/**
 * \file saa1064.c
 * \brief I2C-connection to the SAA1064 LED-driver
 * \author Ronald Schaten
 * \version $Id: saa1064.c,v 1.1 2007/01/02 21:30:40 rschaten Exp $
 *
 * License: See documentation.
 */

/* based on http://www.mulder.franken.de/ntpdcfledclock/ */

#include <avr/io.h>
#include <util/delay.h>
#include "saa1064.h"

/* The Port used for the connection */
#define LEDPORT PORTC
#define LEDPIN PINC
#define LEDDDR DDRC

/* Which pins of the port */
#define SDAPIN PC4
#define SCLPIN PC5

/* the I2C addresses of the SAA 1064 LED drivers */
#define SAA_AD1 0x70 // or 0x76?

#define I2C_READ  0x01
#define I2C_WRITE 0x00

/* Should be at least 27 (80 / 3) at 8 MHz */
/* This was the conservative value used for testing. However, half as much should work as well. */
#define DELAYVAL 3

void led_init(void) {
    /* activate pullups */
    LEDPORT |= (1 << SCLPIN) | (1 << SDAPIN);
}

/* Send START, defined as high-to-low SDA with SCL high.
 * Expects SCL and SDA to be high already!
 * Returns with SDA and SCL low. */
static void I2C_start(void) {
    /* Change to output mode. */
    LEDDDR |= (1 << SDAPIN) | (1 << SCLPIN);
    /* change SDA to low */
    LEDPORT &= ~(1 << SDAPIN);
    _delay_loop_1(DELAYVAL);
    /* and SCL too */
    LEDPORT &= ~(1 << SCLPIN);
    _delay_loop_1(DELAYVAL);
}

/* Send STOP, defined as low-to-high SDA with SCL high.
 * Expects SCL and SDA to be low already!
 * Returns with SDA and SCL high. */
static void I2C_stop(void) {
    /* Set SCL */
    LEDPORT |= (1 << SCLPIN);
    _delay_loop_1(DELAYVAL);
    /* Set SDA */
    LEDPORT |= (1 << SDAPIN);
    _delay_loop_1(DELAYVAL);
    /* Probably safer to tristate the bus */
    LEDDDR &= ~((1 << SDAPIN) | (1 << SCLPIN));
}

/* Transmits the byte in what.
 * Returns 1 if the byte was ACKed, 0 if not.
 * Expects SCL and SDA to be low already!
 * Returns with SDA and SCL low. */
static uint8_t I2C_transmit_byte(uint8_t what) {
    uint8_t i;
    for (i = 0; i < 8; i++) {
        /* First put data on the bus */
        if (what & 0x80) {
            LEDPORT |= (1 << SDAPIN);
        }
        _delay_loop_1(DELAYVAL);
        /* Then set SCL high */
        LEDPORT |= (1 << SCLPIN);
        _delay_loop_1(DELAYVAL);
        /* Take SCL back */
        LEDPORT &= ~(1 << SCLPIN);
        _delay_loop_1(DELAYVAL);
        /* And SDA too */
        LEDPORT &= ~(1 << SDAPIN);
        _delay_loop_1(DELAYVAL);
        what <<= 1;
    }
    /* OK that was the data, now we read back the ACK */
    /* We need to tristate SDA for that */
    LEDPORT |= (1 << SDAPIN);
    LEDDDR &= ~(1 << SDAPIN);
    /* Give the device some time */
    _delay_loop_1(DELAYVAL);
    _delay_loop_1(DELAYVAL);
    _delay_loop_1(DELAYVAL);
    /* Then set SCL high */
    LEDPORT |= (1 << SCLPIN);
    _delay_loop_1(DELAYVAL);
    _delay_loop_1(DELAYVAL);
    _delay_loop_1(DELAYVAL);
    i = LEDPIN & (1 << SDAPIN);    /* Read ACK */
    /* Take SCL back */
    LEDPORT &= ~(1 << SCLPIN);
    _delay_loop_1(DELAYVAL);
    /* No more tristate, we pull SDA again */
    LEDPORT &= ~(1 << SDAPIN);
    LEDDDR |= (1 << SDAPIN);
    _delay_loop_1(DELAYVAL);
    return (i == 0);
}

void set_led_digit(uint8_t digit, uint8_t val) {
    I2C_start();
    /* Address device */
    I2C_transmit_byte(SAA_AD1 | I2C_WRITE);
    I2C_transmit_byte((digit & 3) + 1); /* Address Digit Register on device */
    I2C_transmit_byte(val);     /* Send value for Digit */
    I2C_stop();
}

void set_led_brightness(uint8_t led_brightness) {
    I2C_start();
    I2C_transmit_byte(SAA_AD1 | I2C_WRITE);     /* Address first driver */
    I2C_transmit_byte(0);       /* Address Config Register on device */
    I2C_transmit_byte(((led_brightness & 0x07) << 4) | 0x07);   /* Send Settings */
    I2C_stop();
}