S-Bus not detected on Pixhawk with FrSky X8R

I try to connect a FrSky X8R (in Mode 4, other modes also tested) from its s-bus out (not s-port) to The Pixhawk RC connector (not SB).
In Radio Calibration the signals coming from the X8R seem not to be connceted.
Is there any test I can do, as I now think that the Pixhawk is a DOA…

If you have any PPM receiver, it would be interesting to know if PPM works - just to figure if it’s a hardware or software issue.
What version of Copter are you using exactly?

unfortunately I only have X8R receivers. To be sure its not on the receiver side I tested it on a NAZA, works perfectly in s-bus. (For double check I used a second X8R, also changed servo cables to be sure)
Accoording to your suggestion I posted my problem here, using APMcopter V3.1.5 but also tried now V3.2 RC2, no results!
the setup is as follows:
Pixhaw+ buzzer+Gps compass+ 8XR contected via USB on the desk (no esc, no frame, no motors, just the boards)
LEDs on the Pixhawk:
Main LED: double orange blinking
FMU PWR: green
B/E: off
IO PWR: green
B/E fast orange blinking
ACT: Blue (slower blinking than B/E)

It works for me. I guess you are plugging it into the SBUS out channel, not the RC-IN channel. the RC in determines if the signal is PPM or SBUS and configures itself automatically.

Wait a second… THAT shouldn’t be. Both B/E should be off after boot. That sounds like your I/O module is unhappy with something. Do you get any “unusual” tones?

This is how it’s supposed to be:


as said: Sbus out from 8XR to RC of Pixhawk.
Melody exactly the same as on youtube video.
then 4blink sequence on arming button. long hold of arming button gives a steady red
I think the Error LED (double yellowv or orange blink on central LED) is normal, as there is no RC calibration made (simply because its not possible :slight_smile: )

a small video including LED and audio
dl.dropboxusercontent.com/u/680 … xhawk1.MOV

To help I have just tested and verified X8R does work with SBUS on PH.

which confirms more and more a faulty PH. Would you mind sending me your Taranis eep? (I think thats the name of the taranis settings).
I suppose your X8R is also in mode 4 and the Taranis in D16, ch1-ch8?
at least something should come in on PH???

[color=#00BF00]I moved this to the hardware section now, as it seems that your I/O module is unhappy.[/color]

Can you post all files you find on the SD card?

I have tested with AC3.1.3 and AC3.2-rc2 beta and it works ok.

I’ve included a picture of the connection I used (sans USB cable)

PS: If you can post a picture of your connections that would be helpful. If that isn’t the issue it seems it a fault on the PH

Wiring seems coorect to me as in my short video…
dl.dropboxusercontent.com/u/680 … xhawk1.MOV

FYI the logs: What I do not understand is why since some days no more logs are recorderd? Anyway, the problem did not change

I returned my Pixhawk to the Dealer, unfortunately they only could test with an FrSky D4R with PPM, and this works. As far as I understand S-bus is not exactly the same than PPM, or is it?I still cannot believe, that the Pixhawk is not faulty and I cannot imagine what I could do wrong on the Taranis side.
I highly would appreciate if somebody could share a Taranis/X8R setting with me (eep file I think), which is certain to work…thanks to all!

I will almost guarantee you that the IO firmware is not correct. Have your dealer power up with the safety button pressed to force the firmware in the IO portion of the Pixhawk to update.

Thanks for the advice, I already did that before sending it back, no help. :frowning:As I am not an absolute expert, can somebody confirm, that PPM and S-BUS is not 100% the same?

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maybe I need this S-bus to PPM transcoder? frsky-rc.com/product/pro.php?pro_id=112
Eventhough I was convinced it should work straight away with the X8R…

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(C-)PPM is a sum signal in which all PWM (servo-) signals are represented by specific timing.
=> en.wikipedia.org/wiki/Pulse-position_modulation
S.Bus is a proprietary digital protocol, originally invented by Futaba for their products but it has become a semi-standard.
=> futaba-rc.com/sbus/

thanks Stefan, this is more or less what I also found out. If my dealer says it works on PPM (FrSky 4Dr) it does not necessarily mean it works on S-BUS. Probably the IO part of the pixhawk is really faulty.

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