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diff --git a/AltOS/doc/companion.html b/AltOS/doc/companion.html index 7d90387..b9a684b 100644 --- a/AltOS/doc/companion.html +++ b/AltOS/doc/companion.html @@ -1,116 +1,79 @@ -<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="idm46040259592256"></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="idm46040233083952"></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="#idm46040232383776">1. Companion Port</a></span></dt><dt><span class="section"><a href="#idm46040232379280">2. Companion SPI Protocol</a></span></dt><dt><span class="section"><a href="#idm46040232376384">3. SPI Message Formats</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46040232375104">3.1. Command Message</a></span></dt><dt><span class="section"><a href="#idm46040233245360">3.2. SETUP reply message</a></span></dt><dt><span class="section"><a href="#idm46040233223824">3.3. FETCH reply message</a></span></dt></dl></dd><dt><span class="section"><a href="#idm46040227732240">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="idm46040232383776"></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="idm46040232379280"></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="idm46040232376384"></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="idm46040232375104"></a>3.1. Command Message</h3></div></div></div><div class="table"><a name="idm46040232374432"></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="idm46040233261392"></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="idm46040233245360"></a>3.2. SETUP reply message</h3></div></div></div><div class="table"><a name="idm46040233244688"></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="idm46040233223824"></a>3.3. FETCH reply message</h3></div></div></div><div class="table"><a name="idm46040227748144"></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="idm46040227732240"></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> +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>AltOS Companion Port</title><link rel="stylesheet" type="text/css" href="am.css" /><meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /></head><body><div xml:lang="en" class="article" lang="en"><div class="titlepage"><div><div><h2 class="title"><a id="idm1"></a>AltOS Companion Port</h2></div><div><h3 class="subtitle"><em>Protocol Definitions</em></h3></div><div><div class="author"><h3 class="author"><span class="firstname">Keith</span> <span class="surname">Packard</span></h3><code class="email"><<a class="email" href="mailto:keithp@keithp.com">keithp@keithp.com</a>></code></div></div><div><p class="copyright">Copyright © 2012 Keith Packard</p></div><div><div class="legalnotice"><a id="idm13"></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><a href="companion-revhistory.html">Revision History</a></div></div><hr /></div><div class="toc"><p><strong>Table of Contents</strong></p><dl class="toc"><dt><span class="section"><a href="#_companion_port">1. Companion Port</a></span></dt><dt><span class="section"><a href="#_companion_spi_protocol">2. Companion SPI Protocol</a></span></dt><dt><span class="section"><a href="#_spi_message_formats">3. SPI Message Formats</a></span></dt><dd><dl><dt><span class="section"><a href="#_setup_reply_message">3.1. SETUP reply message</a></span></dt><dt><span class="section"><a href="#_fetch_reply_message">3.2. FETCH reply message</a></span></dt></dl></dd><dt><span class="section"><a href="#_history_and_motivation">4. History and Motivation</a></span></dt></dl></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="_companion_port"></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"> +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. +</li><li class="listitem"> +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 +</li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="_companion_spi_protocol"></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 id="_spi_message_formats"></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="table"><a id="idm38"></a><p class="title"><strong>Table 1. Companion Command Message</strong></p><div class="table-contents"><table class="table" summary="Companion Command Message" cellpadding="4px" style="border-collapse: collapse;border-top: 1px solid #78079a; border-bottom: 1px solid #78079a; border-left: 1px solid #78079a; border-right: 1px solid #78079a; "><colgroup><col class="col_1" /><col class="col_2" /><col class="col_3" /><col class="col_4" /></colgroup><tbody><tr><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Offset</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Data Type</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Name</p></td><td style="border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Description</p></td></tr><tr><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>0</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>uint8_t</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>command</p></td><td style="border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Command identifier</p></td></tr><tr><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>1</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>uint8_t</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>flight_state</p></td><td style="border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Current flight computer state</p></td></tr><tr><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>2</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>uint16_t</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>tick</p></td><td style="border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Flight computer clock (100 ticks/second)</p></td></tr><tr><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>4</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>uint16_t</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>serial</p></td><td style="border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Flight computer serial number</p></td></tr><tr><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>6</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>uint16_t</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>flight</p></td><td style="border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Flight number</p></td></tr><tr><td style="border-right: 1px solid #78079a; " align="left" valign="top"><p>8</p></td><td style="border-right: 1px solid #78079a; " align="left" valign="top"><p></p></td><td style="border-right: 1px solid #78079a; " align="left" valign="top"><p></p></td><td style="" align="left" valign="top"><p></p></td></tr></tbody></table></div></div><br class="table-break" /><div class="table"><a id="idm109"></a><p class="title"><strong>Table 2. Companion Command Identifiers</strong></p><div class="table-contents"><table class="table" summary="Companion Command Identifiers" cellpadding="4px" style="border-collapse: collapse;border-top: 1px solid #78079a; border-bottom: 1px solid #78079a; border-left: 1px solid #78079a; border-right: 1px solid #78079a; "><colgroup><col class="col_1" /><col class="col_2" /><col class="col_3" /></colgroup><tbody><tr><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Value</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Name</p></td><td style="border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Description</p></td></tr><tr><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>1</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>SETUP</p></td><td style="border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Supply the flight computer with companion +information</p></td></tr><tr><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>2</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>FETCH</p></td><td style="border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Return telemetry information</p></td></tr><tr><td style="border-right: 1px solid #78079a; " align="left" valign="top"><p>3</p></td><td style="border-right: 1px solid #78079a; " align="left" valign="top"><p>NOTIFY</p></td><td style="" align="left" valign="top"><p>Tell companion board when flight state changes</p></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><span class="emphasis"><em>flight_state</em></span> 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><span class="emphasis"><em>tick</em></span> 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><span class="emphasis"><em>serial</em></span> is the product serial number of the flight computer, +<span class="emphasis"><em>flight</em></span> 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 class="section"><div class="titlepage"><div><div><h3 class="title"><a id="_setup_reply_message"></a>3.1. SETUP reply message</h3></div></div></div><div class="table"><a id="idm155"></a><p class="title"><strong>Table 3. SETUP reply contents</strong></p><div class="table-contents"><table class="table" summary="SETUP reply contents" cellpadding="4px" style="border-collapse: collapse;border-top: 1px solid #78079a; border-bottom: 1px solid #78079a; border-left: 1px solid #78079a; border-right: 1px solid #78079a; "><colgroup><col class="col_1" /><col class="col_2" /><col class="col_3" /><col class="col_4" /></colgroup><tbody><tr><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Offset</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Data Type</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Name</p></td><td style="border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Description</p></td></tr><tr><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>0</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>uint16_t</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>board_id</p></td><td style="border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Board identifier</p></td></tr><tr><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>2</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>uint16_t</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>board_id_inverse</p></td><td style="border-bottom: 1px solid #78079a; " align="left" valign="top"><p>~board_id—used to tell if a board is present</p></td></tr><tr><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>4</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>uint8_t</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>update_period</p></td><td style="border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Minimum time (in 100Hz ticks) between FETCH commands</p></td></tr><tr><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>5</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>uint8_t</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>channels</p></td><td style="border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Number of data channels to retrieve in FETCH command</p></td></tr><tr><td style="border-right: 1px solid #78079a; " align="left" valign="top"><p>6</p></td><td style="border-right: 1px solid #78079a; " align="left" valign="top"><p></p></td><td style="border-right: 1px solid #78079a; " align="left" valign="top"><p></p></td><td style="" align="left" valign="top"><p></p></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 id="_fetch_reply_message"></a>3.2. FETCH reply message</h3></div></div></div><div class="table"><a id="idm221"></a><p class="title"><strong>Table 4. FETCH reply contents</strong></p><div class="table-contents"><table class="table" summary="FETCH reply contents" cellpadding="4px" style="border-collapse: collapse;border-top: 1px solid #78079a; border-bottom: 1px solid #78079a; border-left: 1px solid #78079a; border-right: 1px solid #78079a; "><colgroup><col class="col_1" /><col class="col_2" /><col class="col_3" /><col class="col_4" /></colgroup><tbody><tr><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Offset</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Data Type</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Name</p></td><td style="border-bottom: 1px solid #78079a; " align="left" valign="top"><p>Description</p></td></tr><tr><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>0</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>uint16_t</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>data0</p></td><td style="border-bottom: 1px solid #78079a; " align="left" valign="top"><p>0th data item</p></td></tr><tr><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>2</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>uint16_t</p></td><td style="border-right: 1px solid #78079a; border-bottom: 1px solid #78079a; " align="left" valign="top"><p>data1</p></td><td style="border-bottom: 1px solid #78079a; " align="left" valign="top"><p>1st data item</p></td></tr><tr><td style="border-right: 1px solid #78079a; " align="left" valign="top"><p>…</p></td><td style="border-right: 1px solid #78079a; " align="left" valign="top"><p></p></td><td style="border-right: 1px solid #78079a; " align="left" valign="top"><p></p></td><td style="" align="left" valign="top"><p></p></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 <span class="emphasis"><em>channels</em></span> 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 id="_history_and_motivation"></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>
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