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-<?xml version="1.0" encoding="utf-8" ?>
-<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
- "/usr/share/xml/docbook/schema/dtd/4.5/docbookx.dtd">
-<book>
- <title>TeleMetrum</title>
- <subtitle>Owner's Manual for the TeleMetrum System</subtitle>
- <bookinfo>
- <author>
- <firstname>Bdale</firstname>
- <surname>Garbee</surname>
- </author>
- <author>
- <firstname>Keith</firstname>
- <surname>Packard</surname>
- </author>
- <copyright>
- <year>2010</year>
- <holder>Bdale Garbee and Keith Packard</holder>
- </copyright>
- <legalnotice>
- <para>
- This document is released under the terms of the
- <ulink url="http://creativecommons.org/licenses/by-sa/3.0/">
- Creative Commons ShareAlike 3.0
- </ulink>
- license.
- </para>
- </legalnotice>
- <revhistory>
- <revision>
- <revnumber>0.1</revnumber>
- <date>30 March 2010</date>
- <revremark>Initial content</revremark>
- </revision>
- </revhistory>
- </bookinfo>
- <chapter>
- <title>Introduction and Overview</title>
- <para>
- 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!
- </para>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- </chapter>
- <chapter>
- <title>Getting Started</title>
- <para>
- 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!
- </para>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- When you have successfully installed the software suite (either from
- compiled source code or as the pre-built Debian package) you will
- have 10 executable programs all of which have names beginning with 'ao-'.
- ('ao-view' is the lone GUI-based program.
- The rest are command-line based.) You will also
- have 10 man pages, that give you basic info on each program.
- And you will also get this documentation in two file types,
- telemetrum.pdf and telemetrum.html.
- Finally you will have a couple of control files that allow the ao-view
- GUI-based program to appear in your menu of programs (under
- the 'Internet' category).
- </para>
- <para>
- 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 (I use konsole for this,) 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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, 'cu' (and possibly 'cutecom') For instance, try to send
- (type) a 'cr2' and verify the channel change by sending a 'cs'.
- Verify you can connect and disconnect from the units while in 'cu'
- by sending the escape-disconnect mentioned above.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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'.)
- </para>
- <para>
- 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.)
- </para>
- <para>
- 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. 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!
- </para>
- <section>
- <title>FAQ</title>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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'.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- </section>
- </chapter>
- <chapter>
- <title>Specifications</title>
- <itemizedlist>
- <listitem>
- <para>
- Recording altimeter for model rocketry.
- </para>
- </listitem>
- <listitem>
- <para>
- Supports dual deployment (can fire 2 ejection charges).
- </para>
- </listitem>
- <listitem>
- <para>
- 70cm ham-band transceiver for telemetry downlink.
- </para>
- </listitem>
- <listitem>
- <para>
- Barometric pressure sensor good to 45k feet MSL.
- </para>
- </listitem>
- <listitem>
- <para>
- 1-axis high-g accelerometer for motor characterization, capable of
- +/- 50g using default part.
- </para>
- </listitem>
- <listitem>
- <para>
- On-board, integrated GPS receiver with 5hz update rate capability.
- </para>
- </listitem>
- <listitem>
- <para>
- On-board 1 megabyte non-volatile memory for flight data storage.
- </para>
- </listitem>
- <listitem>
- <para>
- USB interface for battery charging, configuration, and data recovery.
- </para>
- </listitem>
- <listitem>
- <para>
- Fully integrated support for LiPo rechargeable batteries.
- </para>
- </listitem>
- <listitem>
- <para>
- Uses LiPo to fire e-matches, support for optional separate pyro
- battery if needed.
- </para>
- </listitem>
- <listitem>
- <para>
- 2.75 x 1 inch board designed to fit inside 29mm airframe coupler tube.
- </para>
- </listitem>
- </itemizedlist>
- </chapter>
- <chapter>
- <title>Handling Precautions</title>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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's see-through
- plastic payload bay.
- </para>
- <para>
- 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.
- </para>
- <para>
- As with all other rocketry electronics, TeleMetrum must be protected
- from exposure to corrosive motor exhaust and ejection charge gasses.
- </para>
- </chapter>
- <chapter>
- <title>Hardware Overview</title>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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]
- </para>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- </chapter>
- <chapter>
- <title>Operation</title>
- <section>
- <title>Firmware Modes </title>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- In flight 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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!
- </para>
- </section>
- <section>
- <title>GPS </title>
- <para>
- 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!
- </para>
- <para>
- 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.
- </para>
- </section>
- <section>
- <title>Ground Testing </title>
- <para>
- 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!
- </para>
- <para>
- 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.
- </para>
- <para>
- 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'.
- </para>
- </section>
- <section>
- <title>Radio Link </title>
- <para>
- 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.
- </para>
- <para>
- 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...
- </para>
- <para>
- 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 a test flight above 12k AGL with good reception, and calculations
- suggest we should be good to 40k AGL or more 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!
- </para>
- </section>
- <section>
- <title>Configurable Parameters</title>
- <para>
- 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.
- </para>
- <section>
- <title>Radio Channel</title>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- </section>
- <section>
- <title>Apogee Delay</title>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- </section>
- <section>
- <title>Main Deployment Altitude</title>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- </section>
- </section>
- <section>
- <title>Calibration</title>
- <para>
- There are only two calibrations required for a TeleMetrum board, and
- only one for TeleDongle.
- </para>
- <section>
- <title>Radio Frequency</title>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- </section>
- <section>
- <title>Accelerometer</title>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- </section>
- </section>
- </chapter>
- <chapter>
- <title>Using Altus Metrum Products</title>
- <section>
- <title>Being Legal</title>
- <para>
- 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.
- </para>
- <section>
- <title>In the Rocket</title>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- </section>
- <section>
- <title>On the Ground</title>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- So, to recap, on the ground the hardware you'll need includes:
- <orderedlist inheritnum='inherit' numeration='arabic'>
- <listitem>
- an antenna and feedline
- </listitem>
- <listitem>
- a TeleDongle
- </listitem>
- <listitem>
- a notebook computer
- </listitem>
- <listitem>
- optionally, a handheld GPS receiver
- </listitem>
- <listitem>
- optionally, an HT or receiver covering 435 Mhz
- </listitem>
- </orderedlist>
- </para>
- <para>
- The best hand-held commercial directional antennas we've found for radio
- direction finding rockets are from
- <ulink url="http://www.arrowantennas.com/" >
- Arrow Antennas.
- </ulink>
- The 440-3 and 440-5 are both good choices for finding a
- TeleMetrum-equipped rocket when used with a suitable 70cm HT.
- </para>
- </section>
- <section>
- <title>Data Analysis</title>
- <para>
- 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!
- </para>
- <para>
- 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.
- </para>
- </section>
- <section>
- <title>Future Plans</title>
- <para>
- 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.
- </para>
- <para>
- 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.
- </para>
- <para>
- 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...
- </para>
- </section>
- </section>
- <section>
- <title>
- How GPS Works
- </title>
- <para>
- Placeholder.
- </para>
- </section>
- </chapter>
- </book>
-
projects / fw / altos / blobdiff