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/* I2C EEPROM memory read and write utilities
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA
*/
#include "board.h"
#include <stdbool.h>
/* Low-Level I2C Routines */
static const Pin pin_sda = {PIO_PA30, PIOA, ID_PIOA, PIO_OUTPUT_1, PIO_OPENDRAIN };
static const Pin pin_sda_in = {PIO_PA30, PIOA, ID_PIOA, PIO_INPUT, PIO_DEFAULT };
static const Pin pin_scl = {PIO_PA31, PIOA, ID_PIOA, PIO_OUTPUT_1, PIO_OPENDRAIN };
static void i2c_delay()
{
volatile int v;
int i;
/* 100 cycles results in SCL peak length of 44us, so it's about
* 440ns per cycle here */
for (i = 0; i < 14; i++) {
v = 0;
}
}
void i2c_pin_init(void)
{
PIO_Configure(&pin_scl, PIO_LISTSIZE(pin_scl));
PIO_Configure(&pin_sda, PIO_LISTSIZE(pin_sda));
}
static void set_scl(void)
{
PIO_Set(&pin_scl);
i2c_delay();
}
static void set_sda(void)
{
PIO_Set(&pin_sda);
i2c_delay();
}
static void clear_scl(void)
{
PIO_Clear(&pin_scl);
i2c_delay();
}
static void clear_sda(void)
{
PIO_Clear(&pin_sda);
i2c_delay();
}
static bool read_sda(void)
{
bool ret;
PIO_Configure(&pin_sda_in, PIO_LISTSIZE(pin_sda_in));
if (PIO_Get(&pin_sda_in))
ret = true;
else
ret = false;
PIO_Configure(&pin_sda, PIO_LISTSIZE(pin_sda));
return ret;
}
/* Core I2C Routines */
static bool i2c_started = false;
static void i2c_start_cond(void)
{
if (i2c_started) {
set_sda();
set_scl();
}
clear_sda();
i2c_delay();
clear_scl();
i2c_started = true;
}
static void i2c_stop_cond(void)
{
clear_sda();
set_scl();
set_sda();
i2c_delay();
i2c_started = false;
}
static void i2c_write_bit(bool bit)
{
if (bit)
set_sda();
else
clear_sda();
i2c_delay(); // ?
set_scl();
clear_scl();
}
static bool i2c_read_bit(void)
{
bool bit;
set_sda();
set_scl();
bit = read_sda();
clear_scl();
return bit;
}
bool i2c_write_byte(bool send_start, bool send_stop, uint8_t byte)
{
uint8_t bit;
bool nack;
if (send_start)
i2c_start_cond();
for (bit = 0; bit < 8; bit++) {
i2c_write_bit((byte & 0x80) != 0);
byte <<= 1;
}
nack = i2c_read_bit();
if (send_stop)
i2c_stop_cond();
return nack;
}
uint8_t i2c_read_byte(bool nack, bool send_stop)
{
uint8_t byte = 0;
uint8_t bit;
for (bit = 0; bit < 8; bit++) {
byte = (byte << 1) | i2c_read_bit();
}
i2c_write_bit(nack);
if (send_stop)
i2c_stop_cond();
return byte;
}
/* EEPROM related code */
int eeprom_write_byte(uint8_t slave, uint8_t addr, uint8_t byte)
{
bool nack;
WDT_Restart(WDT);
/* Write slave address */
nack = i2c_write_byte(true, false, slave << 1);
if (nack)
goto out_stop;
nack = i2c_write_byte(false, false, addr);
if (nack)
goto out_stop;
nack = i2c_write_byte(false, true, byte);
if (nack)
goto out_stop;
/* Wait tWR time to ensure EEPROM is writing correctly (tWR = 5 ms for AT24C02) */
mdelay(5);
out_stop:
i2c_stop_cond();
if (nack)
return -1;
else
return 0;
}
int eeprom_read_byte(uint8_t slave, uint8_t addr)
{
bool nack;
WDT_Restart(WDT);
/* dummy write cycle */
nack = i2c_write_byte(true, false, slave << 1);
if (nack)
goto out_stop;
nack = i2c_write_byte(false, false, addr);
if (nack)
goto out_stop;
/* Re-start with read */
nack = i2c_write_byte(true, false, (slave << 1) | 1);
if (nack)
goto out_stop;
return i2c_read_byte(true, true);
out_stop:
i2c_stop_cond();
if (nack)
return -1;
else
return 0;
}
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