I2C Example

I2C_Exmaple.ino

#include "Arduino.h"
#include <Wire.h>
// The code is inspired by the example given at http://dsscircuits.com/articles/arduino-i2c-slave-guide
 

/*
 * Set right motor speed
 * i2cset -y 1 0x29 0x04 501 w
 * Set left motor speed
 * i2cset -y 1 0x29 0x03 501 w
 * Get left sensor
 * i2cget -y 1 0x29 0 w
 * $0x0400
 * Get right sensor
 * i2cget -y 1 0x29 2 w
 * $0x012d
 * */

/********************************************************************/

#define  SLAVE_ADDRESS           0x29  //slave address,any number from 0x01 to 0x7F
#define  REG_MAP_SIZE            5
#define  MAX_SENT_BYTES          3
#define  IDENTIFICATION          0x0D

#define LEFT_SENSOR_ADDRESS 0
#define RIGHT_SENSOR_ADDRESS 2
#define LEFT_MOTOR_ADDRESS 3
#define RIGHT_MOTOR_ADDRESS 4
void storeData();

/********* Global  Variables  ***********/
byte registerMap[REG_MAP_SIZE];
byte registerMapTemp[REG_MAP_SIZE];
byte receivedCommands[MAX_SENT_BYTES];
byte newDataAvailable = 0;

//on arduino uno this is 2 bytes
int leftMotorSpeed = 1;
int rightMotorSpeed = 2;
int rightSensor = 301;
int leftSensor = 1024;

void setup() {
	Serial.begin(9600);
	Wire.begin(SLAVE_ADDRESS);
	Wire.onRequest(requestEvent);
	Wire.onReceive(receiveEvent);
	registerMap[13] = IDENTIFICATION; // ID register
}

void loop() {
	storeData();
	newDataAvailable = 1;
}

void storeInt(byte startIndex, int* ptr) {
	byte arrayIndex = startIndex;
	byte * bytePointer = (byte*) ptr; //latitude is 4 bytes
	for (int i = 0; i < 2; i++) {
		registerMapTemp[arrayIndex] = bytePointer[i]; //increment pointer to store each byte
		arrayIndex++;
	}
}

void reStoreInt(byte address, int* ptr) {

	int tmp = receivedCommands[1];
	tmp += (receivedCommands[1 + 1] << 8);
	*ptr = tmp;
	char buffer[200];
	sprintf(buffer, "Setting address %d = %d", address, *ptr);
	Serial.println(buffer);
}

void storeData() {

	storeInt(0, &leftSensor);
	storeInt(2, &rightSensor);
}

void requestEvent() {
	if (newDataAvailable) {
		for (int c = 0; c < (REG_MAP_SIZE - 1); c++) {
			registerMap[c] = registerMapTemp[c];
		}
	}

	newDataAvailable = 0;

	//Set the buffer to send all 14 bytes
	Wire.write(registerMap + receivedCommands[0], REG_MAP_SIZE);
}

void receiveEvent(int bytesReceived) {
	for (int a = 0; a < bytesReceived; a++) {
		if (a < MAX_SENT_BYTES) {
			receivedCommands[a] = Wire.read();
		} else {
			Wire.read(); // if we receive more data then allowed just throw it away
		}
	}

	if (bytesReceived == 1 && (receivedCommands[0] < REG_MAP_SIZE)) {
		return;
	}

	if (bytesReceived == 1 && (receivedCommands[0] >= REG_MAP_SIZE)) {
		receivedCommands[0] = 0x00;
		return;
	}

	switch (receivedCommands[0]) {
	case RIGHT_MOTOR_ADDRESS:
		reStoreInt(receivedCommands[0], &leftMotorSpeed);
		return;
	case LEFT_MOTOR_ADDRESS:
		reStoreInt(receivedCommands[0], &rightMotorSpeed);
		return;
	default:
		return; // ignore the commands and return
	}

}

RaspberryPiSetup.md

http://radiostud.io/howto-i2c-communication-rpi/

1. Enable I2C using sudo raspi-config
2. Reboot
3. Use i2c[detect|set|get] or
4. Install sudo apt-get install python-smbus python3-smbus python-dev python3-dev
5. Install sudo apt-get install i2c-tools
6. Checkout python example git clone https://github.com/suryasundarraj/rpi-series.git