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<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>0.2</revnumber>
        <date>18 July 2010</date>
        <revremark>Significant update</revremark>
      </revision>
      <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>
    <para>
      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.
    </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 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). 
    </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 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, 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.
    </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.  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!
    </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.  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.
        </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 with a 
	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 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.
        </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 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!
        </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 on
	your TeleMetrum board if you want the change to stay in place across reboots.
          </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>
          <para>
	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.
          </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>