Group Assignment: Networking and Communication
For this week's group assignment we had to send a message between two projects.
I²C
I²C is a serial protocol for two-wire interface to connect low-speed devices like microcontrollers, EEPROMs, A/D and D/A converters, I/O interfaces and other similar peripherals in embedded systems. The I²C bus is a very popular and powerful bus used for communication between a master (or multiple masters) and a single or multiple slave devices. Each I²Cslave device needs an address. I²C uses only two wires: SCL (serial clock) and SDA (serial data).
Programming Master/Slave
We have developed a small interpreter that switches the LEDs on and off. For example, if you enter 00, the LEDs on both boards would turn off and if you enter 11, the LEDs on both microcontroller boards would light up. We used I²C to transfer the values. We connected the board from Hakan Zayin and Alessandra Crotty to demonstrate it.
Master Code
#include <Wire.h>
#define LEDPin 5 // define the LED pin
String bsend;
void setup() {
Wire.begin(); // join i2c bus (address optional for master)
Serial.begin(9600); //here we decalre Serial at 9600 baudrate for the input
pinMode(LEDPin,OUTPUT);// set LED pin as an output
}
void loop() {
if (Serial.available() > 0) // If we have some input
{
bsend = Serial.readString(); // we read it as String
/*
So one thing I have to mention here, we have write a BIN input(4bit)
*/
Serial.println(bsend); // debugging
send(bsend); // call the send(input) function
}
}
void send(String input){
if(input.charAt(0) == '1'){ // okay here we check the character on 2 places (master and slave)
Wire.beginTransmission(11); // transmit to device (slave)
Wire.write(1); // sends 1
Wire.endTransmission(); // stop transmitting
}else if(input.charAt(0) == '0' ){ //if it's 0, transmit 0
Wire.beginTransmission(11); // transmit to device (slave)
Wire.write(0); // sends 0
Wire.endTransmission(); // stop transmitting
}
//---------------------------------------------------------------
if(input.charAt(1) == '1'){ // Master board turn on or off LED
digitalWrite(LEDPin,HIGH);
}else if(input.charAt(1) == '0' ){
digitalWrite(LEDPin,LOW);
}
}
Slave Code
#include <Wire.h>
#define LEDPin 5 // again define the LED on pin 5
void setup() {
// put your setup code here, to run once:
Wire.begin(11); /* join i2c bus with address 13, if you see to the code on the top, we have defined 3 divices
with 11 as S1, 12 as S2 and 13 as S3. So you have to change this value according to the device */
Wire.onReceive(receiveEvent); // register event
pinMode(LEDPin,OUTPUT); // set LED pin as an output
Serial.begin(9600); //for debugging
Serial.println("init");//for debugging
}
void loop() {
delay(100);// we have to assign the delay, so that we can hear work with the input
}
void receiveEvent(int howMany) {
if (Wire.available()) { // the same thing as in serial
byte c = Wire.read(); // receive byte as a character
Serial.println(c); // debug
if (c == 1){ // if the character equals to 1
digitalWrite(LEDPin,HIGH); // turn on the led
}else if(c == 0){ // els if the character equals to 0
digitalWrite(LEDPin,LOW); // turn the led off
}
}
}