+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