-<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>AltOS Companion Port</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="article"><div class="titlepage"><div><div><h2 class="title"><a name="idm6237008"></a>AltOS Companion Port</h2></div><div><h3 class="subtitle"><i>Protocol Definitions</i></h3></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 © 2012 Keith Packard</p></div><div><div class="legalnotice"><a name="idp47813408"></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 style="border-style:solid; width:100%;" summary="Revision History"><tr><th align="left" valign="top" colspan="2"><b>Revision History</b></th></tr><tr><td align="left">Revision 0.1</td><td align="left">13 January 2012</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 class="toc"><dt><span class="section"><a href="#idp47736896">1. Companion Port</a></span></dt><dt><span class="section"><a href="#idp47741392">2. Companion SPI Protocol</a></span></dt><dt><span class="section"><a href="#idp48671968">3. SPI Message Formats</a></span></dt><dd><dl><dt><span class="section"><a href="#idp48673216">3.1. Command Message</a></span></dt><dt><span class="section"><a href="#idp47752160">3.2. SETUP reply message</a></span></dt><dt><span class="section"><a href="#idp47773648">3.3. FETCH reply message</a></span></dt></dl></dd><dt><span class="section"><a href="#idp53319632">4. History and Motivation</a></span></dt></dl></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idp47736896"></a>1. Companion Port</h2></div></div></div><p>
- Many Altus Metrum products come with an eight pin Micro MaTch
- connector, called the Companion Port. This is often used to
- program devices using a programming cable. However, it can also
- be used to connect TeleMetrum to external companion boards
- (hence the name).
- </p><p>
- The Companion Port provides two different functions:
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
- Power. Both battery-level and 3.3V regulated power are
- available. Note that the amount of regulated power is not
- huge; TeleMetrum contains a 150mA regulator and uses, at
- peak, about 120mA or so. For applications needing more than
- a few dozen mA, placing a separate regulator on them and
- using the battery for power is probably a good idea.
- </p></li><li class="listitem"><p>
- SPI. The flight computer operates as a SPI master, using
- a protocol defined in this document. Companion boards
- provide a matching SPI slave implementation which supplies
- telemetry information for the radio downlink during flight
- </p></li></ul></div><p>
- </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idp47741392"></a>2. Companion SPI Protocol</h2></div></div></div><p>
- The flight computer implements a SPI master communications
- channel over the companion port, and uses this to get
- information about a connected companion board and then to get
- telemetry data for transmission during flight.
- </p><p>
- At startup time, the flight computer sends a setup request
- packet, and the companion board returns a board identifier, the
- desired telemetry update period and the number of data channels
- provided. The flight computer doesn't interpret the telemetry
- data at all, simply packing it up and sending it over the link.
- Telemetry packets are 32 bytes long, and companion packets use 8
- bytes as a header leaving room for a maximum of 12 16-bit data
- values.
- </p><p>
- Because of the limits of the AVR processors used in the first
- two companion boards, the SPI data rate is set to 187.5kbaud.
- </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idp48671968"></a>3. SPI Message Formats</h2></div></div></div><p>
- This section first defines the command message format sent from
- the flight computer to the companion board, and then the various
- reply message formats for each type of command message.
- </p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idp48673216"></a>3.1. Command Message</h3></div></div></div><div class="table"><a name="idp48673888"></a><p class="title"><b>Table 1. Companion Command Message</b></p><div class="table-contents"><table summary="Companion Command Message" border="1"><colgroup><col align="center" class="Offset"><col align="center" class="Data Type"><col align="left" class="Name"><col align="left" class="Description"></colgroup><thead><tr><th align="center">Offset</th><th align="center">Data Type</th><th align="center">Name</th><th align="center">Description</th></tr></thead><tbody><tr><td align="center">0</td><td align="center">uint8_t</td><td align="left">command</td><td align="left">Command identifier</td></tr><tr><td align="center">1</td><td align="center">uint8_t</td><td align="left">flight_state</td><td align="left">Current flight computer state</td></tr><tr><td align="center">2</td><td align="center">uint16_t</td><td align="left">tick</td><td align="left">Flight computer clock (100 ticks/second)</td></tr><tr><td align="center">4</td><td align="center">uint16_t</td><td align="left">serial</td><td align="left">Flight computer serial number</td></tr><tr><td align="center">6</td><td align="center">uint16_t</td><td align="left">flight</td><td align="left">Flight number</td></tr><tr><td align="center">8</td><td class="auto-generated"> </td><td class="auto-generated"> </td><td class="auto-generated"> </td></tr></tbody></table></div></div><br class="table-break"><div class="table"><a name="idp47917600"></a><p class="title"><b>Table 2. Companion Command Identifiers</b></p><div class="table-contents"><table summary="Companion Command Identifiers" border="1"><colgroup><col align="center" class="Value"><col align="left" class="Name"><col align="left" class="Description"></colgroup><thead><tr><th align="center">Value</th><th align="left">Name</th><th align="left">Description</th></tr></thead><tbody><tr><td align="center">1</td><td align="left">SETUP</td><td align="left">Supply the flight computer with companion
- information</td></tr><tr><td align="center">2</td><td align="left">FETCH</td><td align="left">Return telemetry information</td></tr><tr><td align="center">3</td><td align="left">NOTIFY</td><td align="left">Tell companion board when flight state
- changes</td></tr></tbody></table></div></div><br class="table-break"><p>
- The flight computer will send a SETUP message shortly after
- power-up and will then send FETCH messages no more often than
- the rate specified in the SETUP reply. NOTIFY messages will be
- sent whenever the flight state changes.
- </p><p>
- 'flight_state' records the current state of the flight,
- whether on the pad, under power, coasting to apogee or
- descending on the drogue or main chute.
- </p><p>
- 'tick' provides the current flight computer clock, which
- be used to synchronize data recorded on the flight computer
- with that recorded on the companion board in post-flight analysis.
- </p><p>
- 'serial' is the product serial number of the flight computer,
- 'flight' is the flight sequence number. Together, these two
- uniquely identify the flight and can be recorded with any
- companion board data logging to associate the companion data
- with the proper flight.
- </p><p>
- NOTIFY commands require no reply at all, they are used solely
- to inform the companion board when the state of the flight, as
- computed by the flight computer, changes. Companion boards can
- use this to change data collection parameters, disabling data
- logging until the flight starts and terminating it when the
- flight ends.
- </p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idp47752160"></a>3.2. SETUP reply message</h3></div></div></div><div class="table"><a name="idp47752832"></a><p class="title"><b>Table 3. SETUP reply contents</b></p><div class="table-contents"><table summary="SETUP reply contents" border="1"><colgroup><col align="center" class="Offset"><col align="center" class="Data Type"><col align="left" class="Name"><col align="left" class="Description"></colgroup><thead><tr><th align="center">Offset</th><th align="center">Data Type</th><th align="center">Name</th><th align="center">Description</th></tr></thead><tbody><tr><td align="center">0</td><td align="center">uint16_t</td><td align="left">board_id</td><td align="left">Board identifier</td></tr><tr><td align="center">2</td><td align="center">uint16_t</td><td align="left">board_id_inverse</td><td align="left">~board_id—used to tell if a board is present</td></tr><tr><td align="center">4</td><td align="center">uint8_t</td><td align="left">update_period</td><td align="left">Minimum time (in 100Hz ticks) between FETCH commands</td></tr><tr><td align="center">5</td><td align="center">uint8_t</td><td align="left">channels</td><td align="left">Number of data channels to retrieve in FETCH command</td></tr><tr><td align="center">6</td><td class="auto-generated"> </td><td class="auto-generated"> </td><td class="auto-generated"> </td></tr></tbody></table></div></div><br class="table-break"><p>
- The SETUP reply contains enough information to uniquely
- identify the companion board to the end user as well as for
- the flight computer to know how many data values to expect in
- reply to a FETCH command, and how often to fetch that data.
- </p><p>
- To detect the presence of a companion board, the flight
- computer checks to make sure that board_id_inverse is the
- bit-wise inverse of board_id. Current companion boards use
- USB product ID as the board_id, but the flight computer does
- not interpret this data and so it can be any value.
- </p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idp47773648"></a>3.3. FETCH reply message</h3></div></div></div><div class="table"><a name="idp47774320"></a><p class="title"><b>Table 4. FETCH reply contents</b></p><div class="table-contents"><table summary="FETCH reply contents" border="1"><colgroup><col align="center" class="Offset"><col align="center" class="Data Type"><col align="left" class="Name"><col align="left" class="Description"></colgroup><thead><tr><th align="center">Offset</th><th align="center">Data Type</th><th align="center">Name</th><th align="center">Description</th></tr></thead><tbody><tr><td align="center">0</td><td align="center">uint16_t</td><td align="left">data0</td><td align="left">0th data item</td></tr><tr><td align="center">2</td><td align="center">uint16_t</td><td align="left">data1</td><td align="left">1st data item</td></tr><tr><td align="center">...</td><td class="auto-generated"> </td><td class="auto-generated"> </td><td class="auto-generated"> </td></tr></tbody></table></div></div><br class="table-break"><p>
- The FETCH reply contains arbitrary data to be reported over
- the flight computer telemetry link. The number of 16-bit data items
- must match the 'channels' value provided in the SETUP reply
- message.
- </p></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idp53319632"></a>4. History and Motivation</h2></div></div></div><p>
- To allow cross-programming, the original TeleMetrum and
- TeleDongle designs needed to include some kind of
- connector. With that in place, adding the ability to connect
- external cards to TeleMetrum was fairly simple. We set the
- software piece of this puzzle aside until we had a companion
- board to use.
- </p><p>
- The first companion board was TeleScience. Designed to collect
- temperature data from the nose and fin of the airframe, the main
- requirement for the companion port was that it be able to report
- telemetry data during flight as a back-up in case the
- TeleScience on-board data was lost.
- </p><p>
- The second companion board, TelePyro, provides 8 additional
- channels for deployment, staging or other activities. To avoid
- re-programming the TeleMetrum to use TelePyro, we decided to
- provide enough information over the companion link for it to
- independently control those channels.
- </p><p>
- Providing a standard, constant interface between the flight
- computer and companion boards allows for the base flight
- computer firmware to include support for companion boards.
- </p></div></div></body></html>
+<!DOCTYPE html>
+<html lang="en">
+<head>
+<meta charset="UTF-8">
+<meta http-equiv="X-UA-Compatible" content="IE=edge">
+<meta name="viewport" content="width=device-width, initial-scale=1.0">
+<meta name="generator" content="Asciidoctor 2.0.10">
+<meta name="author" content="Keith Packard, Bdale Garbee">
+<meta name="copyright" content="Bdale Garbee and Keith Packard 2018">
+<title>AltOS Companion Port</title>
+<link rel="stylesheet" href="./am.css">
+</head>
+<body class="article">
+<div id="header">
+<h1>AltOS Companion Port</h1>
+<div class="details">
+<span id="author" class="author">Keith Packard</span><br>
+<span id="email" class="email"><a href="mailto:keithp@keithp.com">keithp@keithp.com</a></span><br>
+<span id="author2" class="author">Bdale Garbee</span><br>
+<span id="email2" class="email"><a href="mailto:bdale@gag.com">bdale@gag.com</a></span><br>
+<span id="revdate">15 Jun 2020</span>
+</div>
+<div id="toc" class="toc">
+<div id="toctitle">Table of Contents</div>
+<ul class="sectlevel1">
+<li><a href="#_license">License</a></li>
+<li><a href="#_companion_port">Companion Port</a></li>
+<li><a href="#_companion_spi_protocol">Companion SPI Protocol</a></li>
+<li><a href="#_spi_message_formats">SPI Message Formats</a>
+<ul class="sectlevel2">
+<li><a href="#_setup_reply_message">SETUP reply message</a></li>
+<li><a href="#_fetch_reply_message">FETCH reply message</a></li>
+</ul>
+</li>
+<li><a href="#_history_and_motivation">History and Motivation</a></li>
+</ul>
+</div>
+</div>
+<div id="content">
+<div id="preamble">
+<div class="sectionbody">
+<div id="logo" class="imageblock">
+<div class="content">
+<a class="image" href="https://altusmetrum.org"><img src="altusmetrum-oneline.svg" alt="Altus Metrum"></a>
+</div>
+</div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_license">License</h2>
+<div class="sectionbody">
+<div class="paragraph">
+<p>Copyright © 2018 Bdale Garbee and Keith Packard</p>
+</div>
+<div class="paragraph">
+<p>This document is released under the terms of the <a href="http://creativecommons.org/licenses/by-sa/3.0/">Creative Commons ShareAlike 3.0 License</a></p>
+</div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_companion_port">Companion Port</h2>
+<div class="sectionbody">
+<div class="paragraph">
+<p>Many Altus Metrum products come with an eight pin Micro MaTch
+connector, called the Companion Port. This is often used to
+program devices using a programming cable. However, it can
+also be used to connect TeleMetrum to external companion
+boards (hence the name).</p>
+</div>
+<div class="paragraph">
+<p>The Companion Port provides two different functions:</p>
+</div>
+<div class="ulist">
+<ul>
+<li>
+<p>Power. Both battery-level and 3.3V regulated power are
+available. Note that the amount of regulated power is not
+huge; TeleMetrum contains a 150mA regulator and uses, at
+peak, about 120mA or so. For applications needing more than
+a few dozen mA, placing a separate regulator on them and
+using the battery for power is probably a good idea.</p>
+</li>
+<li>
+<p>SPI. The flight computer operates as a SPI master, using
+a protocol defined in this document. Companion boards
+provide a matching SPI slave implementation which supplies
+telemetry information for the radio downlink during flight</p>
+</li>
+</ul>
+</div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_companion_spi_protocol">Companion SPI Protocol</h2>
+<div class="sectionbody">
+<div class="paragraph">
+<p>The flight computer implements a SPI master communications
+channel over the companion port, and uses this to get
+information about a connected companion board and then to get
+telemetry data for transmission during flight.</p>
+</div>
+<div class="paragraph">
+<p>At startup time, the flight computer sends a setup request
+packet, and the companion board returns a board identifier,
+the desired telemetry update period and the number of data
+channels provided. The flight computer doesn’t interpret the
+telemetry data at all, simply packing it up and sending it
+over the link. Telemetry packets are 32 bytes long, and
+companion packets use 8 bytes as a header leaving room for a
+maximum of 12 16-bit data values.</p>
+</div>
+<div class="paragraph">
+<p>Because of the limits of the AVR processors used in the first
+two companion boards, the SPI data rate is set to 187.5kbaud.</p>
+</div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_spi_message_formats">SPI Message Formats</h2>
+<div class="sectionbody">
+<div class="paragraph">
+<p>This section first defines the command message format sent from
+the flight computer to the companion board, and then the various
+reply message formats for each type of command message.</p>
+</div>
+<table class="tableblock frame-all grid-all stretch">
+<caption class="title">Table 1. Companion Command Message</caption>
+<colgroup>
+<col style="width: 6.25%;">
+<col style="width: 18.75%;">
+<col style="width: 18.75%;">
+<col style="width: 56.25%;">
+</colgroup>
+<tbody>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Offset</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Data Type</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Name</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Description</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">0</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">uint8_t</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">command</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Command identifier</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">1</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">uint8_t</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">flight_state</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Current flight computer state</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">2</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">uint16_t</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">tick</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Flight computer clock (100 ticks/second)</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">4</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">uint16_t</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">serial</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Flight computer serial number</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">6</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">uint16_t</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">flight</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Flight number</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">8</p></td>
+<td class="tableblock halign-left valign-top"></td>
+<td class="tableblock halign-left valign-top"></td>
+<td class="tableblock halign-left valign-top"></td>
+</tr>
+</tbody>
+</table>
+<table class="tableblock frame-all grid-all stretch">
+<caption class="title">Table 2. Companion Command Identifiers</caption>
+<colgroup>
+<col style="width: 7.6923%;">
+<col style="width: 23.0769%;">
+<col style="width: 69.2308%;">
+</colgroup>
+<tbody>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Value</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Name</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Description</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">1</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">SETUP</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Supply the flight computer with companion
+information</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">2</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">FETCH</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Return telemetry information</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">3</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">NOTIFY</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Tell companion board when flight state changes</p></td>
+</tr>
+</tbody>
+</table>
+<div class="paragraph">
+<p>The flight computer will send a SETUP message shortly after
+power-up and will then send FETCH messages no more often than
+the rate specified in the SETUP reply. NOTIFY messages will be
+sent whenever the flight state changes.</p>
+</div>
+<div class="paragraph">
+<p>'flight_state' records the current state of the flight,
+whether on the pad, under power, coasting to apogee or
+descending on the drogue or main chute.</p>
+</div>
+<div class="paragraph">
+<p>'tick' provides the current flight computer clock, which
+be used to synchronize data recorded on the flight computer
+with that recorded on the companion board in post-flight analysis.</p>
+</div>
+<div class="paragraph">
+<p>'serial' is the product serial number of the flight computer,
+'flight' is the flight sequence number. Together, these two
+uniquely identify the flight and can be recorded with any
+companion board data logging to associate the companion data
+with the proper flight.</p>
+</div>
+<div class="paragraph">
+<p>NOTIFY commands require no reply at all, they are used solely
+to inform the companion board when the state of the flight, as
+computed by the flight computer, changes. Companion boards can
+use this to change data collection parameters, disabling data
+logging until the flight starts and terminating it when the
+flight ends.</p>
+</div>
+<div class="sect2">
+<h3 id="_setup_reply_message">SETUP reply message</h3>
+<table class="tableblock frame-all grid-all stretch">
+<caption class="title">Table 3. SETUP reply contents</caption>
+<colgroup>
+<col style="width: 6.25%;">
+<col style="width: 18.75%;">
+<col style="width: 18.75%;">
+<col style="width: 56.25%;">
+</colgroup>
+<tbody>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Offset</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Data Type</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Name</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Description</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">0</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">uint16_t</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">board_id</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Board identifier</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">2</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">uint16_t</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">board_id_inverse</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">~board_id—used to tell if a board is present</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">4</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">uint8_t</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">update_period</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Minimum time (in 100Hz ticks) between FETCH commands</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">5</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">uint8_t</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">channels</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Number of data channels to retrieve in FETCH command</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">6</p></td>
+<td class="tableblock halign-left valign-top"></td>
+<td class="tableblock halign-left valign-top"></td>
+<td class="tableblock halign-left valign-top"></td>
+</tr>
+</tbody>
+</table>
+<div class="paragraph">
+<p>The SETUP reply contains enough information to uniquely
+identify the companion board to the end user as well as for
+the flight computer to know how many data values to expect in
+reply to a FETCH command, and how often to fetch that data.</p>
+</div>
+<div class="paragraph">
+<p>To detect the presence of a companion board, the flight
+computer checks to make sure that board_id_inverse is the
+bit-wise inverse of board_id. Current companion boards use
+USB product ID as the board_id, but the flight computer does
+not interpret this data and so it can be any value.</p>
+</div>
+</div>
+<div class="sect2">
+<h3 id="_fetch_reply_message">FETCH reply message</h3>
+<table class="tableblock frame-all grid-all stretch">
+<caption class="title">Table 4. FETCH reply contents</caption>
+<colgroup>
+<col style="width: 6.25%;">
+<col style="width: 18.75%;">
+<col style="width: 18.75%;">
+<col style="width: 56.25%;">
+</colgroup>
+<tbody>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Offset</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Data Type</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Name</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Description</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">0</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">uint16_t</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">data0</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">0th data item</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">2</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">uint16_t</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">data1</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">1st data item</p></td>
+</tr>
+<tr>
+<td class="tableblock halign-left valign-top"><p class="tableblock">…​</p></td>
+<td class="tableblock halign-left valign-top"></td>
+<td class="tableblock halign-left valign-top"></td>
+<td class="tableblock halign-left valign-top"></td>
+</tr>
+</tbody>
+</table>
+<div class="paragraph">
+<p>The FETCH reply contains arbitrary data to be reported
+over the flight computer telemetry link. The number of
+16-bit data items must match the 'channels' value
+provided in the SETUP reply message.</p>
+</div>
+</div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_history_and_motivation">History and Motivation</h2>
+<div class="sectionbody">
+<div class="paragraph">
+<p>To allow cross-programming, the original TeleMetrum and
+TeleDongle designs needed to include some kind of
+connector. With that in place, adding the ability to connect
+external cards to TeleMetrum was fairly simple. We set the
+software piece of this puzzle aside until we had a companion
+board to use.</p>
+</div>
+<div class="paragraph">
+<p>The first companion board was TeleScience. Designed to collect
+temperature data from the nose and fin of the airframe, the main
+requirement for the companion port was that it be able to report
+telemetry data during flight as a back-up in case the
+TeleScience on-board data was lost.</p>
+</div>
+<div class="paragraph">
+<p>The second companion board, TelePyro, provides 8 additional
+channels for deployment, staging or other activities. To avoid
+re-programming the TeleMetrum to use TelePyro, we decided to
+provide enough information over the companion link for it to
+independently control those channels.</p>
+</div>
+<div class="paragraph">
+<p>Providing a standard, constant interface between the flight
+computer and companion boards allows for the base flight
+computer firmware to include support for companion boards.</p>
+</div>
+</div>
+</div>
+</div>
+<div id="footer">
+<div id="footer-text">
+Last updated 2020-06-15 20:50:29 -0600
+</div>
+</div>
+</body>
+</html>
\ No newline at end of file
projects / web / altusmetrum / blobdiff