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/****************************************************************************
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Title : C file for the I2C FUNCTIONS library (i2c.c)
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Author: Chris efstathiou hendrix@otenet.gr
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Date: 13/Jul/2002
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Software: AVR-GCC with AVR-AS
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Target: any AVR device
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Comments: This software is FREE.
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*****************************************************************************/
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#include <io.h>
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#include "i2c.h"
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#ifndef CONCAT1
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#define CONCAT1(a, b) CONCAT2(a, b)
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#endif
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#ifndef CONCAT2
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#define CONCAT2(a, b) a ## b
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#endif
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/* Conversion of microseconds to the right value for the delay function */
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#define I2C_DELAY ( (I2C_DELAY_TIME*(F_CPU/60000))/100 )
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#define I2C_TIMEOUT ( (I2C_TIMEOUT_TIME*(F_CPU/60000))/100 )
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/* Register name forming */
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#define I2C_SDA_OUT_REG CONCAT1(PORT, I2C_SDA_PORT)
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#define I2C_SCL_OUT_REG CONCAT1(PORT, I2C_SCL_PORT)
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#define I2C_SDA_DDR_REG CONCAT1(DDR, I2C_SDA_PORT)
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#define I2C_SCL_DDR_REG CONCAT1(DDR, I2C_SCL_PORT)
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#define I2C_SDA_PIN_REG CONCAT1(PIN, I2C_SDA_PORT)
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#define I2C_SCL_PIN_REG CONCAT1(PIN, I2C_SCL_PORT)
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/* Conversion of microseconds to the right value for the delay function */
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#define I2C_DELAY ( (I2C_DELAY_TIME*(F_CPU/60000))/100 )
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#define I2C_TIMEOUT ( (I2C_TIMEOUT_TIME*(F_CPU/60000))/100 )
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/* Pin states */
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#define SCL_1() cbi(I2C_SCL_DDR_REG, SCL_PIN)
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#define SCL_0() sbi(I2C_SCL_DDR_REG, SCL_PIN)
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#define SDA_1() cbi(I2C_SDA_DDR_REG, SDA_PIN)
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#define SDA_0() sbi(I2C_SDA_DDR_REG, SDA_PIN)
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#define RELEASE_I2C_BUS() { SCL_1(); SDA_1(); }
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/*#################################################################################################*/
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static void delay(unsigned long us)
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{
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while ( us ) { us--; } /* 6 cpu cycles per loop */
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}
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/*#################################################################################################*/
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void i2c_init(void)
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{
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cbi(I2C_SDA_OUT_REG, SDA_PIN);
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cbi(I2C_SCL_OUT_REG, SCL_PIN);
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RELEASE_I2C_BUS();
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delay(I2C_TIMEOUT);
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i2c_start();
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delay(I2C_TIMEOUT);
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i2c_stop();
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delay(I2C_TIMEOUT);
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return;
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}
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/*#################################################################################################*/
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void i2c_start(void)
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{
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RELEASE_I2C_BUS();
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delay(I2C_DELAY);
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SDA_0();
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delay(I2C_DELAY);
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SCL_0();
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delay(I2C_DELAY);
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return;
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}
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/*#################################################################################################*/
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void i2c_stop(void)
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{
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SDA_0();
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SCL_1();
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delay(I2C_DELAY);
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SDA_1();
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delay(I2C_DELAY);
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SCL_0();
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delay(I2C_DELAY);
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return;
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}
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/*#################################################################################################*/
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unsigned char i2c_transmit(unsigned char data)
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{
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register unsigned char bit=0;
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for(bit=0; bit<=7; bit++)
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{
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if( data & 0x80 ) { SDA_1(); } else { SDA_0(); }
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SCL_1();
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delay(I2C_DELAY);
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SCL_0();
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delay(I2C_DELAY);
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data = (data<<1);
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}
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/* Look for AKNOWLEDGE */
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RELEASE_I2C_BUS();
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delay(I2C_DELAY);
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if( bit_is_clear(I2C_SDA_PIN_REG, SDA_PIN) )
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{
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SCL_0();
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delay(I2C_DELAY);
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}
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else{
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delay(I2C_TIMEOUT);
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if( bit_is_clear(I2C_SDA_PIN_REG, SDA_PIN) )
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{
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SCL_0();
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delay(I2C_DELAY);
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}
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else { return(I2C_ERROR_DEVICE_NOT_RESPONDING); }
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}
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if( bit_is_clear(I2C_SDA_PIN_REG, SDA_PIN) )
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{
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delay(I2C_TIMEOUT);
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if( bit_is_clear(I2C_SDA_PIN_REG, SDA_PIN) ) { return(I2C_ERROR_DEVICE_BUSY); }
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}
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return(I2C_NO_ERROR);
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}
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/*#################################################################################################*/
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unsigned char i2c_receive(unsigned char ack)
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{
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register unsigned char bit=0, data=0;
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SDA_1();
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for(bit=0; bit<=7; bit++)
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{
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SCL_1();
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delay(I2C_DELAY);
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data = (data<<1);
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if( bit_is_set(I2C_SDA_PIN_REG, SDA_PIN) ) { data++; }
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SCL_0();
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delay(I2C_DELAY);
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}
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/* if CONTINUE then send AKNOWLEDGE else if QUIT do not send AKNOWLEDGE (send Nack) */
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if(ack==I2C_CONTINUE) { SDA_0(); } else { SDA_1(); }
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SCL_1();
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delay(I2C_DELAY);
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SCL_0();
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delay(I2C_DELAY);
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return data;
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}
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/*#################################################################################################*/
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