Hi. I recently bought a clone PX4FLOW , which MB1043 sonar is not pre-mounted on PX4FLOW board. I mount MB1043 but find no distance reading in QGC. After a few days of try-and-error. I find TTL jumper on the back side of MB1043 need to be soldered (which is not solder by default when MB1043 is shipping). According to MB1043 datasheet, "solder the TTL jumper pads on the back side of the PCB… enbale TTL output for pin 5 ". I hope it will help some people.