Below is the file 'i2c.c' from this revision. You can also download the file.

#include "i2c.h"

#define I2CBASE  0xE001C000

#define I2CONSET 0x00
#define I2STAT   0x04
#define I2DAT    0x08
#define I2ADR    0x0c
#define I2SCLH   0x10
#define I2SCLL   0x14
#define I2CONCLR 0x18

#define IREG(x) (((volatile unsigned char *)I2CBASE)[x])
#define IWREG(x) (((volatile unsigned int *)I2CBASE)[(x)/sizeof(unsigned int)])

#define AAFLAG (1<<2)
#define SIFLAG (1<<3)
#define STOFLAG (1<<4)
#define STAFLAG (1<<5)

#define SI (IREG(I2CONSET) & SIFLAG)

void init_i2c(void)
{
	IREG(I2CONSET) = 0x40; /* Enable I2C ready for Master Tx */
	/* Set up for just under 400kHz */
#if 0
	IWREG(I2SCLL) = (25 * 100);
	IWREG(I2SCLH) = (12 * 100);
#else
# if 0
	IWREG(I2SCLL) = 1475; /* ~5kHz */
	IWREG(I2SCLH) = 1475;
# else
	IWREG(I2SCLL) = 73; /* ~100kHz */
	IWREG(I2SCLH) = 73;
# endif
#endif
}

int i2cstat;

int i2c_wait(void)
{
	int stat;
	while (!SI);
	stat = IREG(I2STAT);
	i2cstat = stat;
	return stat;
}

int i2c_conreg(void)
{
	return IREG(I2CONSET);
}

int i2c_statreg(void)
{
	return IREG(I2STAT);
}

bool i2c_send_start(void)
{
	IREG(I2CONCLR) = STOFLAG | STAFLAG;
	IREG(I2CONSET) = STAFLAG;
	switch (i2c_wait()) {
	case 0x08:
	case 0x10:
		return TRUE;
	default:
		i2c_send_stop();
		return FALSE;
	}
}

bool i2c_send_address(int addr, bool write)
{
	return i2c_send_data((addr<<1) + (write?0:1));
}

bool i2c_send_data(int data)
{
	IREG(I2DAT) = data;
	IREG(I2CONCLR) = STAFLAG | STOFLAG | SIFLAG;
	switch (i2c_wait()) {
	case 0x18:
	case 0x28:
	case 0x40:
		return TRUE;
	default:
		i2c_send_stop();
		return FALSE;
	}
}

bool i2c_receive_data(int *data, bool last)
{
	if (!last)
		IREG(I2CONSET) = AAFLAG;
	IREG(I2CONCLR) = STAFLAG | STOFLAG | SIFLAG | (last?AAFLAG:0);
	switch (i2c_wait()) {
	case 0x50:
	case 0x58:
		*data = IREG(I2DAT);
		return TRUE;
	default:
		i2c_send_stop();
		return FALSE;
	}
}

void i2c_send_stop(void)
{
	IREG(I2CONCLR) = STAFLAG | AAFLAG;
	IREG(I2CONSET) = STOFLAG;
	IREG(I2CONCLR) = SIFLAG;
	/* Don't think we need to wait here. Could be wrong. */
}