myi2c.c

#include <myi2c.h>

void I2C_Init()
// port mac dinh SCL va SDA cua atmega
// at 16 MHz, the SCL frequency will be 16/(16+2(TWBR)), assuming prescalar of 0.
// so for 100KHz SCL, TWBR = ((F_CPU/F_SCL)-16)/2 = ((16/0.1)-16)/2 = 144/2 = 72.
{
    TWSR = 0; // set prescalar to zero
    TWBR = ((F_CPU / F_SCL) - 16) / 2; // set SCL frequency in TWI bit register
}

byte I2C_Detect(byte addr)
// look for device at specified address; return 1=found, 0=not found
{
    TWCR = TW_START; // send start condition
    while (!TW_READY); // wait
    TWDR = addr; // load device's bus address
    TWCR = TW_SEND; // and send it
    while (!TW_READY); // wait
    return (TW_STATUS == 0x18); // return 1 if found; 0 otherwise
}

byte I2C_FindDevice(byte start)
// returns with address of first device found; 0=not found
{
    byte addr;
    for ( addr = start; addr < 0xFF; addr++) // search all 256 addresses
    {
        if (I2C_Detect(addr)) // I2C detected?
            return addr; // leave as soon as one is found
    }
    return 0; // none detected, so return 0.
}

void I2C_Start(byte slaveAddr) {
    I2C_Detect(slaveAddr);
}

byte I2C_Write(byte data) // sends a data byte to slave
{
    TWDR = data; // load data to be sent
    TWCR = TW_SEND; // and send it
    while (!TW_READY); // wait
    return (TW_STATUS != 0x28);
}

byte I2C_ReadACK() // reads a data byte from slave
{
    TWCR = TW_ACK; // ack = will read more data
    while (!TW_READY); // wait
    return TWDR;
    //return (TW_STATUS!=0x28);
}

byte I2C_ReadNACK() // reads a data byte from slave
{
    TWCR = TW_NACK; // nack = not reading more data
    while (!TW_READY); // wait
    return TWDR;
    //return (TW_STATUS!=0x28);
}

void I2C_WriteByte(byte busAddr, byte data) {
    I2C_Start(busAddr); // send bus address
    I2C_Write(data); // then send the data byte
    I2C_Stop();
}

void I2C_WriteRegister(byte busAddr, byte deviceRegister, byte data) {
    I2C_Start(busAddr); // send bus address
    I2C_Write(deviceRegister); // first byte = device register address
    I2C_Write(data); // second byte = data for device register
    I2C_Stop();
}

byte I2C_ReadRegister(byte busAddr, byte deviceRegister) {
    byte data = 0;
    I2C_Start(busAddr); // send device address
    I2C_Write(deviceRegister); // set register pointer
    I2C_Start(busAddr + READ); // restart as a read operation
    data = I2C_ReadNACK(); // read the register data
    I2C_Stop(); // stop
    return data;
}