PX4FLOW | Communication Protocol bt board/chip and Sonar

Hello guys,
Does anyone know whether the communication protocol between the px4flow board and the MB1043 sonar sensor is normal UART-TTL protocol (TX/RX) or not(only use RX pin)? The datasheet of MB1043 sensor shows that it could connect only RX pin with the chip, for instance here. And actually I would like to replace this sonar with a laser so as to be used far away from the ground.
Thx!
Ze

I get it!

there only RX pin is used on board.

here (304.7 KB) is the px4flow circuit schematic.