This tutorial explains how to enable and customize S.BUS control on the ESP32-based driver board.

After completing these steps, your RC transmitter can directly control the robot through the S.BUS receiver connected to the board.

1. Enable S.BUS Mode

Open the project and edit the Config.h file.

Add the following line to enable S.BUS on UART0 (default baud rate: 1 Mbps):

#define UART0_AS_SBUS

Once enabled, UART0 will automatically act as the S.BUS input interface.

2. Modify the Example Code

In main.cpp, locate the loop() function.

You’ll find an example S.BUS routine that reads RC channel values and converts them into motor control commands.

You can adjust this section to fit your transmitter’s channel mapping and value range.

Example snippet:

#ifdef UART0_AS_SBUS
  if (sbus.Read()) {
    sbusData = sbus.data();

    // Print received channel data
    for (int8_t i = 0; i < sbusData.NUM_CH; i++) {
      Serial.print(sbusData.ch[i]);
      Serial.print("\\t");
    }
    Serial.print(sbusData.lost_frame);
    Serial.print("\\t");
    Serial.println(sbusData.failsafe);

    // Define speed scaling based on CH5 (mode switch)
    float speed_limit = 1.0;
    if (sbusData.ch[4] < 300) {
      speed_limit = 0.33;
    } else if (sbusData.ch[4] == 1002) {
      speed_limit = 0.66;
    } else if (sbusData.ch[4] > 1700) {
      speed_limit = 1.0;
    }

    // Convert joystick input to differential drive commands
    float speed_input = constrain(float(sbusData.ch[2] - SBUS_MID)/SBUS_RAN, -1.0, 1.0);
    float turn_input  = -constrain(float(sbusData.ch[3] - SBUS_MID)/SBUS_RAN, -1.0, 1.0);

    float left_speed  =  (speed_input) * speed_limit * 6000.0 - (turn_input * 0.33 * 6000.0);
    float right_speed =  (speed_input) * speed_limit * 6000.0 + (turn_input * 0.33 * 6000.0);

    jointsCtrl.hubMotorCtrl(left_speed, right_speed, right_speed, left_speed);
  }
#endif

After making changes, build and flash the firmware to the driver board.

3. Hardware Connection

Connect your RC receiver to the driver board as follows: