Problem with connecting Spektrum receiver to pixhawk 4

#1

Hello everyone! I’m newbie in drone using and I trying to set everything up.
I’ve got pixhawk 4 flight controller and Spektrum AR9030T telemetry receiver.
The problem is that when i connect my whole receiver to pixhawk through DSM\SBUS port (as you may see in the picture)

I have some lags. The receiver connected, but in qgroundcontrol in Settings\Radio
dots wich represent each chennal are stuttering or flickering or i don’t how to say it. They are just moving inadvertently without me touching any sticks at the TX.

In the same time, when i connect a single Spektrum satellite, everything is just fine, i don’t have any lags.

Maybe the problem is because it shows 16 channels in qgroundcontrol, and my receiver has only 9 channels. I’ve already tried reducing rc_chan_cnt parameter to 9, but nothing happens.
Any help is appreciated.

P/S I apologize for my English. It’s not my first language.

#2

As far as I know Spektrum does have only few Receivers that have SBUS/PPM (like AR7700), most are all single PWM Signal Receivers, despite the Satellites themselves have the signal towards the main receiver. In order to use it with Pixhawk you need a PPM Encoder where you connect all your PWM Channels to a small board that encodes them together in one PPM Signal that goes to the Pixhawk PPM Input.

#3

It is written, that my receiver support DSMX technology. As I’ve understood, this is a digital protocol, which is similar to SBUS. And it is written that pixhawk understand this DSMX technology as well.
Maybe I was not correctly at the post before. For example, when i moving THR stick, the throttle dot movse on the screen, but simultaneously other dots are chaotically moving to. What i wanted to say is that it works but with a big lags. I can’t even make a calibration because of this flickering.

#4

DSMX is a Radio Protocol invented by Spectrum. Before there was DSM2. However this is not a Signal Protocol that transfers Data from your Receiver to the Pixhawk. Pixhawk is labled DSM2/DSMX compatible since it is able to talk to a Satellite directly and bind it to a Spektrum TX. Sadly most Spektrum Receivers do not expose this signal on the Pins (except some newer ones like AR7700).

This is my knowledge when I left the “Spektrum World” about a year ago. I had a Spektrum 7s System with which I used a PPM Encoder to hook it up to a Pixhawk. But maybe my Information is outdated.

#5

Thank you for the answer. I’ve already ordered PPM encoder, but i heard, that ppm has high latancy and i wanted to have max of performance.

#6

Have you tried connecting just one of the Satellite Rx to the DSM port? I believe that’s what it’s for (or if you have an SBUS Rx like the FrSky X8R) then do your Radio calibration. I have my QuadRanger with a 36" extension and the Rx mounted on top of the vertical fin and works well. I use the unused ports of the Pixhawk 1 for servo output to control the gimbal.

Good luck.

#7

Yes, I have, and everything is just fine. But I want to use the whole receiver with both remote satellite RC receivers for better connction.
I’ve already ordered PPM encoder, but as i said before I want at best latency as possible.
The special output on telemetry receiver called “SRXL”. Does anybody know what that means? Do I have to connect this receiver through this port to pixhawk? Maybe this port is made for something else?

#8

Posted on this the other day QGroundControl: How to Spektrum Bind when connected to Pixhawk

Get an AR7700 if you want an easy install and 22ms default, use the DSMX port and you can get the low-latency (7.5ms) modes from an AR9030 (Spektrum Black).