131 lines
3.7 KiB
C
131 lines
3.7 KiB
C
/**
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* \file saa1064.c
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* \brief I2C-connection to the SAA1064 LED-driver
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* \author Ronald Schaten
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* \version $Id: saa1064.c,v 1.1 2007/01/02 21:30:40 rschaten Exp $
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*
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* License: See documentation.
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*/
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/* based on http://www.mulder.franken.de/ntpdcfledclock/ */
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#include <avr/io.h>
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#include <util/delay.h>
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#include "saa1064.h"
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/* The Port used for the connection */
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#define LEDPORT PORTC
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#define LEDPIN PINC
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#define LEDDDR DDRC
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/* Which pins of the port */
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#define SDAPIN PC4
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#define SCLPIN PC5
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/* the I2C addresses of the SAA 1064 LED drivers */
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#define SAA_AD1 0x70 // or 0x76?
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#define I2C_READ 0x01
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#define I2C_WRITE 0x00
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/* Should be at least 27 (80 / 3) at 8 MHz */
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/* This was the conservative value used for testing. However, half as much should work as well. */
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#define DELAYVAL 3
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void led_init(void) {
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/* activate pullups */
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LEDPORT |= (1 << SCLPIN) | (1 << SDAPIN);
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}
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/* Send START, defined as high-to-low SDA with SCL high.
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* Expects SCL and SDA to be high already!
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* Returns with SDA and SCL low. */
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static void I2C_start(void) {
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/* Change to output mode. */
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LEDDDR |= (1 << SDAPIN) | (1 << SCLPIN);
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/* change SDA to low */
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LEDPORT &= ~(1 << SDAPIN);
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_delay_loop_1(DELAYVAL);
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/* and SCL too */
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LEDPORT &= ~(1 << SCLPIN);
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_delay_loop_1(DELAYVAL);
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}
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/* Send STOP, defined as low-to-high SDA with SCL high.
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* Expects SCL and SDA to be low already!
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* Returns with SDA and SCL high. */
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static void I2C_stop(void) {
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/* Set SCL */
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LEDPORT |= (1 << SCLPIN);
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_delay_loop_1(DELAYVAL);
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/* Set SDA */
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LEDPORT |= (1 << SDAPIN);
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_delay_loop_1(DELAYVAL);
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/* Probably safer to tristate the bus */
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LEDDDR &= ~((1 << SDAPIN) | (1 << SCLPIN));
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}
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/* Transmits the byte in what.
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* Returns 1 if the byte was ACKed, 0 if not.
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* Expects SCL and SDA to be low already!
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* Returns with SDA and SCL low. */
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static uint8_t I2C_transmit_byte(uint8_t what) {
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uint8_t i;
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for (i = 0; i < 8; i++) {
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/* First put data on the bus */
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if (what & 0x80) {
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LEDPORT |= (1 << SDAPIN);
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}
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_delay_loop_1(DELAYVAL);
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/* Then set SCL high */
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LEDPORT |= (1 << SCLPIN);
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_delay_loop_1(DELAYVAL);
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/* Take SCL back */
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LEDPORT &= ~(1 << SCLPIN);
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_delay_loop_1(DELAYVAL);
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/* And SDA too */
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LEDPORT &= ~(1 << SDAPIN);
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_delay_loop_1(DELAYVAL);
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what <<= 1;
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}
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/* OK that was the data, now we read back the ACK */
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/* We need to tristate SDA for that */
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LEDPORT |= (1 << SDAPIN);
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LEDDDR &= ~(1 << SDAPIN);
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/* Give the device some time */
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_delay_loop_1(DELAYVAL);
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_delay_loop_1(DELAYVAL);
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_delay_loop_1(DELAYVAL);
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/* Then set SCL high */
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LEDPORT |= (1 << SCLPIN);
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_delay_loop_1(DELAYVAL);
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_delay_loop_1(DELAYVAL);
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_delay_loop_1(DELAYVAL);
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i = LEDPIN & (1 << SDAPIN); /* Read ACK */
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/* Take SCL back */
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LEDPORT &= ~(1 << SCLPIN);
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_delay_loop_1(DELAYVAL);
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/* No more tristate, we pull SDA again */
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LEDPORT &= ~(1 << SDAPIN);
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LEDDDR |= (1 << SDAPIN);
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_delay_loop_1(DELAYVAL);
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return (i == 0);
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}
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void set_led_digit(uint8_t digit, uint8_t val) {
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I2C_start();
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/* Address device */
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I2C_transmit_byte(SAA_AD1 | I2C_WRITE);
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I2C_transmit_byte((digit & 3) + 1); /* Address Digit Register on device */
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I2C_transmit_byte(val); /* Send value for Digit */
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I2C_stop();
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}
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void set_led_brightness(uint8_t led_brightness) {
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I2C_start();
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I2C_transmit_byte(SAA_AD1 | I2C_WRITE); /* Address first driver */
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I2C_transmit_byte(0); /* Address Config Register on device */
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I2C_transmit_byte(((led_brightness & 0x07) << 4) | 0x07); /* Send Settings */
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I2C_stop();
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}
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