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Rs 485 - Troubleshooting

This page contains some tips in case you are having problems using this product.

Check wiring​

Ensure that the RS-485 breakout board is correctly wired to the Dasduino CONNECTPLUS:

  • D (Driver Input) on the RS-485 breakout board should connect to TX on the Dasduino.
  • R (Receiver Output) on the RS-485 breakout board should connect to RX on the Dasduino.
  • DE (Driver Enable) should connect to a GPIO pin (e.g., GPIO 12) on the Dasduino and be set HIGH during transmission.
  • NRE (Receiver Enable) should connect to a GPIO pin (e.g., GPIO 11) on the Dasduino and be set LOW during reception.
  • Ensure that A and B lines are properly connected between both RS-485 breakout boards.

Verify baud rate​

Both devices must use the same baud rate. If you’re using 115200, ensure that both the sender and receiver are configured with this value in their code.

Check common ground​

Both devices must share a common ground. Ensure that the GND pin of the RS-485 breakout board is connected to the GND pin of the Dasduino.

Test with a loopback​

To verify if each RS-485 breakout board is functioning:

  1. Connect A to B directly on the same breakout board.
  2. Send data from the Dasduino and check if it echoes back correctly.

Termination Resistor Configuration​

Ensure JP2 is correctly configured:

  • Close JP2 if your RS-485 breakout board is at one end of the bus.
  • Leave JP2 open if your breakout board is not at an endpoint.

Try running our examples​

If you’re confident that your wiring and configuration are correct, try running our RS-485 Communication Example.

Trim received data​

RS-485 communication often appends extra characters like spaces or newline characters (\n). Use .trim() in your code to clean up received strings before processing them.

Verify TX/RX connections​

  • The sender’s TX pin is connected to the receiver’s D (Driver Input).
  • The receiver’s RX pin is connected to the sender’s R (Receiver Output).

Check DE/NRE logic​

  • The sender sets DE HIGH during transmission.
  • The receiver sets NRE LOW during reception.

Check voltage levels​

Ensure that both devices are powered correctly:

  • The RS-485 breakout board should be powered with 5V from the Dasduino.
  • Ensure that there is no voltage mismatch between devices.

Debug with Serial Monitor​

Add debugging messages Serial.println() in your code to confirm whether data is being sent or received correctly.

Test LED circuit​

Manually test the LED by connecting it directly to 5V and GND through a resistor. If it doesn’t light up, there may be an issue with your LED or wiring.

Verify GPIO output​

Use a simple sketch to toggle the GPIO pin controlling the LED:

void setup() {
  pinMode(33, OUTPUT);
}

void loop() {
  digitalWrite(33, HIGH); // Turn on LED
  delay(1000);
  digitalWrite(33, LOW);  // Turn off LED
  delay(1000);
}