This module integrates a high-precision low-power optical tracking sensor PMW3901 and a high-precision laser sensor VL53LXX (2m version uses VL53L0X, 4m version uses VL53L1X), PMW3901 Optical flow sensor is responsible for measuring horizontal movement, VL53LXX laser sensor is. This module integrates a high-precision low-power optical tracking sensor PMW3901 and a high-precision laser sensor VL53LXX (2m version uses VL53L0X, 4m version uses VL53L1X), PMW3901 Optical flow sensor is responsible for measuring horizontal movement, VL53LXX laser sensor is. Make sure Optical Flow lens to ground >2cm for opflow initialization while FC starting up. Maximum range of VL53L0X is 2m, Altitude hold 0~2m @ throttle 0~100% if VL53L0X is enabled. SERIALn_PROTOCOL = 32, “n” is serial number of UART in ArduPilot hwdef, not the FC UART number. On some flight. PMW3901 is an ultra-light and multifunctional low-power optical flow module. Powered by Teledyne e2v's proprietary image sensor technology, Optimom has been thoughtfully designed to ensure there is minimum development. Matek Optical Flow and Lidar 3901-L0X is an additional sensor for measuring height and movement. It can be used to determine speed when navigating without GNSS — in buildings, underground, or in any other GNSS-denied environment. The video below shows PX4 holding position using the Ark.