How to connect RadioMaster 2.4GHz RP1 ELRS FPV receiver to Pixhawk 6c?

Hardware Pixhawk family
1

(this is my first post) How do I to connect a RadioMaster 2.4GHz RP1 ELRS FPV receiver (RP1 V2 ExpressLRS 2.4ghz Nano Receiver – RadioMaster RC) to Pixhawk 6c?

RP1 has 4 pads (5v, GND, TX, RX).
(1) Can I connect those pads to the Pixhawk 6c TELEM2 (https://docs.holybro.com/autopilot/pixhawk-6c/pixhawk-6c-ports#telem-2-port) VCC, TX(in), RX(in), and GND.
(2) Does RP1_TX connect to 6c_RX(in)?

I have scoured the internet for this basic info, and could not find anything. Am I missing something basic here? Thanks to anyone who can tell me what to do before I try the wrong thing.

2

Here is the easiest way to “scour” the internet and arrive at the respective Ardupilot Wiki page:
Google “Ardupilot ELRS” or “Ardupilot pixhawk 6c”

3

I have looked there. And watched a lot of youtube videos. And some good Ardupilot docs. And I keep notes. Lots of them. My gdrive is _AI_DRONE - Google Drive. But nowhere have I seen anything about the physical connection of the RPx to the Pixhawk x. I thought the RP1 might have info (User Manuals – RadioMaster RC), but for the RP1 a one page doc, half in Chinese (https://cdn.shopify.com/s/files/1/0609/8324/7079/files/RP1.pdf?v=1669084468).

PS: My other docs at HITL1 PX4 · terrytaylorbonn/auxdrone Wiki · GitHub, ziptieai.com.

4

I have spent months going thru full simulation, then the AI stuff (on PI4, Nano), then HITL. HITL with jMAVsim with 6c works, with the Nano doing AI object recognition and sending Mavlink (pymavlink) to the 6c to land when my face recognized. I did this without assistance (well, Ardupilot/PX4 sites, Youtube, stackoverflow, etc… whithout them I could do nothing; the Intelligent Quads video series got me thru the simulation part; I did that series several times before I got it right).

So I am used to answering my own questions. But now I have this new RP1, and I am stuck :slight_smile: Until now I have been focusing mainly on non-hardware issues… but now finally putting together a real copter (slowly…).

I tried to connect to the 6c a few a days ago from Win11 Mission planner to TELEM2 via FTDI, but something is not right (my wire splicing is horrendous, anything could be wrong). I could do it though via a USB from Win11 to the USB port (on the front face, not the side) of the 6c. All documented (roughly on that Gdrive and wiki). So I am a newbie to this forum, but not so much a newbie to some aspects of drones.

5

Short answer “yes”. Long answer:

Everything you need to know can be found on the CRSF and ELRS wiki page.

(1) You can connect an ELRS receiver to any full-duplex serial port of the 6C, including telem2.
(2) Receiver RX goes to FC TX and vice versa. On the wiki page they used Serial4 as example, with telem2 on 6C you’ll need Serial2, as seen here.

6

Thanks Janno. I just need a simple example, one way of exactly how it is done. There is no RC club around here where I live, I have no RC friends. I’ve watched 10 youtube videos (Bardwell, Painless 360, etc) about configuring the RP1 receiver, the tx12, the lua scripts, etc… Ok, I understand how its done. But I hesitated to do this without knowing more detail, because I only have 1 FC (6c) and dont want to blow anything up (hardware scares me … in particular, does Rx go to Tx? ). Specific examples are really quite helpful to newbies .

7

The worst that can happen when you connect it wrong is to that you blow out your receiver.

Receiver RP1 → Pixhawk 6C telem2
GND → pin 6 (GND)
+5V → pin 1 (VCC)
TX → pin 2 (RX)
RX → pin 3 (TX)
8

Bingo! Thanks Janno. PS: The RP1 was something like $15… I am worried about the TELEM2 port. Hope I did not screw it up already while trying FTDI :slight_smile:

10

FYI, it took me a over 2 days to get it connected. I had to first install 2.5.2 on TX/RX, then downgrade Python to 3.11 on my PC. But in the end it worked. Much more complicated than I thought. Maybe I did something wrong. In any case, this document describes in details what I did. Thanks again @Janno for the help. 3.1-3b_hitl1_px4_connections_RC-TX_RP1-RX_v20_24.0324.docx @ 3 HITL (real FC) - Google Drive