data after each flight, as the current firmware will
over-write any previous flight data during a new flight.
</p></div></div><div class="chapter" title="Chapter 3. Specifications"><div class="titlepage"><div><div><h2 class="title"><a name="id2546901"></a>Chapter 3. Specifications</h2></div></div></div><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
Recording altimeter for model rocketry.
</p></li><li class="listitem"><p>
Supports dual deployment (can fire 2 ejection charges).
</p></li><li class="listitem"><p>
70cm ham-band transceiver for telemetry downlink.
</p></li><li class="listitem"><p>
Barometric pressure sensor good to 45k feet MSL.
</p></li><li class="listitem"><p>
1-axis high-g accelerometer for motor characterization, capable of
+/- 50g using default part.
</p></li><li class="listitem"><p>
On-board, integrated GPS receiver with 5hz update rate capability.
</p></li><li class="listitem"><p>
On-board 1 megabyte non-volatile memory for flight data storage.
</p></li><li class="listitem"><p>
USB interface for battery charging, configuration, and data recovery.
</p></li><li class="listitem"><p>
Fully integrated support for LiPo rechargeable batteries.
</p></li><li class="listitem"><p>
Uses LiPo to fire e-matches, support for optional separate pyro
battery if needed.
</p></li><li class="listitem"><p>
2.75 x 1 inch board designed to fit inside 29mm airframe coupler tube.
</p></li></ul></div></div><div class="chapter" title="Chapter 4. Handling Precautions"><div class="titlepage"><div><div><h2 class="title"><a name="id2574755"></a>Chapter 4. Handling Precautions</h2></div></div></div><p>
TeleMetrum is a sophisticated electronic device. When handled gently and
properly installed in an airframe, it will deliver impressive results.
However, like all electronic devices, there are some precautions you
must take.
</p><p>
The Lithium Polymer rechargeable batteries used with TeleMetrum have an
extraordinary power density. This is great because we can fly with
much less battery mass than if we used alkaline batteries or previous
generation rechargeable batteries... but if they are punctured
or their leads are allowed to short, they can and will release their
energy very rapidly!
Thus we recommend that you take some care when handling our batteries
and consider giving them some extra protection in your airframe. We
often wrap them in suitable scraps of closed-cell packing foam before
strapping them down, for example.
</p><p>
The TeleMetrum barometric sensor is sensitive to sunlight. In normal
mounting situations, it and all of the other surface mount components
are "down" towards whatever the underlying mounting surface is, so
this is not normally a problem. Please consider this, though, when
designing an installation, for example, in a 29mm airframe with a
see-through plastic payload bay.
</p><p>
The TeleMetrum barometric sensor sampling port must be able to
"breathe",
both by not being covered by foam or tape or other materials that might
directly block the hole on the top of the sensor, but also by having a
suitable static vent to outside air.
</p><p>
As with all other rocketry electronics, TeleMetrum must be protected
from exposure to corrosive motor exhaust and ejection charge gasses.
</p></div><div class="chapter" title="Chapter 5. Hardware Overview"><div class="titlepage"><div><div><h2 class="title"><a name="id2547133"></a>Chapter 5. Hardware Overview</h2></div></div></div><p>
TeleMetrum is a 1 inch by 2.75 inch circuit board. It was designed to
fit inside coupler for 29mm airframe tubing, but using it in a tube that
small in diameter may require some creativity in mounting and wiring
to succeed! The default 1/4
wave UHF wire antenna attached to the center of the nose-cone end of
the board is about 7 inches long, and wiring for a power switch and
the e-matches for apogee and main ejection charges depart from the
fin can end of the board. Given all this, an ideal "simple" avionics
bay for TeleMetrum should have at least 10 inches of interior length.
</p><p>
A typical TeleMetrum installation using the on-board GPS antenna and
default wire UHF antenna involves attaching only a suitable
Lithium Polymer battery, a single pole switch for power on/off, and
two pairs of wires connecting e-matches for the apogee and main ejection
charges.
</p><p>
By default, we use the unregulated output of the LiPo battery directly
to fire ejection charges. This works marvelously with standard
low-current e-matches like the J-Tek from MJG Technologies, and with
Quest Q2G2 igniters. However, if you
want or need to use a separate pyro battery, you can do so by adding
a second 2mm connector to position B2 on the board and cutting the
thick pcb trace connecting the LiPo battery to the pyro circuit between
the two silk screen marks on the surface mount side of the board shown
here [insert photo]
</p><p>
We offer two choices of pyro and power switch connector, or you can
choose neither and solder wires directly to the board. All three choices
are reasonable depending on the constraints of your airframe. Our
favorite option when there is sufficient room above the board is to use
the Tyco pin header with polarization and locking. If you choose this
option, you crimp individual wires for the power switch and e-matches
into a mating connector, and installing and removing the TeleMetrum
board from an airframe is as easy as plugging or unplugging two
connectors. If the airframe will not support this much height or if
you want to be able to directly attach e-match leads to the board, we
offer a screw terminal block. This is very similar to what most other
altimeter vendors provide and so may be the most familiar option.
You'll need a very small straight blade screwdriver to connect
and disconnect the board in this case, such as you might find in a
jeweler's screwdriver set. Finally, you can forego both options and
solder wires directly to the board, which may be the best choice for
minimum diameter and/or minimum mass designs.
</p><p>
For most airframes, the integrated GPS antenna and wire UHF antenna are
a great combination. However, if you are installing in a carbon-fiber
electronics bay which is opaque to RF signals, you may need to use
off-board external antennas instead. In this case, you can order
TeleMetrum with an SMA connector for the UHF antenna connection, and
you can unplug the integrated GPS antenna and select an appropriate
off-board GPS antenna with cable terminating in a U.FL connector.
</p></div><div class="chapter" title="Chapter 6. Operation"><div class="titlepage"><div><div><h2 class="title"><a name="id2552998"></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="#id2556146">Firmware Modes </a></span></dt><dt><span class="section"><a href="#id2557858">GPS </a></span></dt><dt><span class="section"><a href="#id2572262">Ground Testing </a></span></dt><dt><span class="section"><a href="#id2572259">Radio Link </a></span></dt><dt><span class="section"><a href="#id2542980">Configurable Parameters</a></span></dt><dd><dl><dt><span class="section"><a href="#id2563251">Radio Channel</a></span></dt><dt><span class="section"><a href="#id2554165">Apogee Delay</a></span></dt><dt><span class="section"><a href="#id2571971">Main Deployment Altitude</a></span></dt></dl></dd><dt><span class="section"><a href="#id2550600">Calibration</a></span></dt><dd><dl><dt><span class="section"><a href="#id2574322">Radio Frequency</a></span></dt><dt><span class="section"><a href="#id2564433">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="id2556146"></a>Firmware Modes </h2></div></div></div><p>
The AltOS firmware build for TeleMetrum has two fundamental modes,
"idle" and "flight". Which of these modes the firmware operates in
is determined by the orientation of the rocket (well, actually the
board, of course...) at the time power is switched on. If the rocket
is "nose up", then TeleMetrum assumes it's on a rail or rod being
prepared for launch, so the firmware chooses flight mode. However,
if the rocket is more or less horizontal, the firmware instead enters
idle mode.
</p><p>
At power on, you will hear three beeps
("S" in Morse code for startup) and then a pause while
TeleMetrum completes initialization and self tests, and decides which
mode to enter next.
</p><p>
In flight or "pad" mode, TeleMetrum turns on the GPS system,
engages the flight
state machine, goes into transmit-only mode on the RF link sending
telemetry, and waits for launch to be detected. Flight mode is
indicated by an audible "di-dah-dah-dit" ("P" for pad) on the
beeper, followed by
beeps indicating the state of the pyrotechnic igniter continuity.
One beep indicates apogee continuity, two beeps indicate
main continuity, three beeps indicate both apogee and main continuity,
and one longer "brap" sound indicates no continuity. For a dual
deploy flight, make sure you're getting three beeps before launching!
For apogee-only or motor eject flights, do what makes sense.
</p><p>
In idle mode, you will hear an audible "di-dit" ("I" for idle), and
the normal flight state machine is disengaged, thus
no ejection charges will fire. TeleMetrum also listens on the RF
link when in idle mode for packet mode requests sent from TeleDongle.
Commands can be issued to a TeleMetrum in idle mode over either
USB or the RF link equivalently.
Idle mode is useful for configuring TeleMetrum, for extracting data
from the on-board storage chip after flight, and for ground testing
pyro charges.
</p><p>
One "neat trick" of particular value when TeleMetrum is used with very
large airframes, is that you can power the board up while the rocket
is horizontal, such that it comes up in idle mode. Then you can
raise the airframe to launch position, use a TeleDongle to open
a packet connection, and issue a 'reset' command which will cause
TeleMetrum to reboot, realize it's now nose-up, and thus choose
flight mode. This is much safer than standing on the top step of a
rickety step-ladder or hanging off the side of a launch tower with
a screw-driver trying to turn on your avionics before installing
igniters!
</p></div><div class="section" title="GPS"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2557858"></a>GPS </h2></div></div></div><p>
TeleMetrum includes a complete GPS receiver. See a later section for
a brief explanation of how GPS works that will help you understand
the information in the telemetry stream. The bottom line is that
the TeleMetrum GPS receiver needs to lock onto at least four
satellites to obtain a solid 3 dimensional position fix and know
what time it is!
</p><p>
TeleMetrum provides backup power to the GPS chip any time a LiPo
battery is connected. This allows the receiver to "warm start" on
the launch rail much faster than if every power-on were a "cold start"
for the GPS receiver. In typical operations, powering up TeleMetrum
on the flight line in idle mode while performing final airframe
preparation will be sufficient to allow the GPS receiver to cold
start and acquire lock. Then the board can be powered down during
RSO review and installation on a launch rod or rail. When the board
is turned back on, the GPS system should lock very quickly, typically
long before igniter installation and return to the flight line are
complete.
</p></div><div class="section" title="Ground Testing"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2572262"></a>Ground Testing </h2></div></div></div><p>
An important aspect of preparing a rocket using electronic deployment
for flight is ground testing the recovery system. Thanks
to the bi-directional RF link central to the Altus Metrum system,
this can be accomplished in a TeleMetrum-equipped rocket without as
much work as you may be accustomed to with other systems. It can
even be fun!
</p><p>
Just prep the rocket for flight, then power up TeleMetrum while the
airframe is horizontal. This will cause the firmware to go into
"idle" mode, in which the normal flight state machine is disabled and
charges will not fire without manual command. Then, establish an
RF packet connection from a TeleDongle-equipped computer using the
P command from a safe distance. You can now command TeleMetrum to
fire the apogee or main charges to complete your testing.
</p><p>
In order to reduce the chance of accidental firing of pyrotechnic
charges, the command to fire a charge is intentionally somewhat
difficult to type, and the built-in help is slightly cryptic to
prevent accidental echoing of characters from the help text back at
the board from firing a charge. The command to fire the apogee
drogue charge is 'i DoIt drogue' and the command to fire the main
charge is 'i DoIt main'.
</p></div><div class="section" title="Radio Link"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2572259"></a>Radio Link </h2></div></div></div><p>
The chip our boards are based on incorporates an RF transceiver, but
it's not a full duplex system... each end can only be transmitting or
receiving at any given moment. So we had to decide how to manage the
link.
</p><p>
By design, TeleMetrum firmware listens for an RF connection when
it's in "idle mode" (turned on while the rocket is horizontal), which
allows us to use the RF link to configure the rocket, do things like
ejection tests, and extract data after a flight without having to
crack open the airframe. However, when the board is in "flight
mode" (turned on when the rocket is vertical) the TeleMetrum only
transmits and doesn't listen at all. That's because we want to put
ultimate priority on event detection and getting telemetry out of
the rocket and out over
the RF link in case the rocket crashes and we aren't able to extract
data later...
</p><p>
We don't use a 'normal packet radio' mode because they're just too
inefficient. The GFSK modulation we use is just FSK with the
baseband pulses passed through a
Gaussian filter before they go into the modulator to limit the
transmitted bandwidth. When combined with the hardware forward error
correction support in the cc1111 chip, this allows us to have a very
robust 38.4 kilobit data link with only 10 milliwatts of transmit power,
a whip antenna in the rocket, and a hand-held Yagi on the ground. We've
had flights to above 21k feet AGL with good reception, and calculations
suggest we should be good to well over 40k feet AGL with a 5-element yagi on
the ground. We hope to fly boards to higher altitudes soon, and would
of course appreciate customer feedback on performance in higher
altitude flights!
</p></div><div class="section" title="Configurable Parameters"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2542980"></a>Configurable Parameters</h2></div></div></div><p>
Configuring a TeleMetrum board for flight is very simple. Because we
have both acceleration and pressure sensors, there is no need to set
a "mach delay", for example. The few configurable parameters can all
be set using a simple terminal program over the USB port or RF link
via TeleDongle.
</p><div class="section" title="Radio Channel"><div class="titlepage"><div><div><h3 class="title"><a name="id2563251"></a>Radio Channel</h3></div></div></div><p>
Our firmware supports 10 channels. The default channel 0 corresponds
to a center frequency of 434.550 Mhz, and channels are spaced every
100 khz. Thus, channel 1 is 434.650 Mhz, and channel 9 is 435.550 Mhz.
At any given launch, we highly recommend coordinating who will use
each channel and when to avoid interference. And of course, both
TeleMetrum and TeleDongle must be configured to the same channel to
successfully communicate with each other.
</p><p>
To set the radio channel, use the 'c r' command, like 'c r 3' to set
channel 3.
As with all 'c' sub-commands, follow this with a 'c w' to write the
change to the parameter block in the on-board DataFlash chip on
your TeleMetrum board if you want the change to stay in place across reboots.
</p></div><div class="section" title="Apogee Delay"><div class="titlepage"><div><div><h3 class="title"><a name="id2554165"></a>Apogee Delay</h3></div></div></div><p>
Apogee delay is the number of seconds after TeleMetrum detects flight
apogee that the drogue charge should be fired. In most cases, this
should be left at the default of 0. However, if you are flying
redundant electronics such as for an L3 certification, you may wish
to set one of your altimeters to a positive delay so that both
primary and backup pyrotechnic charges do not fire simultaneously.
</p><p>
To set the apogee delay, use the [FIXME] command.
As with all 'c' sub-commands, follow this with a 'c w' to write the
change to the parameter block in the on-board DataFlash chip.
</p><p>
Please note that the TeleMetrum apogee detection algorithm always
fires a fraction of a second *after* apogee. If you are also flying
an altimeter like the PerfectFlite MAWD, which only supports selecting
0 or 1 seconds of apogee delay, you may wish to set the MAWD to 0
seconds delay and set the TeleMetrum to fire your backup 2 or 3
seconds later to avoid any chance of both charges firing
simultaneously. We've flown several airframes this way quite happily,
including Keith's successful L3 cert.
</p></div><div class="section" title="Main Deployment Altitude"><div class="titlepage"><div><div><h3 class="title"><a name="id2571971"></a>Main Deployment Altitude</h3></div></div></div><p>
By default, TeleMetrum will fire the main deployment charge at an
elevation of 250 meters (about 820 feet) above ground. We think this
is a good elevation for most airframes, but feel free to change this
to suit. In particular, if you are flying two altimeters, you may
wish to set the
deployment elevation for the backup altimeter to be something lower
than the primary so that both pyrotechnic charges don't fire
simultaneously.
</p><p>
To set the main deployment altitude, use the [FIXME] command.
As with all 'c' sub-commands, follow this with a 'c w' to write the
change to the parameter block in the on-board DataFlash chip.
</p></div></div><div class="section" title="Calibration"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2550600"></a>Calibration</h2></div></div></div><p>
There are only two calibrations required for a TeleMetrum board, and
only one for TeleDongle.
</p><div class="section" title="Radio Frequency"><div class="titlepage"><div><div><h3 class="title"><a name="id2574322"></a>Radio Frequency</h3></div></div></div><p>
The radio frequency is synthesized from a clock based on the 48 Mhz
crystal on the board. The actual frequency of this oscillator must be
measured to generate a calibration constant. While our GFSK modulation
bandwidth is wide enough to allow boards to communicate even when
their oscillators are not on exactly the same frequency, performance
is best when they are closely matched.
Radio frequency calibration requires a calibrated frequency counter.
Fortunately, once set, the variation in frequency due to aging and
temperature changes is small enough that re-calibration by customers
should generally not be required.
</p><p>
To calibrate the radio frequency, connect the UHF antenna port to a
frequency counter, set the board to channel 0, and use the 'C'
command to generate a CW carrier. Wait for the transmitter temperature
to stabilize and the frequency to settle down.
Then, divide 434.550 Mhz by the
measured frequency and multiply by the current radio cal value show
in the 'c s' command. For an unprogrammed board, the default value
is 1186611. Take the resulting integer and program it using the 'c f'
command. Testing with the 'C' command again should show a carrier
within a few tens of Hertz of the intended frequency.
As with all 'c' sub-commands, follow this with a 'c w' to write the
change to the parameter block in the on-board DataFlash chip.
</p></div><div class="section" title="Accelerometer"><div class="titlepage"><div><div><h3 class="title"><a name="id2564433"></a>Accelerometer</h3></div></div></div><p>
The accelerometer we use has its own 5 volt power supply and
the output must be passed through a resistive voltage divider to match
the input of our 3.3 volt ADC. This means that unlike the barometric
sensor, the output of the acceleration sensor is not ratiometric to
the ADC converter, and calibration is required. We also support the
use of any of several accelerometers from a Freescale family that
includes at least +/- 40g, 50g, 100g, and 200g parts. Using gravity,
a simple 2-point calibration yields acceptable results capturing both
the different sensitivities and ranges of the different accelerometer
parts and any variation in power supply voltages or resistor values
in the divider network.
</p><p>
To calibrate the acceleration sensor, use the 'c a 0' command. You
will be prompted to orient the board vertically with the UHF antenna
up and press a key, then to orient the board vertically with the
UHF antenna down and press a key.
As with all 'c' sub-commands, follow this with a 'c w' to write the
change to the parameter block in the on-board DataFlash chip.
</p><p>
The +1g and -1g calibration points are included in each telemetry
frame and are part of the header extracted by ao-dumplog after flight.
Note that we always store and return raw ADC samples for each
sensor... nothing is permanently "lost" or "damaged" if the
calibration is poor.
</p></div></div></div><div class="chapter" title="Chapter 7. Updating Device Firmware"><div class="titlepage"><div><div><h2 class="title"><a name="id2554553"></a>Chapter 7. Updating Device Firmware</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#id2569887">Updating TeleMetrum Firmware</a></span></dt><dt><span class="section"><a href="#id2552683">Updating TeleDongle Firmware</a></span></dt></dl></div><p>
The big conceptual thing to realize is that you have to use a
TeleDongle as a programmer to update a TeleMetrum, and vice versa.
Due to limited memory resources in the cc1111, we don't support
programming either unit directly over USB.
</p><p>
You may wish to begin by ensuring you have current firmware images.
These are distributed as part of the AltOS software bundle that
also includes the AltosUI ground station program. Newer ground
station versions typically work fine with older firmware versions,
so you don't need to update your devices just to try out new
software features. You can always download the most recent
version from http://www.altusmetrum.org/AltOS/.
</p><p>
We recommend updating TeleMetrum first, before updating TeleDongle.
</p><div class="section" title="Updating TeleMetrum Firmware"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2569887"></a>Updating TeleMetrum Firmware</h2></div></div></div><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
Find the 'programming cable' that you got as part of the starter
kit, that has a red 8-pin MicroMaTch connector on one end and a
red 4-pin MicroMaTch connector on the other end.
</li><li class="listitem">
Take the 2 screws out of the TeleDongle case to get access
to the circuit board.
</li><li class="listitem">
Plug the 8-pin end of the programming cable to the
matching connector on the TeleDongle, and the 4-pin end to the
matching connector on the TeleMetrum.
</li><li class="listitem">
Attach a battery to the TeleMetrum board.
</li><li class="listitem">
Plug the TeleDongle into your computer's USB port, and power
up the TeleMetrum.
</li><li class="listitem">
Run AltosUI, and select 'Flash Image' from the File menu.
</li><li class="listitem">
Pick the TeleDongle device from the list, identifying it as the
programming device.
</li><li class="listitem">
Select the image you want put on the TeleMetrum, which should have a
name in the form telemetrum-v1.0-0.7.1.ihx. It should be visible
in the default directory, if not you may have to poke around
your system to find it.
</li><li class="listitem">
Make sure the configuration parameters are reasonable
looking. If the serial number and/or RF configuration
values aren't right, you'll need to change them.
</li><li class="listitem">
Hit the 'OK' button and the software should proceed to flash
the TeleMetrum with new firmware, showing a progress bar.
</li><li class="listitem">
Confirm that the TeleMetrum board seems to have updated ok, which you
can do by plugging in to it over USB and using a terminal program
to connect to the board and issue the 'v' command to check
the version, etc.
</li><li class="listitem">
If something goes wrong, give it another try.
</li></ol></div></div><div class="section" title="Updating TeleDongle Firmware"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2552683"></a>Updating TeleDongle Firmware</h2></div></div></div><p>
Updating TeleDongle's firmware is just like updating TeleMetrum
firmware, but you switch which board is the programmer and which
is the programming target.
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
Find the 'programming cable' that you got as part of the starter
kit, that has a red 8-pin MicroMaTch connector on one end and a
red 4-pin MicroMaTch connector on the other end.
</li><li class="listitem">
Find the USB cable that you got as part of the starter kit, and
plug the "mini" end in to the mating connector on TeleMetrum.
</li><li class="listitem">
Take the 2 screws out of the TeleDongle case to get access
to the circuit board.
</li><li class="listitem">
Plug the 8-pin end of the programming cable to the (latching)
matching connector on the TeleMetrum, and the 4-pin end to the
matching connector on the TeleDongle.
</li><li class="listitem">
Attach a battery to the TeleMetrum board.
</li><li class="listitem">
Plug both TeleMetrum and TeleDongle into your computer's USB
ports, and power up the TeleMetrum.
</li><li class="listitem">
Run AltosUI, and select 'Flash Image' from the File menu.
</li><li class="listitem">
Pick the TeleMongle device from the list, identifying it as the
programming device.
</li><li class="listitem">
Select the image you want put on the TeleDongle, which should have a
name in the form teledongle-v0.2-0.7.1.ihx. It should be visible
in the default directory, if not you may have to poke around
your system to find it.
</li><li class="listitem">
Make sure the configuration parameters are reasonable
looking. If the serial number and/or RF configuration
values aren't right, you'll need to change them. The TeleDongle
serial number is on the "bottom" of the circuit board, and can
usually be read through the translucent blue plastic case without
needing to remove the board from the case.
</li><li class="listitem">
Hit the 'OK' button and the software should proceed to flash
the TeleDongle with new firmware, showing a progress bar.
</li><li class="listitem">
Confirm that the TeleDongle board seems to have updated ok, which you
can do by plugging in to it over USB and using a terminal program
to connect to the board and issue the 'v' command to check
the version, etc. Once you're happy, remove the programming cable
and put the cover back on the TeleDongle.
</li><li class="listitem">
If something goes wrong, give it another try.
</li></ol></div><p>
Be careful removing the programming cable from the locking 8-pin
connector on TeleMetrum. You'll need a fingernail or perhaps a thin
screwdriver or knife blade to gently pry the locking ears out
slightly to extract the connector. We used a locking connector on
TeleMetrum to help ensure that the cabling to companion boards
used in a rocket don't ever come loose accidentally in flight.
</p></div></div><div class="chapter" title="Chapter 8. Using Altus Metrum Products"><div class="titlepage"><div><div><h2 class="title"><a name="id2539483"></a>Chapter 8. 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="#id2558109">Being Legal</a></span></dt><dd><dl><dt><span class="section"><a href="#id2554650">In the Rocket</a></span></dt><dt><span class="section"><a href="#id2572268">On the Ground</a></span></dt><dt><span class="section"><a href="#id2569008">Data Analysis</a></span></dt><dt><span class="section"><a href="#id2563568">Future Plans</a></span></dt></dl></dd><dt><span class="section"><a href="#id2567979">
How GPS Works
</a></span></dt></dl></div><div class="section" title="Being Legal"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2558109"></a>Being Legal</h2></div></div></div><p>
First off, in the US, you need an [amateur radio license](../Radio) or
other authorization to legally operate the radio transmitters that are part
of our products.
</p><div class="section" title="In the Rocket"><div class="titlepage"><div><div><h3 class="title"><a name="id2554650"></a>In the Rocket</h3></div></div></div><p>
In the rocket itself, you just need a [TeleMetrum](../TeleMetrum) board and
a LiPo rechargeable battery. An 860mAh battery weighs less than a 9V
alkaline battery, and will run a [TeleMetrum](../TeleMetrum) for hours.
</p><p>
By default, we ship TeleMetrum with a simple wire antenna. If your
electronics bay or the airframe it resides within is made of carbon fiber,
which is opaque to RF signals, you may choose to have an SMA connector
installed so that you can run a coaxial cable to an antenna mounted
elsewhere in the rocket.
</p></div><div class="section" title="On the Ground"><div class="titlepage"><div><div><h3 class="title"><a name="id2572268"></a>On the Ground</h3></div></div></div><p>
To receive the data stream from the rocket, you need an antenna and short
feedline connected to one of our [TeleDongle](../TeleDongle) units. The
TeleDongle in turn plugs directly into the USB port on a notebook
computer. Because TeleDongle looks like a simple serial port, your computer
does not require special device drivers... just plug it in.
</p><p>
Right now, all of our application software is written for Linux. However,
because we understand that many people run Windows or MacOS, we are working
on a new ground station program written in Java that should work on all
operating systems.
</p><p>
After the flight, you can use the RF link to extract the more detailed data
logged in the rocket, or you can use a mini USB cable to plug into the
TeleMetrum board directly. Pulling out the data without having to open up
the rocket is pretty cool! A USB cable is also how you charge the LiPo
battery, so you'll want one of those anyway... the same cable used by lots
of digital cameras and other modern electronic stuff will work fine.
</p><p>
If your rocket lands out of sight, you may enjoy having a hand-held GPS
receiver, so that you can put in a waypoint for the last reported rocket
position before touch-down. This makes looking for your rocket a lot like
Geo-Cacheing... just go to the waypoint and look around starting from there.
</p><p>
You may also enjoy having a ham radio "HT" that covers the 70cm band... you
can use that with your antenna to direction-find the rocket on the ground
the same way you can use a Walston or Beeline tracker. This can be handy
if the rocket is hiding in sage brush or a tree, or if the last GPS position
doesn't get you close enough because the rocket dropped into a canyon, or
the wind is blowing it across a dry lake bed, or something like that... Keith
and Bdale both currently own and use the Yaesu VX-7R at launches.
</p><p>
So, to recap, on the ground the hardware you'll need includes:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
an antenna and feedline
</li><li class="listitem">
a TeleDongle
</li><li class="listitem">
a notebook computer
</li><li class="listitem">
optionally, a handheld GPS receiver
</li><li class="listitem">
optionally, an HT or receiver covering 435 Mhz
</li></ol></div><p>
</p><p>
The best hand-held commercial directional antennas we've found for radio
direction finding rockets are from
<a class="ulink" href="http://www.arrowantennas.com/" target="_top">
Arrow Antennas.
</a>
The 440-3 and 440-5 are both good choices for finding a
TeleMetrum-equipped rocket when used with a suitable 70cm HT.
</p></div><div class="section" title="Data Analysis"><div class="titlepage"><div><div><h3 class="title"><a name="id2569008"></a>Data Analysis</h3></div></div></div><p>
Our software makes it easy to log the data from each flight, both the
telemetry received over the RF link during the flight itself, and the more
complete data log recorded in the DataFlash memory on the TeleMetrum
board. Once this data is on your computer, our postflight tools make it
easy to quickly get to the numbers everyone wants, like apogee altitude,
max acceleration, and max velocity. You can also generate and view a
standard set of plots showing the altitude, acceleration, and
velocity of the rocket during flight. And you can even export a data file
useable with Google Maps and Google Earth for visualizing the flight path
in two or three dimensions!
</p><p>
Our ultimate goal is to emit a set of files for each flight that can be
published as a web page per flight, or just viewed on your local disk with
a web browser.
</p></div><div class="section" title="Future Plans"><div class="titlepage"><div><div><h3 class="title"><a name="id2563568"></a>Future Plans</h3></div></div></div><p>
In the future, we intend to offer "companion boards" for the rocket that will
plug in to TeleMetrum to collect additional data, provide more pyro channels,
and so forth. A reference design for a companion board will be documented
soon, and will be compatible with open source Arduino programming tools.
</p><p>
We are also working on the design of a hand-held ground terminal that will
allow monitoring the rocket's status, collecting data during flight, and
logging data after flight without the need for a notebook computer on the
flight line. Particularly since it is so difficult to read most notebook
screens in direct sunlight, we think this will be a great thing to have.
</p><p>
Because all of our work is open, both the hardware designs and the software,
if you have some great idea for an addition to the current Altus Metrum family,
feel free to dive in and help! Or let us know what you'd like to see that
we aren't already working on, and maybe we'll get excited about it too...
</p></div></div><div class="section" title="How GPS Works"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2567979"></a>
How GPS Works
</h2></div></div></div><p>
Placeholder.
</p></div></div></div></body></html>
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