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42 pfowler 1 
#include <avr/io.h>
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#include "wire.h"
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#include "twi.h"
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#define		MAX_BUFFER	4
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void i2c_master(void) {
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	wire.rxBufferIndex = 0;
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	wire.rxBufferLength = 0;
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	wire.rxBufferIndex = 0;
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	wire.txBufferLength = 0;
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	twi_init();
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}
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void i2c_slave(uint8_t address) {
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	twi_setAddress(address);
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	//twi_attachSlaveTxEvent(&onRequestService);
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	//twi_attachSlaveRxEvent(&onReceiveService);
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	i2c_master();
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}
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uint8_t i2c_requestFrom(uint8_t address, uint8_t quantity, uint8_t sendStop) {
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	if (quantity > MAX_BUFFER) {
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		quantity = MAX_BUFFER;
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	}
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	uint8_t read = twi_readFrom(address, wire.rxBuffer, quantity, sendStop);
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	wire.rxBufferIndex = 0;
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	wire.rxBufferLength = read;
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	return read;
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}
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void i2c_beginTransmission(uint8_t address) {
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	wire.transmitting = 1;
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	wire.txAddress = address;
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	wire.txBufferIndex = 0;
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	wire.txBufferLength = 0;
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}
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uint8_t i2c_endTransmission(uint8_t sendStop) {
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	int8_t ret = twi_writeTo(wire.txAddress,
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					wire.txBuffer,
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					wire.txBufferLength,
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					1, sendStop);
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	wire.txBufferIndex = 0;
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	wire.txBufferLength = 0;
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	wire.transmitting = 0;
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	return ret;
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}
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uint8_t i2c_writeByte(uint8_t data) {
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	if (wire.transmitting) {
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		if (wire.txBufferLength >= MAX_BUFFER) {
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			//setWriteError();
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			return 0;
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		}
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		wire.txBuffer[wire.txBufferIndex] = data;
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		++wire.txBufferIndex;
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		wire.txBufferLength = wire.txBufferIndex;
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	} else {
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		twi_transmit(&data, 1);
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	}
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	return 1;
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}
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uint8_t i2c_writeBytes(uint8_t *data, uint8_t bytes) {
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	if (wire.transmitting) {
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		uint8_t i = 0;
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		for (i = 0; i < bytes; i++) {
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			i2c_writeByte(data[i]);
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		}
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	} else {
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		twi_transmit(data, bytes);
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	}
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	return bytes;
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}
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int i2c_available(void) {
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	return wire.rxBufferLength - wire.rxBufferIndex;
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}
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uint8_t i2c_read(void) {
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	int value = 0;
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	if (wire.rxBufferIndex < wire.rxBufferLength) {
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		value = wire.rxBuffer[wire.rxBufferIndex];
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		++wire.rxBufferIndex;
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	}
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	return value;
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}
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void i2c_onReceiveService(uint8_t* inBytes, int numBytes) {
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	if(!wire.user_onReceive) {
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		return;
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	}
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	if(wire.rxBufferIndex < wire.rxBufferLength) {
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		return;
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	}
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	uint8_t i = 0;
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	for(i = 0; i < numBytes; ++i) {
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		wire.rxBuffer[i] = inBytes[i];
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	}
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	wire.rxBufferIndex = 0;
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	wire.rxBufferLength = numBytes;
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	wire.user_onReceive(numBytes);
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}
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void i2c_onRequestService(void) {
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	if(!wire.user_onRequest) {
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		return;
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	}
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	wire.txBufferIndex = 0;
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	wire.txBufferLength = 0;
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	wire.user_onRequest();
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}
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void i2c_onReceive( void(*function)(uint8_t)) {
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	wire.user_onReceive = function;
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}
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void i2c_onRequest( void(*function)(void)) {
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	wire.user_onRequest = function;
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}