Getting Started with ArduPilot Serial Receive and Transmit Blocks

R2026b

This example uses:

This example shows how to configure two ArduPilot® telemetry ports for bidirectional loopback communication using Serial Transmit and Serial Receive blocks in Simulink®.

You configure matching serial settings, align the Serial Receive block parameters with the transmitted data, and verify the exchanged values in Monitor & Tune or Connected IO mode.

Required Hardware

This example requires the following hardware:

ArduPilot Series flight controller
Micro USB Type-B cable
JST-GH 6-pin connector

Configure Software and Hardware for ArduPilot

Install the UAV Toolbox Support Package for ArduPilot Autopilots. For more information, see Get Started with UAV Toolbox Support Package for ArduPilot Autopilots.

Set up and configure your ArduPilot hardware. For details, see setup and configuration.

Load Project

To open the example project:

openExample("ardupilot/SerialDataReceiveTransmitExample")

The project contains the Simulink model ReceiveTransmitSerialData.The model connects Serial Transmit blocks on TELEM2 and TELEM3 to send attitude and angular velocity data, with corresponding Serial Receive blocks on the opposite ports.

Set Up Loopback Wiring

Create a loopback communication path between TELEM2 and TELEM3 ports so that each port receives the data that the other port transmits.

Connect Tx pin on TELEM2 to Rx pin on TELEM3.
Connect Tx pin on TELEM3 to Rx pin on TELEM2.
Connect the ground (GND) pins of TELEM2 and TELEM3 to establish a common signal reference.
If you use hardware flow control, connect the request-to-send (RTS) pin on TELEM2 to the clear-to-send (CTS) pin on TELEM3. Connect the RTS pin on TELEM3 to the CTS pin on TELEM2.

The Serial Receive block on TELEM3 receives attitude data from TELEM2, and the Serial Receive block on TELEM2 receives angular velocity data from TELEM3.

Configure the Hardware Serial Ports

Configure the serial port settings for TELEM2 and TELEM3 to match the hardware and model configurations

To review the serial port mapping for the selected ArduPilot hardware board, on the Modeling tab, click Model Settings. The hardware settings map logical serial ports to physical connectors, such as TELEM1, TELEM2, and TELEM3.
In the Configuration Parameters dialog box, select Hardware Implementation.
Set Hardware board to the ArduPilot controller that you selected during hardware setup.
In the Hardware board settings > Target hardware resources > Serial, set these parameters: Baud rate: 2000000; Parity: Odd; Stop bits: 2.
Save these parameter values for TELEM2 and TELEM3.

These settings align the serial communication parameters on both telemetry ports consistent with the model configuration.

If the model uses hardware flow control, Enable hardware flow control for both ports. Then connect the RTS and CTS pins as described in the loopback wiring section, because the ports use those signals to control data transfer.

Configure Sending and Receiving Angular Velocity and Attitude

Configure the Serial Transmit and Serial Receive blocks so that each telemetry port sends one signal and receives the signal from the opposite port.

Set the Serial Transmit block that transmits attitude data to use TELEM2.
Set the Serial Receive block that receives attitude data to use TELEM3.
Set the Serial Transmit block that transmits angular velocity data to use TELEM3.
Set the Serial Receive block that receives angular velocity data to use TELEM2.
In each Serial Receive block, set Data type and Data length to match the signal from the corresponding Serial Transmit block. For example, if the transmit path sends a 1-by-3 vector of single-precision values, set Data type to single and Data length to 3.

If the Serial Receive and Serial Transmit block requires a logical serial port, select the Select logical serial port check box. Then from the Serial logical port list, select the port.

Matching Data type and Data length enables the Serial Receive block to convert the incoming bytes into the expected signal. If Data type or Data length do not match, the Serial Receive block misinterprets the byte stream and produces incorrect values.

Run and Verify Loopback Communication

To verify that the serial communication path transfers data between the TELEM2 and TELEM3 ports.

Run the model in Monitor & Tune or Connected IO mode on the target hardware. The model transmits attitude data from TELEM2 to the Rx pin on TELEM3 and transmits angular velocity data from TELEM3 to the Rx pin on TELEM2.

To compare the transmitted and received values, use the Display blocks in the model. Matching values confirm that the wiring, serial port configuration, and block parameters are consistent across both communication paths.

If the displayed values do not match, verify the Tx and Rx connections. Then verify that both telemetry ports use the same Baud rate, Parity, Stop-bits, and flow control settings. Also verify that each Serial Receive block uses the same Data type and Data length settings as the signal from the corresponding Serial Transmit block.

After you confirm that the serial blocks exchange matching data, you can reuse the same wiring and port configuration to exchange sensor, telemetry, or command data in your own applications. To extend this workflow to custom frame-based serial communication, see Send and Receive Custom Frame-Based Serial Data with ArduPilot.