ledmodule.c

WWVB receiver using AVR.

/* $Id: ledmodule.c,v 1.17 2005/10/30 19:44:38 simimeie Exp $
 * Functions for communicating with the LED module.
 * The module is connected through an i2c bus, it consists of two SAA 1064
 * drivers.
 */ 
 
#define BV _BV
#include <avr/io.h>
#include <avr/delay.h>
#include "ledmodule.h"
#include "debugconsole.h"

/* The Port used for the connection */
#define LEDPORT PORTB
#define LEDPIN PINB
#define LEDDDR DDRB

/* Which pins of the port */
#define SDAPIN PB0
#define SCLPIN PB1

/* the I2C addresses of the SAA 1064 LED drivers */
#define SAA_AD1 0x70
#define SAA_AD2 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 14

/* For reference:
 * The mapping of the LED panel is as follows:
 *   Bit  Pin  Segment
 *    3    1    e       *  Segments:
 *    2    2    d       *    aaaa
 *    1    4    c       *   f    b
 *    0    5    P       *   f    b
 *    4    6    b       *    gggg
 *    5    7    a       *   e    c
 *    6    9    f       *   e    c
 *    7   10    g       *    dddd  P
 */
/* This is basically a "font" for the digits */
uint8_t led_digits[16] = { 0x7E, /* 0 */
			   0x12, /* 1 */
			   0xBC, /* 2 */
			   0xB6, /* 3 */
			   0xD2, /* 4 */
			   0xE6, /* 5 */
			   0xEE, /* 6 */
			   0x32, /* 7 */
			   0xFE, /* 8 */
			   0xF6, /* 9 */
			   0xFA, /* A */
			   0xCE, /* B */
			   0x6C, /* C */
			   0x9E, /* D */
			   0xEC, /* E */
			   0xE8  /* F */
			 };
uint8_t led_brightness;
uint8_t led_statusleds;
uint8_t led_dispoverride[7];
uint8_t led_dispovcnt;

void led_init(void) {
	/* activate pullups */
	LEDPORT |= BV(SCLPIN);
	LEDPORT |= BV(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 |= BV(SDAPIN);
	LEDDDR |= BV(SCLPIN);
	/* change SDA to low */
	LEDPORT &= (uint8_t)~BV(SDAPIN);
	_delay_loop_1(DELAYVAL);
	/* and SCL too */
	LEDPORT &= (uint8_t)~BV(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 |= BV(SCLPIN);
	_delay_loop_1(DELAYVAL);
	/* Set SDA */
	LEDPORT |= BV(SDAPIN);
	_delay_loop_1(DELAYVAL);
	/* Probably safer to tristate the bus */
	LEDDDR &= (uint8_t)~BV(SDAPIN);
	LEDDDR &= (uint8_t)~BV(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 |= BV(SDAPIN);
		}
		_delay_loop_1(DELAYVAL);
		/* Then set SCL high */
		LEDPORT |= BV(SCLPIN);
		_delay_loop_1(DELAYVAL);
		/* Take SCL back */
		LEDPORT &= (uint8_t)~BV(SCLPIN);
		_delay_loop_1(DELAYVAL);
		/* And SDA too */
		LEDPORT &= (uint8_t)~BV(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 |= BV(SDAPIN);
	LEDDDR &= (uint8_t)~BV(SDAPIN);
	/* Give the device some time */
	_delay_loop_1(DELAYVAL);
	_delay_loop_1(DELAYVAL);
	_delay_loop_1(DELAYVAL);
	/* Then set SCL high */
	LEDPORT |= BV(SCLPIN);
	_delay_loop_1(DELAYVAL);
	_delay_loop_1(DELAYVAL);
	_delay_loop_1(DELAYVAL);
	i = LEDPIN & BV(SDAPIN); /* Read ACK */
#if 0
	if (i) {
		debugconsole_print("!");
	} else {
		debugconsole_print("A");
	}
#endif
	/* Take SCL back */
	LEDPORT &= (uint8_t)~BV(SCLPIN);
	_delay_loop_1(DELAYVAL);
	/* No more tristate, we pull SDA again */
	LEDPORT &= (uint8_t)~BV(SDAPIN);
	LEDDDR |= BV(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((digit < 4) ? (SAA_AD1 | I2C_WRITE) : (SAA_AD2 | 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(void) {
	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();
	I2C_start();
	I2C_transmit_byte(SAA_AD2 | I2C_WRITE); /* Address second driver */
	I2C_transmit_byte(0); /* Address Config Register on device */
	I2C_transmit_byte(((led_brightness & 0x07) << 4) | 0x07); /* Send Settings */
	I2C_stop();
}