> For the complete documentation index, see [llms.txt](https://docs.ceruleansonar.com/c/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.ceruleansonar.com/c/rov-locator/communicating-with-the-rovl/messages-from-host-to-rovl/valid-commands-from-host-to-rovl.md).

# Valid Commands from Host to ROVL

<table data-header-hidden><thead><tr><th width="142"></th><th width="150"></th><th width="85"></th><th width="106"></th><th width="128"></th><th></th></tr></thead><tbody><tr><td><strong>Command</strong></td><td><strong>Description</strong></td><td><strong>Sticky</strong></td><td><strong>Mk II Receiver</strong></td><td><strong>Mk III Transceiver</strong></td><td><strong>Transmitter Transponder</strong></td></tr><tr><td><p>?</p><p>?*</p></td><td>Print configuration and menu of user commands</td><td> </td><td>X</td><td>X</td><td>Mk II / Mk III</td></tr><tr><td>A</td><td>Obsolete</td><td> </td><td></td><td> </td><td></td></tr><tr><td>!</td><td>Obsolete</td><td> </td><td></td><td> </td><td></td></tr><tr><td>BOOT</td><td>Reset CPU into bootload mode. We recommend you instead use the firmware loading capability of the CeruleanTracker application.</td><td></td><td>X</td><td>X</td><td>X</td></tr><tr><td>Dn</td><td>Obsolete</td><td> </td><td></td><td> </td><td> </td></tr><tr><td>E</td><td>Obsolete</td><td></td><td></td><td> </td><td> </td></tr><tr><td>IA, IB</td><td>Sets operating channel to A or B</td><td>X</td><td>X</td><td> </td><td>Mk II only</td></tr><tr><td>ID</td><td>Sets receiver to receive on both channels simultaneously (Dual Channel operation) (autosync versions only)</td><td>X</td><td>X</td><td> </td><td> </td></tr><tr><td>Jn</td><td>Set magnetic declination to n degrees</td><td>X</td><td>X</td><td>X</td><td> </td></tr><tr><td>K</td><td>Send the flash contents to the console</td><td></td><td>X</td><td>X</td><td></td></tr><tr><td>LOFF</td><td>Obsolete</td><td></td><td></td><td></td><td></td></tr><tr><td>Ln</td><td>Obsolete</td><td></td><td></td><td></td><td></td></tr><tr><td>Lxxxx</td><td>Obsolete</td><td></td><td></td><td></td><td></td></tr><tr><td>Mn</td><td>Pause mode, n=1 paused, n=0 resumed</td><td></td><td>X</td><td>X</td><td></td></tr><tr><td>On, Off</td><td>Turn transmitter pinging on and off.</td><td> </td><td> </td><td> </td><td>Mk II / Mk III</td></tr><tr><td>T COMPASS T NDOF</td><td>Set IMU Mode Mk II IMU only. Only valid if CIMU is off.</td><td>X</td><td>X</td><td></td><td></td></tr><tr><td>V3</td><td>Retweet GPS NMEA messages, use V0 to turn off (autosync versions only)</td><td> </td><td>X</td><td> </td><td> </td></tr><tr><td>W</td><td>Obsolete</td><td> </td><td></td><td> </td><td></td></tr><tr><td>X</td><td>Obsolete</td><td> </td><td></td><td> </td><td> </td></tr><tr><td>Y</td><td>Invalidate stored IMU calibration data and then save it next time it is valid (only valid if CIMU is off)</td><td>X</td><td>X</td><td></td><td> </td></tr><tr><td>YZ</td><td>Invalidate stored IMU calibration data and then save it next time it is valid (only valid if CIMU is off)</td><td>X</td><td>X</td><td></td><td></td></tr><tr><td>YCIMU ON</td><td>Enable Cerulean IMU (CIMU)</td><td>X</td><td></td><td>X</td><td></td></tr><tr><td>YCIMU OFF</td><td>Enable Mk II IMU</td><td>X</td><td>X</td><td></td><td></td></tr><tr><td>YACC x,y,z</td><td>Set CIMU accelerometer offsets to x,y,z</td><td>X</td><td></td><td>X</td><td></td></tr><tr><td>YGYR x,y,z</td><td>Set CIMU gyro offsets to x,y,z</td><td>X</td><td></td><td>X</td><td></td></tr><tr><td>YMAG x,y,z</td><td>Set CIMU magnetometer offsets to x,y,z</td><td>X</td><td></td><td>X</td><td></td></tr><tr><td>Zn</td><td>Set speed of sound to n meters/second</td><td>X</td><td>X</td><td><strong>X</strong></td><td> </td></tr><tr><td>$xxxxx,</td><td>NMEA command carrier </td><td> </td><td>X</td><td><strong>X</strong></td><td> </td></tr><tr><td>---</td><td><p>Mk III only, pass thru to co-processor </p><p></p></td><td></td><td></td><td>X</td><td>X</td></tr><tr><td>===</td><td>Mk III only, pass thru to co-processor (using ST bootloader serial parameters)</td><td></td><td></td><td>X</td><td>X</td></tr><tr><td>+++</td><td>Mk III only, end pass-thru mode</td><td></td><td></td><td>X</td><td>X</td></tr><tr><td>###</td><td>Reboot immediately</td><td></td><td>X</td><td>X</td><td>X</td></tr><tr><td>@n </td><td>Set Mk II / Mk III flag. <strong>Do not test this to see what happens!</strong>  It would be very sad if you accidentally bricked your device.</td><td>X</td><td>X</td><td>X</td><td>X</td></tr></tbody></table>

&#x20;

{% hint style="info" %}
Send these commands directly to the receiver or transmitter.
{% endhint %}

{% hint style="info" %}
Send newline (linefeed) (ASCII 0x0A) after all commands to make them take effect.
{% endhint %}

{% hint style="info" %}
Sending messages not listed may have unpleasant consequences including bricking your unit.
{% endhint %}

{% hint style="info" %}
These commands should not be sent in NMEA sentence format except as noted.
{% endhint %}