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