//
// Module Name: I2C.c
//
// Description: This module contains the low and high level I2C access routine for the Atmel TWI (I2C) interface (on the mega128).
//
// History:
//	- Created on May 1st 2002 by Stephane Gauthier (email: stephane.gauthier@alcatel.com URL:http://robots.dnsq.org)
//	- May 21st 2002 - S. Gauthier - Modified i2c_readbyte() and i2c_writebyte() to exit cleanly (run i2c_stop, set mutex and re-enable ints).
//	- June 2nd 2002 - S. Gauthier - Cleaned up and added I2C error count var for troubleshooting.
//  - June 25th 2002 - S. Gauthier - Added _SFR_ASM_COMPAT define to prevent warnings with new AVRGCC compiler (3.2)
//


#include <avr/io.h>					// For I/O macros
#include <avr/twi.h>				// AVRGCC TWI include.
#include "I2C.h"					// For our own routines
#include "avrx.h"					// For semaphores
#include "generalio.h"				// for PrintString
#include "serialio.h"				// For error reporting. (PutChar())
#include "hardware.h"				// sets up hardware specifics defines, macros and constants.

#define I2C_ERROR 1

unsigned int i2c_errors;
unsigned int i2c_requests;

// Globals
AVRX_MUTEX(I2C_Mutex);										// For controlling access to I2C hardware.


// **************************
// Low-level I2C routines.
// **************************

// Function Name:   i2c_init()
// 
// Description:   Initializes the I2C hardware
//
//
void i2c_init(void)
{
	// Prime I2C semaphore
	AvrXSetSemaphore(&I2C_Mutex);

	// Configure Bit rate generator for 100Khz
	TWBR = TWBR_INIT;
	
	// Prescaler of 1
	TWSR = TWPS_INIT;
	
	// Enable TWI
	TWCR = TWCR_INIT;
}

// Function Name:   i2c_start()
// 
// Description:   Prepare to take over bus. Return 0 if successfull, otherwise 1.
//
//
unsigned char i2c_start(unsigned char data)
{
	// Initiate Start 
	outp((BV(TWINT) | BV(TWSTA) | BV(TWEN)), TWCR);
	
	// Wait 'till it's done...
	while (bit_is_clear(TWCR, TWINT))
		;

	// check for proper status in TWSR..
	if ((inp(TWSR) & 0xF8) != TW_START)
	{
		return (1);						// BAD!!
	}
	
	// Send SLA_W
	outp(data, TWDR);
	
	// start transmission
	outp((BV(TWINT) | BV(TWEN)), TWCR);
	
	// Wait 'till it's done...
	while (bit_is_clear(TWCR, TWINT))
		;
		
	// check for proper status in TWSR..
	if ((inp(TWSR) & 0xF8) != TW_MT_SLA_ACK)
	{
		return (1);						// BAD!!
	}
	
	// Success
	return (0);
}

// Function Name:   i2c_rep_start()
// 
// Description:   Repeated Start. Switch mode without losing bus. Return 0 if successfull, otherwise 1.
//
//
unsigned char i2c_rep_start(unsigned char data)
{
	// Initiate Start 
	outp((BV(TWINT) | BV(TWSTA) | BV(TWEN)), TWCR);
	
	// Wait 'till it's done...
	while (bit_is_clear(TWCR, TWINT))
		;
	
	// check for proper status in TWSR..
	if ((inp(TWSR) & 0xF8) != TW_REP_START)
	{
		return (1);						// BAD!!
	}
	
	// Send SLA_W or SLA_R
	outp(data, TWDR);
	
	// start transmission
	outp((BV(TWINT) | BV(TWEN)), TWCR);
	
	// Wait 'till it's done...
	while (bit_is_clear(TWCR, TWINT))
		;

	// check for proper status in TWSR..
	if ((inp(TWSR) & 0xF8) != TW_MR_SLA_ACK)	
	{
		return (1);						// BAD!!
	}

	// Success
	return (0);
}

// Function Name:   i2c_stop()
// 
// Description:   Release I2C bus.
//
//
void i2c_stop(void)
{
	// Initiate Stop 
	outp((BV(TWINT) | BV(TWSTO) | BV(TWEN)), TWCR);
}


// Function Name:   i2c_write()
// 
// Description:   Write byte to currently addressed slave
//
//
unsigned char i2c_write(unsigned char data)
{
	// Send Data
	outp(data, TWDR);			// Data
	
	// Start transmission
	outp((BV(TWINT) | BV(TWEN)), TWCR);

	// Wait 'till it's done...
	while (bit_is_clear(TWCR, TWINT))
		;
	
	// check for proper status in TWSR..
	if ((inp(TWSR) & 0xF8) != TW_MT_DATA_ACK)
	{
		return (1);						// BAD!!
	}
	
	// Success
	return (0);
}


// Function Name:   i2c_read()
// 
// Description:   Read byte from currently addressed slave. ack parameter determines if we should slave ack or not.
//
//
unsigned char i2c_read(unsigned char ack)
{
	// Prepare to receive next byte
	if (ack == ACK)
		outp((BV(TWINT) | BV(TWEA) | BV(TWEN)), TWCR);		// Send ACK
	else
		outp((BV(TWINT) | BV(TWEN)), TWCR);					// Send NACK
	
	// Wait 'till it's done...
	while (bit_is_clear(TWCR, TWINT))
		;
		
	// Get Data
	return(inp(TWDR));
}

// **************************
// High-level I2C routines.
// **************************


// Function Name:   i2c_readbyte()
// 
// Description:   Read a single byte from device 'i2c_address' at address 'location'.
//
//
unsigned char i2c_readbyte(unsigned char i2c_address, unsigned char location)
{
	unsigned char temp = 0;
	
	AvrXWaitSemaphore(&I2C_Mutex);

	//i2c_requests++;
	
	// set device address and write mode (exit with error if it fails.)
	if (i2c_start(i2c_address+I2C_WRITE))
	{
		i2c_errors++;
		
#ifdef I2C_ERROR
		PutChar('r');
		PutChar('1');
#endif		
	}
	else
	{
		// write byte address
		if (i2c_write(location))
		{
			i2c_errors++;
			
#ifdef I2C_ERROR
			PutChar('r');
			PutChar('2');
#endif
		}
		else
		{
    		// set device address and read mode
    		if (i2c_rep_start(i2c_address+I2C_READ))   			
    		{
    			i2c_errors++;
    			
#ifdef I2C_ERROR    			
    			PutChar('r');
    			PutChar('3');
#endif    			
    		}
    		else
    			temp = i2c_read(NACK);       						// read one byte only
    	}
	}
	
	i2c_stop();
			
	AvrXSetSemaphore(&I2C_Mutex);

	return(temp);
}


// Function Name:   i2c_writebyte()
// 
// Description:   Write single byte 'data' to device 'i2c_address' at address 'location'. Returns results of operation.
//
//
unsigned char i2c_writebyte(unsigned char i2c_address, unsigned char location, unsigned char data)
{
	unsigned char temp = 0;
	
	AvrXWaitSemaphore(&I2C_Mutex);
	
	//i2c_requests++;
			
	// set device address and write mode
	if (i2c_start(i2c_address+I2C_WRITE))          
	{
		i2c_errors++;

#ifdef I2C_ERROR		
		PutChar('w');
		PutChar('1');
#endif		
	}
	else
	{
		if (i2c_write(location))                		// write location address to write to
		{
			i2c_errors++;
			
#ifdef I2C_ERROR
			PutChar('w');
			PutChar('2');
#endif		
		}
		else
		{
			if ((temp = i2c_write(data)))				// ret=0 -> Ok, ret=1 -> no ACK 
			{
				i2c_errors++;
				
#ifdef I2C_ERROR
				PutChar('w');
				PutChar('3');
#endif
			}
		}
	}
	
	i2c_stop();                          		// set stop conditon = release bus
	
	AvrXSetSemaphore(&I2C_Mutex);
	
	return(temp);
}


// Function Name:   i2c_readword()
// 
// Description:   Read a single word from device 'i2c_address' at address 'location'.
//
//
unsigned int i2c_readword(unsigned char i2c_address, unsigned char location)
{
	
	unsigned int temp = 0;
	
	AvrXWaitSemaphore(&I2C_Mutex);
		
	if (i2c_start(i2c_address+I2C_WRITE))  					// set device address and write mode
	{
		i2c_errors++;
	}
	else
	{
		if (i2c_write(location))          					// write byte address
		{
			i2c_errors++;
		}
		else
		{
			if (i2c_rep_start(i2c_address+I2C_READ))		// set device address and read mode
			{
				i2c_errors++;
			}
			else
			{
				temp = i2c_read(ACK) << 8;							// Get High Byte
				temp += i2c_read(NACK);       						// Get Low Byte
			}
		}
	}
	
	i2c_stop();
	
	AvrXSetSemaphore(&I2C_Mutex);
	
	return(temp);
}


// Function Name:   i2c_writeword()
// 
// Description:   Write single word 'data' to device 'i2c_address' at address 'location'. Returns results of operation.
//
//
unsigned char i2c_writeword(unsigned char i2c_address, unsigned char location, unsigned int data)
{
	
	unsigned char temp=0;
		
	AvrXWaitSemaphore(&I2C_Mutex);
	
	if (i2c_start(i2c_address+I2C_WRITE))           // set device address and write mode
	{
		i2c_errors++;
	}
	else
	{
		if (i2c_write(location))                		// write location address to write to
		{
			i2c_errors++;
		}
		else
		{
			if ((temp = i2c_write((unsigned char)(data >> 8))))				// Write High Byte first
			{
				i2c_errors++;
			}
			else
			{
				if (temp += i2c_write((unsigned char)data))					// Write Low Byte
				{
					i2c_errors++;
				}
			}
		}
	}
	
	i2c_stop();                          		// set stop conditon = release bus
	
	AvrXSetSemaphore(&I2C_Mutex);
	
	return(temp);
}