The GY-US042v2 Sonar is a very inexpensive, short range (up to 4m) range finder primarily designed for indoor use but which has been successfully used outdoors on Copter. It does provide more consistent height control below 4m than many barometers.
For I2C mode, set the RNGFND1_TYPE = “2” and no bridging of the three solder pads is required.
For Triggered Pulse mode, tie the center pad to “L” and set the RNGFND1_TYPE = “30”.
For Serial Mode, tie the center pad to “H” and set RNGFND1_TYPE = “31”. And set the Serial Port used to communicate with it to
SERIALx_PROTOCOL = “9” (Rangefinder) and
SERIALx_BAUD = 9 (9600).
This device has a maximum useful range of 4m, so set - RNGFND1_MAX_CM = “400”.
“CR” pin is either the SCL (I2C mode), Serial RX, or Trigger input
“DT” pin is either the SDA (I2C mode), Serail TX, or Echo output