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/*
* TWIlib.c
*
* Created: 6/01/2014 10:41:33 PM
* Author: Chris Herring
*/
#include <avr/io.h>
#include <avr/interrupt.h>
#include "TWIlib.h"
#include <util/delay.h>
#include "print.h"
// Global transmit buffer
volatile uint8_t *TWITransmitBuffer;
// Global receive buffer
volatile uint8_t TWIReceiveBuffer[RXMAXBUFLEN];
// Buffer indexes
volatile int TXBuffIndex; // Index of the transmit buffer. Is volatile, can change at any time.
int RXBuffIndex; // Current index in the receive buffer
// Buffer lengths
int TXBuffLen; // The total length of the transmit buffer
int RXBuffLen; // The total number of bytes to read (should be less than RXMAXBUFFLEN)
TWIInfoStruct TWIInfo;
void TWIInit(void)
{
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(void)
{
if ( (TWIInfo.mode == Ready) | (TWIInfo.mode == RepeatedStartSent) )
{
// xprintf("i2c ready\n");
return 1;
}
else
{
if(TWIInfo.mode == Initializing){
switch(TWIInfo.errorCode){
case TWI_SUCCESS:
break;
case TWI_NO_RELEVANT_INFO:
break;
case TWI_LOST_ARBIT:
case TWI_MT_DATA_NACK:
// Some kind of I2C error, reset and re-init
xprintf("I2C init error: %d\n", TWIInfo.errorCode);
TWCR = (1 << TWINT)|(1 << TWSTO);
TWIInit();
break;
default:
xprintf("Other i2c init error: %d\n", TWIInfo.errorCode);
}
}
return 0;
}
}
void TWITransmitData(void *const TXdata, uint8_t dataLen, uint8_t repStart, uint8_t blocking)
{
// Wait until ready
while (!isTWIReady()) {_delay_us(1);}
// Reset the I2C stuff
TWCR = (1 << TWINT)|(1 << TWSTO);
TWIInit();
// Set repeated start mode
TWIInfo.repStart = repStart;
// Copy transmit info to global variables
TWITransmitBuffer = (uint8_t *)TXdata;
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();
}
if(blocking){
// Wait until ready
while (!isTWIReady()){_delay_us(1);}
}
}
// 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, 0);
}
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;
}
}
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