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FPort for RC Control and Telemetry setup on F4 FC

I am building a 5" quad running arducopter 4.1.0 dev, and the goal here is to use FrSky FPort, supported on version 4.1.0 dev and later.

Getting this to work was getting frustrating for me and was very hard to setup until then suddenly, the right pieces of information clicked and it was easy. For anyone’s benefit that can find this information useful, here it is.

Flight Controller: Matek F405SE, Arducopter 4.1.0 dev
Receiver: R9MM receiver and R9M 2019 Module

For additional reference:

High level steps:

  • Flash 2009 R9M Flex Firmware on Transmitter Module (R9M_FLEX.frk)
  • Flash 2009 R9MM Flex Fport firmware on receiver (R9_MM_FLEX_Fport.frk)
  • Connect receiver to G, 5V, Tx5 or Tx3 on Flight Controller, per wiring diagram. (Would not work on Tx2)
  • Set Serial5 Baud 115
  • Set Serial5 Protocol 23
  • Set Serial5 Options 7
  • Set RSSI_TYPE = 3
  • Run Yaapu Telemetry script on radio (TX16S)
  • Discover sensors with Yaapu running, this is needed to discover sensors with passthrough telemetry from FC

Something that caused me trouble is that I expected this to work on TX2 and I tried many things until I decided to use TX3 and TX5 to test. Would work on the later 2 but would never work on the former.

I build a dual motor plane on XUAV goose frame with Pixhawk 2.4.8 + Frsky X9d Pluse (OpenTX 2.2.3) with R9M Flex + R9mm (Flex). but not work with fport config.

Following are my config:
FC: pixhawk 2.4.8 from China
Receiver: R9MM with R9M Module (Flex F/W)
Arduplan fmuv3 4.1 beta(2021/05/15)

Wiring : R9MM Inverted F.Port pin --> TELEM1 TX
SERIAL1_BAUD:Tried 57,115
SERIAL1_OPTION : Tried 4 , 7 , 160
SERIAL1_PROTOCOL: Tried 4, 10 , 23
RSSI_TYPE = Tried 0,3


  1. Radio No Signal on FC (Servo can not move and No response on Mission Planner)
  2. Transmitter got connection and have telemetry signal
  3. run Discover new sensor on x9d plus alway got 2 sensors only (RXBT ID:248/ RSSI ID:248)

any body have idea how to resolve ? thanks

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