Clarification of RC receivers compatible with Pixhawk

After much searching through many threads on and off of DIYD, I think I can say with some… confidence that this page offers misleading or incorrect information about which FrSky receivers are capable of PPM-Sum or CPPM outputs to the Pixhawk’s “RC” input/port.

Section 3.4 states “…support PPM-Sum or S-Bus directly”, however a lower section “FRSKY TRANSMITTER ADAPTER MODULE AND PPM-SUM RECEIVER” implies (to me, anyway) that the pictured V8FR-II receiver is directly compatible. However it appears that it is not, unless one buys the 3DR PPM Encoder to use with that receiver. At the moment, my understanding is this: If you have a Turnigy 9X that has been modified with the pictured FrSKY DJT transmitter module, then you should buy the “FRSky Delta 8 MultiProtocol PPM-Sum Receiver” or the FrSky X8R.

If my understanding is incorrect, or you have other insights to offer, please speak up! And, is this posting the best way to alert someone to improve the subject page on the wiki?


Yes, this is the best place to ask questions about wiki pages! In response to your question, Pixhawk is directly compatible with PPM receivers. If you are using a PWM receiver, you will need to use a PPM Encoder to translate into PPM before connecting to Pixhawk.


Thanks for the quick reply. It is difficult to discover the specifications of the V8FR-II receiver, to determine if it is, or is not capable of PPM-Sum output. Apparently it is not.

Is there someone who will take responsibility for updating the wiki page, to avoid others purchasing an V8FR-II or the upgrade kit, with the incorrect assumption that the V8FR-II is directly compatible with the Pixhawk’s “RC” input?

FRSKY TRANSMITTER ADAPTER MODULE AND PPM-SUM RECEIVER" implies (to me, anyway) that the pictured V8FR-II receiver is directly compatible.
However it appears that it is not, unless one buys the 3DR PPM Encoder to use with that receiver.

Where are you reading that the V8FR-II is not? … elta-8.pdf

it outputs PPM sum that can be fed directly to the Pixhawk or PX4

08:55AM comment by Amedee here: “Right, V8FR-II is not CPPM, so you have to connect all channels. Actually, only D4R-II and D8R-XP are CPPM compatible (plus some older discontinued models). D8R-II plus is not CPPM either (unless you flash the the D8R-XP firmware, but then you have a D8R-XP…).”

And see the followup comment by neBstress.

Um, isn’t that attached pdf about the Delta receiver, rather than the V8FR-II?

Thanks. We’ll have to investigate.

I see now on the pdf attachment for the Delta 8, that the “FrSky V8” series of receivers can be used with a jumper over pins 5 and 6. I would not have thought to search a Delta 8 spec sheet for that crucial bit of information! Thanks again.

Argh, my mistake on reading the Delta 8 sheet. The illustration is for binding only. The jumper should be across pins 3 and 4 to result in PPM-Sum output. I am assuming that “PPM-Sum” is an equivalent concept to “CPPM”…

Hi uvtaxonaomy,
I am afraid your original analysis was correct, it does not appear that the V8 receiver is PPM-Sum / CPPM compatible regardless of interpretation of the Delta 8 PDF. :frowning:

I have since fixed the Wiki page to make this clearer: :confused: … ter_Module

FR-Sky does have several PPM-Sum compatible receivers and several that are not.

You need to check at the FR-Sky web site itself for compatibility information.

PS. If it did actually turn out that you were able to get a PPM-SUM connection by installing that jumper I would really appreciate your mentioning it here so I can try to figure out what is really going on!!!

Best Regards,


Thanks Gary! I just posted a topic on the FrSky Forum. Maybe that will lead to an informative reply:

“I did not find the information I needed on the FrSky spec sheet for the V8FR-II. However, I was directed to read the spec sheet for the Delta 8 receiver, where there are some instructions that appear… to apply to (a) binding the V8FR-II to a Turnigy 9x with the DJT module, AND (b) to enabling PPM-Sum output from the V8FR-II (by adding a jumper to pins 3 and 4). The best result that I have achieved is the 9x’s DJT module (switch 1 off, 2 on) has a solid red light and a flashing green light. On the V8FR-II, both LEDs are solid on. However, my 3DR Pixhawk does not appear to recognize signals on the RC input/port. Any ideas? I suppose that the instructions with the Delta 8 may require a contortionist or two people to successfully bind the 9x and the V8FR-II, and if so, OK. Very difficult to know from reading the instructions.”

I have ordered a Delta 8 receiver (it was hard to find any FrSky X8R receivers in stock). If that was an unfortunate purchase, and I need to order a D4R-II, I can do that. Be nice to get my quad drone in the air some day! :slight_smile:

Hi uav,

Doing it on the Delta 8 required some pretty tricky manuvering as well, propping a stick against the desk to hold the receiver bind button down for instance, but necessity is the mother of invention.

Unfortunately I really don’t think you are likely to be successful at using the V8, you shouldn’t have any real trouble binding it.

But I don’t think your ever going to get a PPM-Sum (yes same as CPPM for our purposes) signal out of it. :frowning:

Even though the receiver (now) shown is a 4 channel, 8 channel ppm-sum is still passed through.

And that is a small and inexpensive receiver.

I see you are ordering a Delta 8, I am very happy with this receiver and I think you will be as well.

Hmm guess I should mention that in the wiki too. :wink:

Best Regards,



Would you mind to update the 3DR PPM encoder information, please? it seems to be the old version is not available any more at the store

Hi Rogelio,

I have updated the 3DR PPM sum info and supplied a link to the store.

Best Regards,


Gary, thanks for all your help, and for updating that wiki.

History: A while ago I was able to bind the V8FR-II to the 9x (modified with the DJT module), and test with a small servo. So I could believe that the 9x and the receiver were communicating.

So your tip confirmed my suspicion that binding the Delta 8 will require a bit of physical ingenuity, or two people! :smiley:

Hi Gary,
Just received a FrSky Delta 8, and I can now see radio controls indicated in Mission Planner. Wahoo! And the binding procedure wasn’t as difficult as might seem from reading the FrSky instructions (there are at least two, literal interpretations. The simpler interpretation worked for me.).
No rush from me, but some readers may wonder if is relevant to using the Delta 8 for some advanced capability.
Thanks again.

Uvtaxonomy, do I still need to flash a new firmware if I have a recent delta 8 you think?