233 lines
6.2 KiB
C
233 lines
6.2 KiB
C
/*
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* TWIlib.c
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*
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* Created: 6/01/2014 10:41:33 PM
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* Author: Chris Herring
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* http://www.chrisherring.net/all/tutorial-interrupt-driven-twi-interface-for-avr-part1/
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*/
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#include <avr/io.h>
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#include <avr/interrupt.h>
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#include "TWIlib.h"
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#include "util/delay.h"
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void TWIInit()
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{
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TWIInfo.mode = Ready;
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TWIInfo.errorCode = 0xFF;
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TWIInfo.repStart = 0;
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// Set pre-scalers (no pre-scaling)
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TWSR = 0;
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// Set bit rate
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TWBR = ((F_CPU / TWI_FREQ) - 16) / 2;
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// Enable TWI and interrupt
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TWCR = (1 << TWIE) | (1 << TWEN);
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}
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uint8_t isTWIReady()
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{
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if ( (TWIInfo.mode == Ready) | (TWIInfo.mode == RepeatedStartSent) )
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{
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return 1;
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}
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else
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{
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return 0;
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}
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}
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uint8_t TWITransmitData(void *const TXdata, uint8_t dataLen, uint8_t repStart)
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{
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if (dataLen <= TXMAXBUFLEN)
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{
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// Wait until ready
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while (!isTWIReady()) {_delay_us(1);}
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// Set repeated start mode
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TWIInfo.repStart = repStart;
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// Copy data into the transmit buffer
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uint8_t *data = (uint8_t *)TXdata;
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for (int i = 0; i < dataLen; i++)
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{
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TWITransmitBuffer[i] = data[i];
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}
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// Copy transmit info to global variables
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TXBuffLen = dataLen;
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TXBuffIndex = 0;
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// If a repeated start has been sent, then devices are already listening for an address
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// and another start does not need to be sent.
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if (TWIInfo.mode == RepeatedStartSent)
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{
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TWIInfo.mode = Initializing;
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TWDR = TWITransmitBuffer[TXBuffIndex++]; // Load data to transmit buffer
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TWISendTransmit(); // Send the data
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}
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else // Otherwise, just send the normal start signal to begin transmission.
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{
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TWIInfo.mode = Initializing;
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TWISendStart();
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}
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}
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else
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{
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return 1; // return an error if data length is longer than buffer
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}
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return 0;
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}
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uint8_t TWIReadData(uint8_t TWIaddr, uint8_t bytesToRead, uint8_t repStart)
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{
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// Check if number of bytes to read can fit in the RXbuffer
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if (bytesToRead < RXMAXBUFLEN)
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{
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// Reset buffer index and set RXBuffLen to the number of bytes to read
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RXBuffIndex = 0;
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RXBuffLen = bytesToRead;
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// Create the one value array for the address to be transmitted
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uint8_t TXdata[1];
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// Shift the address and AND a 1 into the read write bit (set to write mode)
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TXdata[0] = (TWIaddr << 1) | 0x01;
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// Use the TWITransmitData function to initialize the transfer and address the slave
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TWITransmitData(TXdata, 1, repStart);
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}
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else
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{
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return 0;
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}
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return 1;
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}
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ISR (TWI_vect)
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{
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switch (TWI_STATUS)
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{
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// ----\/ ---- MASTER TRANSMITTER OR WRITING ADDRESS ----\/ ---- //
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case TWI_MT_SLAW_ACK: // SLA+W transmitted and ACK received
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// Set mode to Master Transmitter
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TWIInfo.mode = MasterTransmitter;
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case TWI_START_SENT: // Start condition has been transmitted
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case TWI_MT_DATA_ACK: // Data byte has been transmitted, ACK received
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if (TXBuffIndex < TXBuffLen) // If there is more data to send
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{
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TWDR = TWITransmitBuffer[TXBuffIndex++]; // Load data to transmit buffer
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TWIInfo.errorCode = TWI_NO_RELEVANT_INFO;
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TWISendTransmit(); // Send the data
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}
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// This transmission is complete however do not release bus yet
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else if (TWIInfo.repStart)
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{
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TWIInfo.errorCode = 0xFF;
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TWISendStart();
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}
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// All transmissions are complete, exit
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else
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{
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TWIInfo.mode = Ready;
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TWIInfo.errorCode = 0xFF;
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TWISendStop();
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}
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break;
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// ----\/ ---- MASTER RECEIVER ----\/ ---- //
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case TWI_MR_SLAR_ACK: // SLA+R has been transmitted, ACK has been received
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// Switch to Master Receiver mode
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TWIInfo.mode = MasterReceiver;
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// If there is more than one byte to be read, receive data byte and return an ACK
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if (RXBuffIndex < RXBuffLen-1)
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{
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TWIInfo.errorCode = TWI_NO_RELEVANT_INFO;
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TWISendACK();
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}
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// Otherwise when a data byte (the only data byte) is received, return NACK
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else
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{
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TWIInfo.errorCode = TWI_NO_RELEVANT_INFO;
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TWISendNACK();
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}
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break;
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case TWI_MR_DATA_ACK: // Data has been received, ACK has been transmitted.
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/// -- HANDLE DATA BYTE --- ///
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TWIReceiveBuffer[RXBuffIndex++] = TWDR;
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// If there is more than one byte to be read, receive data byte and return an ACK
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if (RXBuffIndex < RXBuffLen-1)
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{
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TWIInfo.errorCode = TWI_NO_RELEVANT_INFO;
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TWISendACK();
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}
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// Otherwise when a data byte (the only data byte) is received, return NACK
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else
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{
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TWIInfo.errorCode = TWI_NO_RELEVANT_INFO;
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TWISendNACK();
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}
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break;
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case TWI_MR_DATA_NACK: // Data byte has been received, NACK has been transmitted. End of transmission.
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/// -- HANDLE DATA BYTE --- ///
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TWIReceiveBuffer[RXBuffIndex++] = TWDR;
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// This transmission is complete however do not release bus yet
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if (TWIInfo.repStart)
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{
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TWIInfo.errorCode = 0xFF;
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TWISendStart();
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}
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// All transmissions are complete, exit
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else
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{
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TWIInfo.mode = Ready;
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TWIInfo.errorCode = 0xFF;
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TWISendStop();
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}
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break;
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// ----\/ ---- MT and MR common ----\/ ---- //
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case TWI_MR_SLAR_NACK: // SLA+R transmitted, NACK received
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case TWI_MT_SLAW_NACK: // SLA+W transmitted, NACK received
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case TWI_MT_DATA_NACK: // Data byte has been transmitted, NACK received
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case TWI_LOST_ARBIT: // Arbitration has been lost
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// Return error and send stop and set mode to ready
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if (TWIInfo.repStart)
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{
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TWIInfo.errorCode = TWI_STATUS;
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TWISendStart();
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}
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// All transmissions are complete, exit
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else
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{
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TWIInfo.mode = Ready;
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TWIInfo.errorCode = TWI_STATUS;
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TWISendStop();
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}
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break;
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case TWI_REP_START_SENT: // Repeated start has been transmitted
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// Set the mode but DO NOT clear TWINT as the next data is not yet ready
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TWIInfo.mode = RepeatedStartSent;
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break;
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// ----\/ ---- SLAVE RECEIVER ----\/ ---- //
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// TODO IMPLEMENT SLAVE RECEIVER FUNCTIONALITY
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// ----\/ ---- SLAVE TRANSMITTER ----\/ ---- //
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// TODO IMPLEMENT SLAVE TRANSMITTER FUNCTIONALITY
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// ----\/ ---- MISCELLANEOUS STATES ----\/ ---- //
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case TWI_NO_RELEVANT_INFO: // It is not really possible to get into this ISR on this condition
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// Rather, it is there to be manually set between operations
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break;
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case TWI_ILLEGAL_START_STOP: // Illegal START/STOP, abort and return error
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TWIInfo.errorCode = TWI_ILLEGAL_START_STOP;
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TWIInfo.mode = Ready;
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TWISendStop();
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break;
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}
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}
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