How to Use UART Serial Port on Raspberry Pi

The UART is one of the most used interfaces for communicating Raspberry Pi with other devices, such as sensors, GPS modules, Bluetooth modules, and other microcontrollers.

UART (Universal Asynchronous Receiver-Transmitter) is a serial communication protocol that allows data transmission between devices asynchronously.

Let’s see how we can use it with a Raspberry Pi 👇

What is UART?

UART is a serial communication protocol that uses two data lines: TX (Transmit) and RX (Receive). These lines allow bidirectional communication between two devices.

UART communication is asynchronous, meaning there is no shared clock signal between devices. Instead, both devices must be configured to use the same transmission speed, known as baud rate.

Unlike other protocols like SPI or I2C, UART does not require a shared clock, making it simpler but also slower in comparison.

UART on Raspberry Pi

The Raspberry Pi has a built-in UART port that can be used to communicate with other devices. On most Raspberry Pi models, the UART is available on the GPIO pins:

Furthermore, the UART on Raspberry Pi can be used for communication with the serial console, which is useful for system debugging and configuration.

Configuring UART on Raspberry Pi

Practical Example

Let’s see how it works with a practical example of how to use UART to communicate a Raspberry Pi with an Arduino.

void setup() {
  Serial.begin(9600); // Initializes UART at 9600 baud
}

void loop() {
  if (Serial.available() > 0) {
    char receivedChar = Serial.read(); // Read a received character
    Serial.print("Received: ");
    Serial.println(receivedChar); // Sends back the received character
  }
}

import serial
import time

# Set up the serial port
ser = serial.Serial('/dev/serial0', 9600, timeout=1)
ser.flush()

try:
    while True:
        # Send a character to the Arduino
        ser.write(b'A')
        print("Sent: A")
        
        # Wait for a response
        if ser.in_waiting > 0:
            line = ser.readline().decode('utf-8').rstrip()
            print(f"Received: {line}")
        
        time.sleep(1)
except KeyboardInterrupt:
    print("Program terminated")
finally:
    ser.close()

Now