You may be correct that this function is not implemented. We have not used the ultrasonic sensors in any internal builds. I will ask a developer about it. Meanwhile - as it turns out - We (the drone team in NXP) will be adding a bonus challenge to an upcomoing NXP RT1010 contest to implement a multidirectional ultrasonic sensor - you may want to look for that later this month. The intention is to offload the sening to the RT1010 MCU, and then communicate back via SPI/Mavlink.
