Hello and thank you to all ahead of time for any help,
I am currently assembling a HolyBro S500 v2 kit with the hopes of using a Spektrum DX6e transmitter and a AR620 or SPM4650 receiver. I had feverishly ordered everything thinking I had everything I needed until I came upon using the DSM/SPKT connector for the receiver. Closer inspection of the kit upon arrival yielded a cluster of wires that weren’t intuitively usable with a Spektrum receiver. According to the PX4 documentation from this link, Radio Systems · PX4 v1.9.0 User Guide, all Spektrum DSM RC receivers are compatible and must be connected to the SPKT/DSM input.
With the understanding that the cables have to connect via the SPKT/DSM port, I thought there would be a turnkey cable available from HolyBro/ Spektrum with the kit but that does not seem to be the case. For hooking up the receivers, I searched the forums and looked at the Pixhawk 2 and Pixhawk 4 pinouts. The number of pins went from three on the Pixhawk 2 to five on the Pixhawk 4. I am currently continuing forward with trying to make a custom wire with a 5 pin JST-GH connector to 4 pin JST-GH connector to the SPKT/DSM port, but am unsure about which of the new pins are necessary. I know that there were initial SRXL2 incompatibilities with Pixhawk that have been resolved since its release.
Pixhawk 4 DSM RC Port
Pin Signal Volt
1(null) VDD_5V_SBUS_RC +5V
2(yellow) SBUS* +3.3V
3(null) RSSI** +3.3V
4(red) VDD_3V3_SPEKTRUM +3.3V
5(black) GND GND
- Connect SBUS or DSM/SPKT receiver’s signal wire here
** Sends the RC singal strength
2 N/C (No Connect)
Included Pixhawk 4 DSMX receiver cable
5 pin JST GH to 3 pin Molex Picoblade
The supplied DSMX receiver has cables on the 2,4,and 5 pins.
I was going to strip the molex picoblade end of the wire and solder it onto the SPM4650 pins with the following connections:
DSM/SBUS RC Port => SPM4650
2 (SBUS* +3.3V) => 1 (S)
4 (VDD_3V3_SPEKTRUM +3.3V) => 3 (+)
5 (GND) => 4 (-)
Would this be an appropriate connection for the Pixhawk 4 and a Spektrum receiver or have I missed the boat entirely?
Any circumferential information, sources, or advice would be appreciated as the PX4 documentation did not specify any recommended Spektrum transmitter/receiver pairs so this would be a chance to expand upon that.