Microcontroller Experiments: Custom Protocol Communication

Introduction

This tutorial covers how to establish custom protocol communication between two microcontrollers. This method can be useful for optimizing specific data transfers in your projects.

Requirements

• Two microcontrollers (e.g., Arduino, ESP32, STM32, etc.)
• Serial communication interface (UART, I2C, SPI)
• Jumper wires
• Power supply

Steps for Implementation

1. Choose Communication Medium

Select UART, I2C, or SPI for communication between the microcontrollers.

2. Designing the Protocol

In a custom protocol, define the message structure, commands, data payload, and checksum.

            [START_BYTE][COMMAND][DATA_LENGTH][DATA_PAYLOAD][CHECKSUM][END_BYTE]
        

3. Master Microcontroller Code Example

        void setup() {
            Serial.begin(9600);
        }

        void loop() {
            byte startByte = 0xAA;
            byte command = 0x01;
            byte dataLength = 1;
            byte dataPayload = 42;
            byte checksum = (startByte + command + dataLength + dataPayload) % 256;
            byte endByte = 0xFF;

            Serial.write(startByte);
            Serial.write(command);
            Serial.write(dataLength);
            Serial.write(dataPayload);
            Serial.write(checksum);
            Serial.write(endByte);

            delay(1000);
        }
        

4. Slave Microcontroller Code Example

        void setup() {
            Serial.begin(9600);
        }

        void loop() {
            if (Serial.available() >= 6) {
                byte startByte = Serial.read();
                if (startByte == 0xAA) {
                    byte command = Serial.read();
                    byte dataLength = Serial.read();
                    byte dataPayload = Serial.read();
                    byte checksum = Serial.read();
                    byte endByte = Serial.read();

                    byte calcChecksum = (startByte + command + dataLength + dataPayload) % 256;

                    if (endByte == 0xFF && checksum == calcChecksum) {
                        Serial.println("Received valid data: " + String(dataPayload));
                    } else {
                        Serial.println("Checksum error");
                    }
                }
            }
        }
        

Explanation

The master microcontroller sends a custom message every second. The slave receives it, checks the checksum for validity, and prints the received data. This simple protocol ensures reliable communication between the two microcontrollers.