> For the complete documentation index, see [llms.txt](https://docs.holybro.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.holybro.com/pmw3901-optical-flow-sensor.md).
# PMW3901 Optical Flow Sensor
PMW3901 quick start guide
## Ardupilot Quick Start Guide
To enable the Holybro PMW3901 optical flow sensor in Ardupilot, set *FLOW\_TYPE* to 4 and *SERIALx\_PROTOCOL* to 18.
Telemetry 2 is used for this example
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.
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Optical flow test and calibration guide from Ardupilto WIKI
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## 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.
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.
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For more setup tips, visit PX4 official WIKI
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---
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