# PMW3901 Optical Flow Sensor

## Ardupilot Quick Start Guide

To enable the Holybro PMW3901 optical flow sensor in Ardupilot, set *FLOW\_TYPE* to 4 and *SERIALx\_PROTOCOL* to 18.

<figure><img src="https://2367252986-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FLIgtGDAvVGkCKGOJb1bR%2Fuploads%2FltimhfeSe9sRo199RWQl%2Fimage.png?alt=media&#x26;token=7a5d7d5d-4654-424a-9dcc-42f1e6248022" alt=""><figcaption></figcaption></figure>

<figure><img src="https://2367252986-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FLIgtGDAvVGkCKGOJb1bR%2Fuploads%2FXc4jsWy5fRERip10IZjS%2Fimage.png?alt=media&#x26;token=424b0c19-32e8-45f5-abde-e3a88fc9111e" alt=""><figcaption><p>Telemetry 2 is used for this example</p></figcaption></figure>

If you are not sure which serial port you are using, here is a list of serial mapping for the Pixhawk 6 family:

* SERIAL1 -> UART7 (Telem1)
* SERIAL2 -> UART5 (Telem2)
* SERIAL3 -> USART1 (GPS1)
* SERIAL4 -> UART8 (GPS2)
* SERIAL5 -> USART2 (Telem3) (not included on 6C Mini)

Once the sensor is correctly configured, check the *opt* related values from the status tab. If the values are non-zero while moving the sensor around, you are good to go.

<figure><img src="https://2367252986-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FLIgtGDAvVGkCKGOJb1bR%2Fuploads%2Fe8hRwiSBwgAeKQeEbEdt%2Fimage.png?alt=media&#x26;token=32d7dc40-31a9-40c3-b440-26e55af4b579" alt=""><figcaption></figcaption></figure>

{% embed url="<https://ardupilot.org/copter/docs/common-optical-flow-sensor-setup.html>" %}
Optical flow test and calibration guide from Ardupilto WIKI
{% endembed %}

## PX4 Quick Start Guide

To enable the Holybro PMW3901 optical flow sensor in PX4, simply set *SENS\_EN\_PMW3901* to enable, and the *SENS\_TFLOW\_CFG* to the corresponding port that sensor is connected to.

To save the settings, reboot or power cycle the flight controller.

<div align="left"><figure><img src="https://2367252986-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FLIgtGDAvVGkCKGOJb1bR%2Fuploads%2FlVDYMcd76qx7SHGZkHyL%2Fimage.png?alt=media&#x26;token=4d7ed8f5-f4a0-487b-b540-deefa20b0841" alt="" width="375"><figcaption></figcaption></figure> <figure><img src="https://2367252986-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FLIgtGDAvVGkCKGOJb1bR%2Fuploads%2FSD6TTAoWayUH8cM9zFeB%2Fimage.png?alt=media&#x26;token=053233c7-a468-4fb4-a4eb-6e260c43e974" alt="" width="563"><figcaption></figcaption></figure></div>

Once the sensor is correctly configured, you can head to MAVLink Inspector->OPTICAL\_FLOW\_RAD section to check the sensor reading to make sure the sensor is operational.

<figure><img src="https://2367252986-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FLIgtGDAvVGkCKGOJb1bR%2Fuploads%2FFiODSDglpzwq0ugZtZcg%2Fimage.png?alt=media&#x26;token=df94f95a-f2b2-427a-8fba-0215089dea64" alt=""><figcaption></figcaption></figure>

{% embed url="<https://docs.px4.io/main/en/sensor/optical_flow.html>" %}
For more setup tips, visit PX4 official WIKI
{% endembed %}


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