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138 pfowler 1 
/*
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 * i2cbb.c
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 *
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 *	Bit Banging I2C code for any Atmel device
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 *		The I2CBB_DELAY delay (in header) may need to be tweaked
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 *		for different clock speeds, 10 if a fast enough
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 *		speed, 100 if your having problems and dont need
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 *		the speed. 7 seems to work well with an Attiny85
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 *		running the PLL 16.5Mhz clock.
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 *
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 *		Base code from Raul
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 *		http://codinglab.blogspot.com.au/2008/10/i2c-on-avr-using-bit-banging.html
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 */
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#include <avr/io.h>
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#include <util/delay.h>
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#include "config.h"
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#include "avrutil.h"
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#include "i2cbb.h"
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#define I2CBB_DATA_HI()\
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I2CBB_DDR &= ~ (1 << I2CBB_DAT);\
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I2CBB_PORT |= (1 << I2CBB_DAT);
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#define I2CBB_DATA_LO()\
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I2CBB_DDR |= (1 << I2CBB_DAT);\
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I2CBB_PORT &= ~ (1 << I2CBB_DAT);
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#define I2CBB_CLOCK_HI()\
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I2CBB_DDR &= ~ (1 << I2CBB_CLK);\
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I2CBB_PORT |= (1 << I2CBB_CLK);
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#define I2CBB_CLOCK_LO()\
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I2CBB_DDR |= (1 << I2CBB_CLK);\
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I2CBB_PORT &= ~ (1 << I2CBB_CLK);
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void i2cbb_WriteBit(unsigned char c) {
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    if (c > 0) {
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        I2CBB_DATA_HI();
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    }
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    else {
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        I2CBB_DATA_LO();
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    }
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    I2CBB_CLOCK_HI();
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    while ((I2CBB_PIN & (1 << I2CBB_CLK)) == 0);
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    _delay_us(I2CBB_DELAY);
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    I2CBB_CLOCK_LO();
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    //_delay_us(I2CBB_DELAY);
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    if (c > 0) {
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    	_delay_us(I2CBB_DELAY); // Added
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        I2CBB_DATA_LO();
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    }
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//    _delay_us(I2CBB_DELAY);
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}
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unsigned char i2cbb_ReadBit() {
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    I2CBB_DATA_HI();
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    I2CBB_CLOCK_HI();
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    while ((I2CBB_PIN & (1 << I2CBB_CLK)) == 0);
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    _delay_us(I2CBB_DELAY);
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    unsigned char c = I2CBB_PIN;
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    I2CBB_CLOCK_LO();
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    //_delay_us(I2CBB_DELAY);
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    return (c >> I2CBB_DAT) & 1;
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}
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// Inits bitbanging port, must be called before using the functions below
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//
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void i2cbb_Init() {
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    I2CBB_PORT &= ~ ((1 << I2CBB_DAT) | (1 << I2CBB_CLK));
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    I2CBB_CLOCK_HI();
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    I2CBB_DATA_HI();
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    _delay_us(I2CBB_DELAY);
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}
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// Send a START Condition
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//
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void i2cbb_Start() {
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    // set both to high at the same time
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    I2CBB_DDR &= ~ ((1 << I2CBB_DAT) | (1 << I2CBB_CLK));
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    _delay_us(I2CBB_DELAY);
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    I2CBB_DATA_LO();
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    _delay_us(I2CBB_DELAY);
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    I2CBB_CLOCK_LO();
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    _delay_us(I2CBB_DELAY);
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}
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// Send a STOP Condition
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//
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void i2cbb_Stop() {
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    I2CBB_DATA_LO();
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    I2CBB_CLOCK_LO();
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    _delay_us(I2CBB_DELAY);
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    _delay_us(I2CBB_DELAY);
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    I2CBB_CLOCK_HI();
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    _delay_us(I2CBB_DELAY);
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    _delay_us(I2CBB_DELAY);
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    I2CBB_DATA_HI();
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    //_delay_us(I2CBB_DELAY);
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}
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// write a byte to the I2C slave device
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unsigned char i2cbb_Write(unsigned char c) {
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	uint8_t i;
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    for (i=0; i < 8; i++) {
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    	i2cbb_WriteBit(c & 128);
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        c <<= 1;
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    }
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    return i2cbb_ReadBit();
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    //return 0;
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}
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// read a byte from the I2C slave device
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//
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unsigned char i2cbb_Read(unsigned char ack) {
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    unsigned char res = 0;
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    uint8_t i;
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    for (i = 0; i < 8; i++) {
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        res <<= 1;
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        res |= i2cbb_ReadBit();
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    }
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    if (ack > 0) {
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    	i2cbb_WriteBit(0);
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    }
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    else {
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    	i2cbb_WriteBit(1);
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    }
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    //_delay_us(I2CBB_DELAY);
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    return res;
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}