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13 pfowler 1 
/*
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 * twires.c
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 *
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 *  Created on: 16/07/2014
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 *      Author: pfowler
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 *
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 *       USAGE is modeled after the TinyWireS . . . which is modeled on standard Wire library . . .
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 *
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 * Put in setup():
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 *	TinyWireS.begin(I2C_SLAVE_ADDR);                 // initialize I2C lib & setup slave's address (7 bit - same as Wire)
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 *
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 * To Receive:
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 *   someByte = TinyWireS.available(){                // returns the number of bytes in the received buffer
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 *   someByte = TinyWireS.receive(){                  // returns the next byte in the received buffer
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 *
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 * To Send:
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 *	TinyWireS.send(uint8_t data){                    // sends a requested byte to master
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 *
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 * TODO:	(by others!)
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 *	- onReceive and onRequest handlers are not implemented.
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 *	- merge this class with TinyWireM for master & slave support in one library
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 */
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#include <inttypes.h>
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#include "usiTwiSlave.h"
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#include <avr/interrupt.h>
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#include "avrutil.h"
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#include "twires.h"
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void twires_begin(uint8_t slaveAddr) {
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	usiTwiSlaveInit(slaveAddr);
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}
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void twires_send(uint8_t data) {
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	usiTwiTransmitByte(data);
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}
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uint8_t twires_available() {
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	return usiTwiAmountDataInReceiveBuffer();
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}
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uint8_t twires_receive() {
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	return usiTwiReceiveByte();
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}
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void twires_onReceive( void (*function)(uint8_t) ) {
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	usi_onReceiverPtr = function;
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}
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void twires_onRequest( void (*function)(void) ) {
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	usi_onRequestPtr = function;
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}
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void twires_stop_check() {
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	if (!usi_onReceiverPtr) {
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		// No onreceive callback
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		return;
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	}
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	if (!(USISR & ( 1 << USIPF ))) {
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		//Stop not detected
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		return;
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	}
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	uint8_t amount = usiTwiAmountDataInReceiveBuffer();
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	if (amount==0) {
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		return;
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	}
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	usi_onReceiverPtr(amount);
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}
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/*
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 * Use this instead of the delay function. The twires_stop_check()
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 * needs to be called lots of times to detect the stop condition
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 */
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void twires_delay(unsigned long ms) {
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    uint16_t start = (uint16_t)millis();
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    while (ms > 0)
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    {
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    	twires_stop_check();
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        if (((uint16_t)millis() - start) >= 1)
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        {
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            ms--;
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            start += 1;
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        }
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    }
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}
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