Post updated.
I tested HM30 in UART RC signal input mode with RadioMaster TX16S loaded with OpenTX v2.3.14 and can report success.
One needs to connect 3-wires between the JR-bay of the radio and the HM30 ground unit RC signal input port for the UART communication mode of the HM30 ground unit to work:
- HM30 RC signal input port PPM/S.BUS/UART pin to JR-Bay CPPM pin,
- HM30 RC signal input port S.PORT pin to JR-bay SPORT pin and
- GND of JR-Bay to RC signal input GND
The original cable for the RC signal input port delivered with HM30 unfortunately does not have S.PORT pin included in the 4-pin JST GH connector, so one needs to crimp a custom cable for this.
For the interested I attach a Saleae Logic v2 capture of the PPM/S.BUS and S.PORT pins from cold start of HM30 ground unit and TX16S with OTX 2.3.14: HM30_TX16S_JR_Bay_OTX2.3.14.sal.zip (28.9 KB)
In the second logic analyzer trace with connected air unit, one can see in S.Port stream RSSI (dataId of telegram being 0xF101) packets with values 96 and 97 (32-bit values): HM30_TX16S_JR_Bay_OTX2.3.14_connected_air_unit.sal.zip (17.9 KB)
@SIYI May I suggest “MULTI” or “MPM” instead of “UART” for the third option in the GUI and in the documentation for the HM30 GU RC signal input, which would in my opinion make it more intuitive of what protocol is expected here, thus: “PPM/S.BUS/MULTI” or “PPM/S.BUS/MPM” instead of “PPM/S.BUS/UART”. It would be neat if the docu would also list that the S.PORT pin of the 4-pin port needs to be wired up as well for the third option to properly work. Thanks!