Am I correct in how to connect ELRS receiver to the Pixhawk 6c?

I’m new to ArduPilot so please bear with me. I’ve got a Radiomaster RP1 ELRS receiver which I now want to connect to my Pixhawk 6C. I know CRSF is a different protocol from ELRS, but in the short user manual which came with the RPI receiver it says

Wireless Protocol: ELRS 2.0 pre-installed
Bus interface: CRSF

So if I understand this correct, ELRS is what goes over the air, and CRSF is what the RP1 talks to the flight controller. Right?

In the Ardupilot docs on the Pixhawk 6c I read this:

To allow CRSF and embedded telemetry available in Fport, CRSF, and SRXL2 receivers, a full UART, such as SERIAL5 (UART3) would need to be used for receiver connections. Below are setups using Serial6. For the 6C Mini, SERIAL1 - SERIAL4 would need to be used.

I’m trying to wrap my head around this. So I need a “full UART” such as “SERIAL5 (UART3)” or later they also mention “Serial6”. In the Holybro docs I read that TELEM2 is UART5 and TELEM3 is USART2. I see no mention of SERIAL5, UART3 or Serial6 though. I know UART is a serial connection and as far as I understand USART2 is a more advanced version of UART5.

So since TELEM1 is used for the telemetry radio, am I correct in my assumption that I can connect the Radiomaster RP1 ELRS receiver to either the TELEM2 or the TELEM3 port on the Pixhawk 6c? Is either of them a better choice? Any tips are welcome!

For historical reasons the UART number often doesn’t match the serial port number on these ports. The serial port is what you configure. The UART number only matters if the manufacturer uses it for labeling ports. The 6C has 6 serial ports number 1-6 and any of them can be used with CRSF/ELRS since this is an H7. ELRS is an open source clone implementation of the closed source CRSF protocol from TBS. It refers to both the over-the-air protocol and the protocol used between the radio RX and the flight controller.

Thanks for clearing some things up. I’ve got a couple followup questions:

  • You’re saying the 6C has 6 serial ports. Are those six the 3 TELEM ports, the 2 GPS ports and the I2C port?
  • What is an H7?

Furthermore, in the Holybro docs I read the 6C has:

3 general purpose serial ports

  • Telem1 - Full flow control, separate 1.5A current limit
  • Telem2 - Full flow control
  • Telem3

Since Ardupilot docs say I need “a full UART”, does that mean Telem3 is not “full UART” (since only Telem1 and 2 say it has “Full flown control”)?

Google is your friend here.

You do not need flow control for ELRS so any UART can be used. “full UART” is not really meaningful in this context


I used SERIAL4 for my ELRS and using this web for setting
Ardupilot Setup - ExpressLRS

what’s the meaning of this sentence "RC_OPTIONS turn on Bit 9th which is “Suppress CRSF mode/rate message for ELRS systems”?
Because I cannot to change that parameter.

It just stops mode change spam in your GCS. You can set it through mission planner

1 Like

hi andy
could you solve my problem about ELRS ?
Setting ELRS to Pixhawk and Ardupilot Radiomaster TX16S - ArduCopter / Copter 4.3 - ArduPilot Discourse

I also have a problem with connection my radiomaster ER5a to pixhawk 6c
I even don’t understand which socket I have to use. plz help me)))
Binding is ok, but if I connect this receiver to ppm/sbus Rc socket nothing happened.

If you’re using an ER5A by default it will only output PWM signals, as it’s meant for controlling a RC Plane - so that won’t work with the Pixhawk. You can change what that receiver outputs to CRSF, but it involves configuring it differently from the receiver’s Wifi page as well as running master firmware currently. Or you can buy a different ELRS receiver that just outputs CRSF natively (these are much more common than the PWM type you have). Radiomaster RP1,2, or 3, Jumper, Betafpv all make models like this. Then you would wire that CRSF output into a serial port on the Pixhawk, TX to RX, RX to TX, 5V to 5V, GND to GND, etc.

1 Like

I unfortunately don’t have an answer to your question @svinozhop , but since I started this thread I do want to say that I did manage to connect my ELRS receiver to the pixhawk 6c I have. In the end I also had a problem with binding, for which I opened another thread here. Finally I concluded in the other thread all the steps that I took to bind and connect the elrs receiver to pixhawk and ardupilot.

Thanks for all your help here as well, and good luck to @svinozhop

Oh man… It was the second wrong receiver I bought…
Ordered RP3, will see.
Am I right I have to connect it to tele3 socket which has TX_RX pins?

Sorry to hear that, ELRS has a bit of a steep learning curve, but once you get it sorted, I find the system to be a very good one. Once you get the recevier, you can choose from multiple serial ports to wire it into that are UARTS. Make sure you’re looking here Pixhawk 6C Ports - Holybro Docs and here Pixhawk 6C 6C Mini Flight Controller — Copter documentation for that information on RC input/ports, etc.

I seem to be having some of the similar issues as everyone else here. I am using the TX16S and found that it was physically and some of the software very similar to my old Taranis, but that’s where it stops. I have watched just about every video and read almost every instruction manual on the topic and am more confused now than ever. I have found at least 6 or 7 ways to bnd and calibrate this setup but found onlly 1 document on my receiver which is a RadiioMaster RP3. My receiver is a Pixhawk C6 and my radio is a TX16S. I never knew that the RP3 wasn’t a plug and play so I had to solder the connedtions to an adapter that would fit in a 6 pin slot of the Pixhawk, and also since the receiver also provides telemetry back to the receiver it has to be connected to TELEM2. It will go into bind mode but every way that I tried to bind it to the radio failed. The receiver light eventually quits bind mode and just goes in to a fluttering red mode. I think that I am have to go back to the radio and try to setup a different model and try again. Ultimately I need onl 2 channels right now because it is for a boat, nothing fancy, but we are going to use QGroundControl so that we can play with long distance autonomous modes. If anyone has had any exoerience with this type of setup, give me a shout.

Hi @kramer65, like you I also want to connect TX16S ELRS version with RP1 ELRS 2.4ghz Nano Receiver with Pixhawk 6C.
I am new to this, I never even touched drones and I dont have any background, but I am trying to build a drone now.
I want to know what you did to connect RP1 ELRS with Pixhawk 6C? I mean physically? as they come in all pieces, how you soldered? with what kind of pins? I mean how many number pin cable you used and so on. If you can help me with this, its going to be great help.

Hey Guys,
Head over to the ELRS Discord, and accept the invite: ExpressLRS Community

Go to Help And Support, and sift thru the posts…those guys answer the same questions countless times a day…and are very helpful. One needs to upgrade a new ELRS RX, easily done over a WiFi link.

Download the ELRS Configuration PC app: ExpressLRS-Configurator-Setup-1.6.0.exe
(also available for Mac and Linux) Get this before hitting the guys on the Discord.

I run ELRS 100% now, on FC’s ranging from original 3DR Pixhawks thru Zealot H743 FCs. Painless, just works, especially on a TX16s…

Bit of a learning curve, but pretty minor considering other things.


1 Like

Joined, thanks for your suggestion.

Hello all ,I would like to continue my doubt over here. I am also pretty new to this field ,
I am in trouble , hoping you guys could help me, this is my first build with Pixhawk 2.4.8 and Mission planner. I am planning to buy TX12 Mark II Radio Controller (ELRS version).

I am not sure if this is the best thing , but I have decided to purchase RP3 ExpressLRS 2.4ghz Nano Receiver for my TX12 Mark II Radio Controller (MODE 2 , FCC,ELRS version).

please help me choose a receiver, I am unable to figure out what is needed for my quadcopter and also what is the difference between RP1 ,RP2,RP3 ELRS Nano Receivers and ER4 ER6 ER8 2.4GHz ELRS PWM receivers? please help me and also do I only have to buy the receiver or any other extra hardware with it to make it work with Pixhawk 2.4.8 and mission planner ?

@andyp1per #hardware-discussion:pixhawk #ground-control-software:mission-planner #ardupilot #hardware-discussion:radios-hardware

RP3 works fine, I run one here. The primary difference in those RX is form factor and antenna.
Make sure to check out the guide: Crossfire and ELRS RC Systems — Copter documentation , as there are some Arducopter parameters that you need to configure.

Your TX will have to be set for CRSF - I believe the TX12 is native ELRS so it might not require any special setup.

The ELRS / EdgeTX forums (which you joined) should help you over issues.

1 Like

Thanks a lot for your confirmation @CharlieKeck

In that case I am going to proceed buying RP3 ExpressLRS 2.4ghz Nano Receiver for my TX12 Mark II Radio Controller (MODE 2 , FCC,ELRS version). As it works with Mission Planner and Pixhawk 2.4.8.

Am I correct ?

And also could you suggest me some good telemetry for my Quadcopter, Like in the place where I am planning to test and fly the quad there are a lot of things which run in 2.4GHz and 5GHz,(the whole area almost is covered by the University’s Wi-Fi.)