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Two Projects Communication

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Summary

This week, I worked on implementing I2C communication between two microcontrollers: a RP2040 (acting as the master) and an ESP32 (acting as the slave).

I configured the I2C communication, where the RP2040 sends messages to the ESP32, which processes the data and forwards it to another RP2040. Additionally, I integrated WiFi communication between the ESP32 units to enable communication over a network, allowing one ESP32 to receive data from the RP2040 via I2C, then transmit it over WiFi to another RP2040.

Throughout this process, I had to troubleshoot issues such as incorrect data type conversions, especially with Wire.write(), and used proper data formatting to ensure the communication worked correctly.

The group assignment Page :

Work Process Detail

RP2040_1 --(I2C)--> ESP32_1 --(WiFi)--> ESP32_2 --(I2C)--> RP2040_2

Concept

  • RP2040_1 (Master) → sends a message to ESP32_1 (Slave) over I2C
  • ESP32_1 (WiFi Client) → sends that message over WiFi to ESP32_2 (WiFi Server)
  • ESP32_2 (Master) → sends that message to RP2040_2 (Slave) over I2C

This is 100% possible 👍

Simple Flow

StepAction
1RP2040_1 sends text via I2C to ESP32_1
2ESP32_1 connects over WiFi to ESP32_2 and sends message
3ESP32_2 receives WiFi message and sends it via I2C to RP2040_2
4RP2040_2 receives message and prints it

Programming Hints

🟢 RP2040_1 (I2C Master)

Use Wire.h library to send a string to ESP32_1.

#include <Wire.h>
void setup() {
  Wire.begin();
}
void loop() {
	const char* message = "Hello FAB25!";
  Wire.beginTransmission(0x08);  // Address of ESP32_1
  Wire.write((const uint8_t*)message , strlen(message ));
  Wire.endTransmission();
  delay(5000);
}

🟢 ESP32_1 (I2C Slave + WiFi Client)

Use Wire.onReceive() to get data from RP2040_1, then send via WiFi to ESP32_2.

#include <WiFi.h>
#include <Wire.h>

String i2cMessage = "";

void receiveI2C(int bytes) {
  while (Wire.available()) {
    i2cMessage += (char)Wire.read();
  }
}

void setup() {
  Wire.begin(0x08);       // I2C Slave address
  Wire.onReceive(receiveI2C);

  WiFi.begin("ESP32_SERVER", "12345678");
  while (WiFi.status() != WL_CONNECTED) delay(500);
}

void loop() {
  if (i2cMessage.length() > 0) {
    WiFiClient client;
    if (client.connect("192.168.4.1", 80)) {
      client.println(i2cMessage);
      client.stop();
      i2cMessage = "";  // Reset
    }
  }

🟢 ESP32_2 (WiFi Server + I2C Master)

Receive message over WiFi and send via I2C to RP2040_2.

#include <WiFi.h>
#include <Wire.h>

WiFiServer server(80);

void setup() {
  Wire.begin();
  WiFi.softAP("ESP32_SERVER", "12345678");
  server.begin();
}

void loop() {
  WiFiClient client = server.available();
  if (client) {
    String data = client.readStringUntil('\n');
    Wire.beginTransmission(0x09); // Address of RP2040_2
    Wire.write((const uint8_t*)data.c_str(), data.length());
    Wire.endTransmission();
    client.stop();
  }

🟢 RP2040_2 (I2C Slave)

Just print the received message.

#include <Wire.h>

void receiveI2C(int bytes) {
  while (Wire.available()) {
    char c = Wire.read();
    Serial.print(c);
  }
}

void setup() {
  Serial.begin(115200);
  Wire.begin(0x09);        // I2C Slave address
  Wire.onReceive(receiveI2C);
}

void loop() {
  delay(100);
}

Learning Outcome

  • I2C Communication Setup: Learned how to establish I2C communication between different microcontrollers (RP2040 & ESP32).
  • Data Type Management: Gained experience handling data type conversions between different microcontrollers and communication protocols.
  • WiFi Integration: Expanded knowledge of WiFi-based communication between devices and how it complements I2C.
  • Debugging: Improved debugging skills when addressing issues related to data transfer and compatibility between devices.
  • Practical Use of Communication Protocols: Deepened understanding of serial communication protocols (I2C & WiFi) in embedded systems and their integration for more complex setups.

Digital Files