Setting up SRXL2 Protocol Receiver in ArduPilot Firmware

I. Principle

SRXL2 is a digital single-wire serial communication protocol for efficiently transmitting RC transmitter signals to the flight controller system. The flight controller can read signals from the SRXL2 receiver through the TX port to control the aircraft.

II. Equipment Preparation

Hardware
1) Flight Controller: Any of the following flight controllers are suitable for this tutorial: SpeedyBee F405 WING APP / SpeedyBee F405 WING MINI / CoreWing F405 WING V2
2) SRXL2 Receiver: Such as Spektrum SPM4650
3) RC Transmitter: DSM protocol compatible transmitter
4) Computer (for ground control station configuration)
5) USB Data Cable (for connecting to the flight controller)
Software
   Mission Planner ground control station

III. Specific Operations

1. Wiring

1. Connect SRXL2 receiver to flight controller:
      5V → 4.5V (power supply)
      GND → GND (ground)
      Signal → TX2 (signal wire to TX2 port)
   
   2. Binding Receiver
2. Enter binding mode:
          Press and hold the BIND button on the receiver while powering on. Observe the receiver's indicator light flashing rapidly, indicating it has entered binding mode.
   
3. Select DSM protocol on the RC transmitter:
          Enter the RC transmitter MDL menu, navigate to the SETUP page, select the DSM protocol, and press the Bnd (bind) button to bind.
   
4. Confirm successful binding:
          If the receiver's indicator light changes to a steady state, the binding was successful.
   3. MissionPlanner Ground Control Station Setup
5. Connect the flight controller to the ground control station using a USB data cable.
6. Enter parameter configuration: click Configuration/Tuning → Full Parameter List. In the search bar, enter the following parameters and modify their corresponding values:
   
   For SpeedyBee F405 WING APP/ SpeedyBee F405 WING MINI, modify the following parameter settings:
   | Command | Value |
   | --- | --- |
   | SERIAL1_PROTOCOL | -1 |
   | SERIAL2_PROTOCOL | 23 |
   | SERIAL2_BAUD | 115200 |
   | SERIAL2_OPTIONS | 4 |
   | RSSI_TYPE | 3 |

For CoreWing F405 WING V2, modify the following parameter settings:

Command	Value
SERIAL1_PROTOCOL	-1
SERIAL2_PROTOCOL	23
SERIAL2_BAUD	115200
SERIAL2_OPTIONS	4
RSSI_TYPE	3

3. Click "Write Parameters" to save the settings.
   
4. Restart the flight controller: Disconnect the flight controller from the ground control station and power it back on.
5. Verify functionality: Go to the RC transmitter calibration page and ensure that all channels have normal feedback. If the channel data changes normally, it indicates that communication between the receiver and flight controller is working properly.
   
   ※If there is no data, please check the parameter settings and receiver wiring.

IV. Q&A

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