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

#include "i2c.h"
#include "interrupt.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 __attribute__((interrupt("IRQ"))) i2c_interrupt_handler(void);

struct i2c_transaction *i2c_transaction;
int i2c_bytes;

void init_i2c(void)
{
	IREG(I2CONSET) = 0x40; /* Enable I2C ready for Master Tx */
	/* Set up for just under 400kHz */
#ifdef I2C_FAST
	IWREG(I2SCLL) = (25 * 100);
	IWREG(I2SCLH) = (12 * 100);
#else
	IWREG(I2SCLL) = 73; /* ~100kHz */
	IWREG(I2SCLH) = 73;
#endif
	interrupt_register(I2C0, i2c_interrupt_handler);
}

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

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

bool i2c_busy(void)
{
	return i2c_transaction != NULL;
}

bool i2c_start_transaction(struct i2c_transaction *t)
{
	if (i2c_transaction)
		return FALSE;

	i2c_transaction = t;
	*(t->result) = I2C_IN_PROGRESS;

	/* Paranoia in case we left things in a bad state */
	IREG(I2CONCLR) = STOFLAG | STAFLAG;

	/* Set it all going */
	IREG(I2CONSET) = STAFLAG;

	return TRUE;
}

void __attribute__((interrupt("IRQ"))) i2c_interrupt_handler(void)
{
	int stat = IREG(I2STAT);

	if (!i2c_transaction) {
		IREG(I2CONSET) = STOFLAG;
		IREG(I2CONCLR) = STAFLAG | AAFLAG | SIFLAG;
		interrupt_clear();
		return;
	}

	switch (stat) {

	case 0x08: /* START transmitted */
	case 0x10: /* repeated START transmitted */
		IREG(I2DAT) = i2c_transaction->address;
		IREG(I2CONCLR) = STAFLAG | STOFLAG | SIFLAG;
		i2c_bytes = 0;
		break;
	case 0x18: /* SA+W transmitted, ACK received */
	case 0x28: /* data transmitted, ACK received */
		if (i2c_bytes < i2c_transaction->bytes) {
			IREG(I2DAT) = i2c_transaction->data[i2c_bytes++];
			IREG(I2CONCLR) = STAFLAG | STOFLAG | SIFLAG;
		} else {
			*(i2c_transaction->result) = I2C_SUCCESS;
			if (i2c_transaction->next) {
				i2c_transaction = i2c_transaction->next;
				i2c_bytes = 0;
				IREG(I2CONSET) = STAFLAG;
				IREG(I2CONCLR) = STOFLAG | AAFLAG | SIFLAG;
			} else {
				i2c_transaction = NULL;
				IREG(I2CONSET) = STOFLAG;
				IREG(I2CONCLR) = STAFLAG | AAFLAG | SIFLAG;
			}
		}
		break;

	case 0x50: /* data received, ACK returned */
		i2c_transaction->data[i2c_bytes++] = IREG(I2DAT);
		/* fall through */

	case 0x40: /* SA+R transmitted, ACK received */
		if (i2c_bytes < (i2c_transaction->bytes-1)) {
			IREG(I2CONSET) = AAFLAG;
			IREG(I2CONCLR) = STAFLAG | STOFLAG | SIFLAG;
		} else {
			IREG(I2CONCLR) = STAFLAG | STOFLAG | SIFLAG 
							   | AAFLAG;
		}
		break;

	case 0x58: /* data received, NACK returned */
		i2c_transaction->data[i2c_bytes] = IREG(I2DAT);
		*(i2c_transaction->result) = I2C_SUCCESS;
		if (i2c_transaction->next) {
			i2c_transaction = i2c_transaction->next;
			i2c_bytes = 0;
			IREG(I2CONSET) = STAFLAG;
			IREG(I2CONCLR) = STOFLAG | AAFLAG | SIFLAG;
		} else {
			i2c_transaction = NULL;
			IREG(I2CONSET) = STOFLAG;
			IREG(I2CONCLR) = STAFLAG | AAFLAG | SIFLAG;
		}
		break;

	case 0x20: /* SA+W transmitted, NACK received */
	case 0x30: /* data transmitted, NACK received */
	case 0x48: /* SA+R transmitted, NACK received */
	case 0x38: /* arbitration lost during SA+W or data */
	case 0x00: /* bus error */
		*(i2c_transaction->result) = I2C_FAIL;
		i2c_transaction = NULL;
		IREG(I2CONSET) = STOFLAG;
		IREG(I2CONCLR) = STAFLAG | AAFLAG | SIFLAG;
		break;

	/* We don't handle slave mode */
	}

	interrupt_clear();
}