Master Slave I2C Connection

How to Set up a MASTER-SLAVE connection between two Arduinos using I2C (Inter-Integrated Circuit) protocol.

Dec 7, 2017

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communication

Components and supplies

Arduino UNO

Jumper wires (generic)

Arduino UNO

Apps and platforms

Arduino IDE

Project description

Code

SLAVE_CODE

c_cpp

Upload to SLAVE Arduino.

1// Include the required Wire library for I2C
2#include <Wire.h>
3int   LED = 13;
4int x = 0;
5void setup() {
6  // Define the LED pin as Output
7   pinMode (LED, OUTPUT);
8  // Start the I2C Bus as Slave on address 9
9  Wire.begin(9);   
10  // Attach a function to trigger when something is received.
11  Wire.onReceive(receiveEvent);
12}
13void   receiveEvent(int bytes) {
14  x = Wire.read();    // read one character from the   I2C
15}
16void loop() {
17  //If value received is 0 blink LED for 200 ms
18   if (x == 0) {
19    digitalWrite(LED, HIGH);
20    delay(200);
21    digitalWrite(LED,   LOW);
22    delay(200);
23  }
24  //If value received is 3 blink LED for 400   ms
25  if (x == 3) {
26    digitalWrite(LED, HIGH);
27    delay(400);
28    digitalWrite(LED,   LOW);
29    delay(400);
30  }
31}
32

// Include the required Wire library for I2C
#include <Wire.h>
int   LED = 13;
int x = 0;
void setup() {
  // Define the LED pin as Output
   pinMode (LED, OUTPUT);
  // Start the I2C Bus as Slave on address 9
  Wire.begin(9);   
  // Attach a function to trigger when something is received.
  Wire.onReceive(receiveEvent);
}
void   receiveEvent(int bytes) {
  x = Wire.read();    // read one character from the   I2C
}
void loop() {
  //If value received is 0 blink LED for 200 ms
   if (x == 0) {
    digitalWrite(LED, HIGH);
    delay(200);
    digitalWrite(LED,   LOW);
    delay(200);
  }
  //If value received is 3 blink LED for 400   ms
  if (x == 3) {
    digitalWrite(LED, HIGH);
    delay(400);
    digitalWrite(LED,   LOW);
    delay(400);
  }
}

MASTER_CODE

c_cpp

Upload to MASTER Arduino.

1// Include the required Wire library for I2C<br>
2#include<Wire.h>
3int  x = 0;
4void setup() {
5  // Start the I2C Bus as Master
6  Wire.begin();  
7}
8void loop() {
9  Wire.beginTransmission(9); // transmit to device #9
10  Wire.write(x);              // sends x 
11  Wire.endTransmission();    // stop  transmitting
12  x++; // Increment x
13  if (x > 5) x = 0; // `reset x once it  gets 6
14  delay(500);
15}
16

// Include the required Wire library for I2C<br>
#include<Wire.h>
int  x = 0;
void setup() {
  // Start the I2C Bus as Master
  Wire.begin();  
}
void loop() {
  Wire.beginTransmission(9); // transmit to device #9
  Wire.write(x);              // sends x 
  Wire.endTransmission();    // stop  transmitting
  x++; // Increment x
  if (x > 5) x = 0; // `reset x once it  gets 6
  delay(500);
}

SLAVE_CODE

c_cpp

Upload to SLAVE Arduino.

1// Include the required Wire library for I2C
2#include <Wire.h>
3int  LED = 13;
4int x = 0;
5void setup() {
6  // Define the LED pin as Output
7  pinMode (LED, OUTPUT);
8  // Start the I2C Bus as Slave on address 9
9  Wire.begin(9);  
10  // Attach a function to trigger when something is received.
11  Wire.onReceive(receiveEvent);
12}
13void  receiveEvent(int bytes) {
14  x = Wire.read();    // read one character from the  I2C
15}
16void loop() {
17  //If value received is 0 blink LED for 200 ms
18  if (x == 0) {
19    digitalWrite(LED, HIGH);
20    delay(200);
21    digitalWrite(LED,  LOW);
22    delay(200);
23  }
24  //If value received is 3 blink LED for 400  ms
25  if (x == 3) {
26    digitalWrite(LED, HIGH);
27    delay(400);
28    digitalWrite(LED,  LOW);
29    delay(400);
30  }
31}
32

// Include the required Wire library for I2C
#include <Wire.h>
int  LED = 13;
int x = 0;
void setup() {
  // Define the LED pin as Output
  pinMode (LED, OUTPUT);
  // Start the I2C Bus as Slave on address 9
  Wire.begin(9);  
  // Attach a function to trigger when something is received.
  Wire.onReceive(receiveEvent);
}
void  receiveEvent(int bytes) {
  x = Wire.read();    // read one character from the  I2C
}
void loop() {
  //If value received is 0 blink LED for 200 ms
  if (x == 0) {
    digitalWrite(LED, HIGH);
    delay(200);
    digitalWrite(LED,  LOW);
    delay(200);
  }
  //If value received is 3 blink LED for 400  ms
  if (x == 3) {
    digitalWrite(LED, HIGH);
    delay(400);
    digitalWrite(LED,  LOW);
    delay(400);
  }
}

Downloadable files

CIRCUIT_DIAG

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