PPM pinout

PX4 Autopilot Flight Controllers 💻
1

I’m starting to set up a new Pixhawk 2.4.8. The kit contained a PPM Encoder, presumably to interface between my Orange Spektrum compatible receiver and the FCB. It included a wiring harness to connect the PWM outputs from the receiver to the encoder, but not from the encoder to the FCB. The encoder has labeled pins for GND, +5V, PPM, and MUX. The FCB has 3 pins, presumably for +, -, and signal. I have some leftover connectors with pigtails from other projects that I could use to make my own wiring harness. The connectors fit the sockets on the encoder and the FCB, but I don’t know which pin is which on the FCB socket, and the wire colors on the pigtails aren’t helpful.
Can anybody help by identifying the 3 pins in the SPKT/DSM socket on the 2.4.8?
Thanks

2

So the PPM encoder does not connect to the SPKT/DSM socket. The SPKT/DSM socket is for the Spektrum satellites if I remember correctly. It speaks some serial protocol, but not PPM. The PPM connector should connect to the RC in pins, at the very end of the servo rail. It should be labelled RC IN. It should be +, -, signal like the servos next to it.

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3

Thanks for the help. I’ll dig through the various wiring harnesses that came with the rest of the stuff to find one with the appropriate connectors. On the same topic, does the MUX pin on the output socket of the encoder have a purpose?

4

Search for mux in the manual: https://download.ardupilot.org/downloads/wiki/advanced_user_tools/PPM-Encoder-3DR-Manual-v2.3.16.pdf

5

Thanks again for the info and link. Having the documentation is immensely helpful.

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