/*************************************************************************
* Title:    I2C master library using hardware TWI interface
* Author:   Peter Fleury <pfleury@gmx.ch>  http://jump.to/fleury
* File:     $Id: twimaster.c,v 1.3 2005/07/02 11:14:21 Peter Exp $
* Software: AVR-GCC 3.4.3 / avr-libc 1.2.3
* Target:   any AVR device with hardware TWI 
* Usage:    API compatible with I2C Software Library i2cmaster.h
**************************************************************************/

// In order to work around strange bugs in the arduino software, this library
// has been wrapped in a simple i2cmaster class. Modification performed by
// Matthew Beckler and Adam Wolf of Wayne and Layne, LLC, for their 
// Video Game Shield project:
// http://www.wayneandlayne.com/projects/video-game-shield/

#ifndef I2CMASTER_C
#define I2CMASTER_C

#include <inttypes.h>
#include <compat/twi.h>

#if defined(ARDUINO) && ARDUINO >= 100
#include "Arduino.h"
#else
#include "WProgram.h"
#endif

#include "i2cmaster.h"


/* define CPU frequency in Mhz here if not defined in Makefile */
#ifndef F_CPU
#define F_CPU 1600000UL
#endif

/* I2C clock in Hz */
#define SCL_CLOCK  100000L

/*************************************************************************
 Initialization of the I2C bus interface. Need to be called only once
*************************************************************************/
void i2cmaster::i2c_init(void)
{
  /* initialize TWI clock: 100 kHz clock, TWPS = 0 => prescaler = 1 */
  
  TWSR = 0;                         /* no prescaler */
  TWBR = ((F_CPU/SCL_CLOCK)-16)/2;  /* must be > 10 for stable operation */

  // This line added by Matthew Beckler (Wayne and Layne, LLC) to work with
  // designs that don't have external pullup resistors. This command turns on
  // the internal pullups. Might not work if you have large or long wires for
  // SDA and SCL, or if you have many devices on the bus. Works just fine with
  // a 24LC256 EEPROM on a pcb with the atmega328p.
  PORTC |= _BV(4) | _BV(5);
}/* i2c_init */


/*************************************************************************	
  Issues a start condition and sends address and transfer direction.
  return 0 = device accessible, 1= failed to access device
*************************************************************************/
unsigned char i2cmaster::i2c_start(unsigned char address)
{
    uint8_t   twst;

    // send START condition
    TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN);

    // wait until transmission completed
    while(!(TWCR & (1<<TWINT)));

    // check value of TWI Status Register. Mask prescaler bits.
    twst = TW_STATUS & 0xF8;
    if ( (twst != TW_START) && (twst != TW_REP_START)) return 1;

    // send device address
    TWDR = address;
    TWCR = (1<<TWINT) | (1<<TWEN);

    // wail until transmission completed and ACK/NACK has been received
    while(!(TWCR & (1<<TWINT)));

    // check value of TWI Status Register. Mask prescaler bits.
    twst = TW_STATUS & 0xF8;
    if ( (twst != TW_MT_SLA_ACK) && (twst != TW_MR_SLA_ACK) ) return 1;

    return 0;

}/* i2c_start */


/*************************************************************************
 Issues a start condition and sends address and transfer direction.
 If device is busy, use ack polling to wait until device is ready

 Provide the timeout you want in timeout_ms.
 Returns:
    0 device accessible
    1 timeout
 
 Input:   address and transfer direction of I2C device, timeout_ms
*************************************************************************/
unsigned char i2cmaster::i2c_start_wait(unsigned char address, unsigned int timeout_ms)
{
    uint8_t   twst;

    unsigned long end_time = millis() + timeout_ms;

    while ( millis() < end_time )
    {
        // send START condition
        TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN);
    
    	// wait until transmission completed
    	while(!(TWCR & (1<<TWINT)));
    
    	// check value of TWI Status Register. Mask prescaler bits.
    	twst = TW_STATUS & 0xF8;
    	if ( (twst != TW_START) && (twst != TW_REP_START)) continue;
    
    	// send device address
    	TWDR = address;
    	TWCR = (1<<TWINT) | (1<<TWEN);
    
    	// wail until transmission completed
    	while(!(TWCR & (1<<TWINT)));
    
    	// check value of TWI Status Register. Mask prescaler bits.
    	twst = TW_STATUS & 0xF8;
    	if ( (twst == TW_MT_SLA_NACK )||(twst ==TW_MR_DATA_NACK) ) 
    	{    	    
    	    /* device busy, send stop condition to terminate write operation */
            TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);
            
            // wait until stop condition is executed and bus released
            while(TWCR & (1<<TWSTO));

    	    continue;
    	}
	        
    	//if( twst != TW_MT_SLA_ACK) return 1;
    	return 0;
    }
    return 1;

}/* i2c_start_wait */


/*************************************************************************
 Issues a repeated start condition and sends address and transfer direction 

 Input:   address and transfer direction of I2C device
 
 Return:  0 device accessible
          1 failed to access device
*************************************************************************/
unsigned char i2cmaster::i2c_rep_start(unsigned char address)
{
    return i2c_start( address );

}/* i2c_rep_start */


/*************************************************************************
 Terminates the data transfer and releases the I2C bus
*************************************************************************/
void i2cmaster::i2c_stop(void)
{
    /* send stop condition */
	TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);
	
	// wait until stop condition is executed and bus released
	while(TWCR & (1<<TWSTO));

}/* i2c_stop */


/*************************************************************************
  Send one byte to I2C device
  
  Input:    byte to be transfered
  Return:   0 write successful 
            1 write failed
*************************************************************************/
unsigned char i2cmaster::i2c_write( unsigned char data )
{	
    uint8_t   twst;
    
	// send data to the previously addressed device
	TWDR = data;
	TWCR = (1<<TWINT) | (1<<TWEN);

	// wait until transmission completed
	while(!(TWCR & (1<<TWINT)));

	// check value of TWI Status Register. Mask prescaler bits
	twst = TW_STATUS & 0xF8;
	if( twst != TW_MT_DATA_ACK) return 1;
	return 0;

}/* i2c_write */


/*************************************************************************
 Read one byte from the I2C device, request more data from device 
 
 Return:  byte read from I2C device
*************************************************************************/
unsigned char i2cmaster::i2c_readAck(void)
{
	TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWEA);
	while(!(TWCR & (1<<TWINT)));    

    return TWDR;

}/* i2c_readAck */


/*************************************************************************
 Read one byte from the I2C device, read is followed by a stop condition 
 
 Return:  byte read from I2C device
*************************************************************************/
unsigned char i2cmaster::i2c_readNak(void)
{
	TWCR = (1<<TWINT) | (1<<TWEN);
	while(!(TWCR & (1<<TWINT)));
	
    return TWDR;

}/* i2c_readNak */

#endif