Example Code for Arduino-RS485 Communication

Hardware Preparation

Software Preparation

• Development Tool: Arduino IDE (version 1.8.x or 2.x)
• Download Link: Arduino IDE
• Library Loading: No additional libraries are required for this project.

Wiring Diagram

1. Mount the DFR0088 IO expansion shield onto the Arduino board.
2. Connect the A terminal of the DFR0088 RS485 screw terminal to the A terminal of the other RS485 device.
3. Connect the B terminal of the DFR0088 RS485 screw terminal to the B terminal of the other RS485 device.
4. Ensure the power supply for both devices is stable (5V for Arduino).

Other Preparation Work

1. Set the three jumpers on the DFR0088 shield to 485 mode to enable RS485 communication.
2. Open the Arduino IDE and select the correct board (e.g., Arduino UNO) and port in the Tools menu.
3. Set the serial monitor baud rate to 19200 (matching the code).

Sample Code

RS485 Transmit Data

int EN = 2; //RS485 has a enable/disable pin to transmit or receive data. Arduino Digital Pin 2 = Rx/Tx 'Enable'; High to Transmit, Low to Receive

void setup()
{
  pinMode(EN, OUTPUT);
  Serial.begin(19200);
}

void loop()
{
// send data
  digitalWrite(EN, HIGH);//Enable data transmit
  Serial.print('A');
  delay(1000);
}

RS485 Receiving Data

int ledPin = 13;
int EN = 2;
int val;

void setup()
{
  pinMode(ledPin, OUTPUT);
  pinMode(EN, OUTPUT);
  Serial.begin(19200);
}

void loop()
{
  // receive data
 digitalWrite(EN, LOW);//Enable Receiving Data
 val = Serial.read();
  if (-1 != val) {
    if ('A' == val) {
      digitalWrite(ledPin, HIGH);
      delay(500);
      digitalWrite(ledPin, LOW);
      delay(500);
    }
 }
}

Result

• RS485 Transmit Data: The Arduino sends the character A via RS485 every 1 second. Use a serial monitor on the receiving device to verify the data.
• RS485 Receiving Data: When the character A is received, the Arduino’s built-in LED (pin 13) blinks once (on for 500ms, off for 500ms).