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PPM, CPPM, S.Bus???? R620X problem with Pixhawk...

#1
So I have an R620X receiver. I bought it, bound it, and tested it with a servo. All good.

Then, I went to connect it to my Pixhawk, and got nothing. The R620X is advertised and a CPPM receiver, which should work just fine with the Pixhawk, but I got nothing. Just to be sure it wasn't me being silly and doing something wrong, I connected my R615X receiver in the exact same way. It worked!

I decided to contact hobbyking, and they were very nice. They actually sent me two replacement R620X receivers!!! But, perhaps unsurprisingly, neither worked. I also bought an R1020X to see if it's any different. That will arrive tomorrow.

It's not just the Pixhawk, because I've done the test on 3 different Pixhawks, so what's going on here?!?!

I'm very unhappy at this point, because I've been forced to do all my testing using a single satellite receiver connected to the Pixhawk's DSM port, which does not supply anywhere near the range I feel safe with. My ideal setup is a full range receiver connected two the Pixhawk through the S.Bus/PPM port with 1 or 2 satellites connected to the receiver.

Please let me know if this is an issue you've experienced, or know how to address!!
 

makattack

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#2
I'm not familiar with that RX, but using a FrSky RX and ORX LRS with SBUS on my Pixhawk, I initially had no luck when I connected it to the "SBUS" pin -- not reading the documentation clearly, I only found out later that it was the SBUS output pins. If you connected to the RC pins, it should work.

Note, that for the FrSky stuff, I just connected and it worked... for the ORX LRS RX, I needed an inverter for the Pixhawk to work.

http://ardupilot.com/forum/viewtopic.php?t=5425&p=8423
 
#3
I initially had no luck when I connected it to the "SBUS" pin -- not reading the documentation clearly, I only found out later that it was the SBUS output pins. If you connected to the RC pins, it should work.
Thanks for the reply. I'm aware of the funky naming of the ports on the Pixhawk and I have been connecting the RC IN port. S.Bus is for S.Bus output.

for the ORX LRS RX, I needed an inverter for the Pixhawk to work.
It was my understanding that Pixhawks have the inverter hardware built in so that they can handle both types of signal. I think this is corroborated by the fact that the R615X receiver worked just fine, but maybe it's a different protocol? They are both advertised as CPPM on the HK site.
 

makattack

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#4
Yeah, I took a look at the product page and manual for that RX (620X) and it's confusing. It says the BIND port is where the CPPM or S.BUS output signal is, but it doesn't say how to select one vs the other.

BIND - Triggers binding procedure if receiver is powered with the bind plug inserted in this port. In normal operation it is a 12 channel cPPM or
s.Bus output (depends on the model of the receiver you purchased)
They say it depends on the model of the RX, but the product page says it supports both. Sorry. If you have an oscope or a computer with a serial input, maybe you could hook up the output of the bind signal pin to see if it's a digital vs analog signal?

Yeah, the pixhawk has a built in inverter, but if you have a RX like the OrangeRX LRS which only has "serial" output -- not specifically S.BUS, and the S.BUS is implemented in software (OpenLRSng) but since there is no hardware inverter on that RX, the inverter on the Pixhawk ends up not canceling out the signal.

The inverter on the pixhawk is normally used to un-invert the normally inverted signal coming from RX's.

I guess that could be another problem... is the ORX 620X sbus setup is designed to not invert the signal like the ORX LRS, maybe you need to invert it first?
 
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#5
I have a friend who can check it with an oscilloscope for me. Now you've got me worried my R1020X isn't going to work either...

Well, in the interest of finding a receiver that will work, do you think I could expect to have the same issue with the LM0007 by LemonRx? I've been googling this stuff and am finding very little documentation about compatibility outside of 3DR's page, which seemed to suggest that the R620X should have been fine. And I still don't understand why that R615X gave me no issues...
 

makattack

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#6
If this is the LemonRX: http://www.lemon-rx.com/shop/index.php?route=product/product&product_id=118 model you're planning on using, it says PPM output, which I think should work. The problem with the OrangeRX 620X is that it says it supports both, but doesn't tell you how to select or set it up. PPM is a just a more known protocol, and is simpler than SBUS. I think SBUS for RC control output to flight controllers is still a newish development, so documentation will be a little light. I had to do a bit of "figuring out" to get SBUS working on both the APM and Naze/Cleanflight platforms. Primarily around setting up serial ports, determining the need to invert or not, and even hacking a RX that didn't have a SBUS output (X4R) to give it SBUS out.
 
#9
The 10ch didn't work either (surprise surprise). I picked up one of the LemonRX receivers and I will try to make an inverter tonight
 

makattack

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#10
Ah ha. A closer look at hobby kings site shows that they sell those rxs in ppm or sbus models. They don't support both. Do you know which versions you bought? It's not hard to make an inverter cable, and they are cheap to buy as well, but it wouldn't be necessary if you have a ppm rx.
 

bobzwik

Junior Member
#12
Hello! Any update on this?

I'm interested in purchasing a HKPilot32 (HobbyKing Pixhawk equivalent), and I currently have a Spektrum DX5e radio. If I take it that the HKPilot32 is the same as the Pixhawk in terms of inputs, my only option is to use DMS2/X satellites, or a DMS2 compatible receiver using the S.BUS port (source : https://pixhawk.org/peripherals/radio-control/spektrum_dsm)

As you probably have realized, HobbyKing advertised the R620X as both CPPM and SBUS, but this is not true. There are 2 different models.
SBUS : http://www.hobbyking.com/hobbyking/...CompFullRangeRx_w_SatDivAnt_F_Safe_S_Bus.html
CPPM : http://www.hobbyking.com/hobbyking/..._CompFullRangeRx_w_SatDivAnt_F_Safe_CPPM.html

So I'm guessing that the S.BUS version should work, right? If someone has confirmation on this, please come forwards!

Also, unfortunately, both R620X have been back-order for a while now, as well as the rest of R--20X line, except for the R1020X. But 10 channels is way more than I need.
 
#13
The 10ch didn't work either (surprise surprise). I picked up one of the LemonRX receivers and I will try to make an inverter tonight
Hi did you find a fix for the orange R620X V2 issue?? I am having the same issue with a Naze 32 trying to run cppm. I have 3 RX and none will communicate with the Naze. Yet I go back To the R615X V1 and it works perfectly...
Cheers