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/*! \file i2c.c \brief I2C interface using AVR Two-Wire Interface (TWI) hardware. */
//*****************************************************************************
//
// File Name : 'i2c.c'
// Title : I2C interface using AVR Two-Wire Interface (TWI) hardware
// Author : Pascal Stang - Copyright (C) 2002-2003
// Created : 2002.06.25
// Revised : 2003.03.02
// Version : 0.9
// Target MCU : Atmel AVR series
// Editor Tabs : 4
//
// This code is distributed under the GNU Public License
// which can be found at http://www.gnu.org/licenses/gpl.txt
//
//*****************************************************************************
#include <avr/io.h>
#include <avr/interrupt.h>
#include "i2c.h"
#include "util.h"
// Standard I2C bit rates are:
// 100KHz for slow speed
// 400KHz for high speed
#define I2C_DEBUG 1
// I2C state and address variables
static volatile eI2cStateType I2cState;
static u08 I2cDeviceAddrRW;
// send/transmit buffer (outgoing data)
static u08 I2cSendData[I2C_SEND_DATA_BUFFER_SIZE];
static u08 I2cSendDataIndex;
static u08 I2cSendDataLength;
// receive buffer (incoming data)
static u08 I2cReceiveData[I2C_RECEIVE_DATA_BUFFER_SIZE];
static u08 I2cReceiveDataIndex;
static u08 I2cReceiveDataLength;
// function pointer to i2c receive routine
//! I2cSlaveReceive is called when this processor
// is addressed as a slave for writing
static void (*i2cSlaveReceive)(u08 receiveDataLength, u08* recieveData);
//! I2cSlaveTransmit is called when this processor
// is addressed as a slave for reading
static u08 (*i2cSlaveTransmit)(u08 transmitDataLengthMax, u08* transmitData);
// functions
void i2cInit(void)
{
// set pull-up resistors on I2C bus pins
// TODO: should #ifdef these
sbi(PORTC, 5); // i2c SCL on ATmegaxx8
sbi(PORTC, 4); // i2c SDA on ATmegaxx8
// clear SlaveReceive and SlaveTransmit handler to null
i2cSlaveReceive = 0;
i2cSlaveTransmit = 0;
// set i2c bit rate to 100KHz
i2cSetBitrate(100);
// enable TWI (two-wire interface)
sbi(TWCR, TWEN);
// set state
I2cState = I2C_IDLE;
// enable TWI interrupt and slave address ACK
sbi(TWCR, TWIE);
sbi(TWCR, TWEA);
//outb(TWCR, (inb(TWCR)&TWCR_CMD_MASK)|BV(TWINT)|BV(TWEA));
// enable interrupts
sei();
}
void i2cSetBitrate(u16 bitrate)
{
u08 bitrate_div;
// set i2c bitrate
// SCL freq = F_CPU/(16+2*TWBR))
/*
#ifdef TWPS0
// for processors with additional bitrate division (mega128)
// SCL freq = F_CPU/(16+2*TWBR*4^TWPS)
// set TWPS to zero
cbi(TWSR, TWPS0);
cbi(TWSR, TWPS1);
#endif
*/
// calculate bitrate division
bitrate_div = (F_CPU/32)/bitrate;
//outb(TWBR, bitrate_div);
TWBR = 32;
}
void i2cSetLocalDeviceAddr(u08 deviceAddr, u08 genCallEn)
{
// set local device address (used in slave mode only)
outb(TWAR, ((deviceAddr&0xFE) | (genCallEn?1:0)) );
}
void i2cSetSlaveReceiveHandler(void (*i2cSlaveRx_func)(u08 receiveDataLength, u08* recieveData))
{
i2cSlaveReceive = i2cSlaveRx_func;
}
void i2cSetSlaveTransmitHandler(u08 (*i2cSlaveTx_func)(u08 transmitDataLengthMax, u08* transmitData))
{
i2cSlaveTransmit = i2cSlaveTx_func;
}
inline void i2cSendStart(void)
{
// send start condition
outb(TWCR, (inb(TWCR)&TWCR_CMD_MASK)|BV(TWINT)|BV(TWSTA));
}
inline void i2cSendStop(void)
{
// transmit stop condition
// leave with TWEA on for slave receiving
outb(TWCR, (inb(TWCR)&TWCR_CMD_MASK)|BV(TWINT)|BV(TWEA)|BV(TWSTO));
}
inline void i2cWaitForComplete(void)
{
// wait for i2c interface to complete operation
while( !(inb(TWCR) & BV(TWINT)) );
}
inline void i2cSendByte(u08 data)
{
// save data to the TWDR
outb(TWDR, data);
// begin send
outb(TWCR, (inb(TWCR)&TWCR_CMD_MASK)|BV(TWINT));
}
inline void i2cReceiveByte(u08 ackFlag)
{
// begin receive over i2c
if( ackFlag )
{
// ackFlag = TRUE: ACK the recevied data
outb(TWCR, (inb(TWCR)&TWCR_CMD_MASK)|BV(TWINT)|BV(TWEA));
}
else
{
// ackFlag = FALSE: NACK the recevied data
outb(TWCR, (inb(TWCR)&TWCR_CMD_MASK)|BV(TWINT));
}
}
inline u08 i2cGetReceivedByte(void)
{
// retieve received data byte from i2c TWDR
return( inb(TWDR) );
}
inline u08 i2cGetStatus(void)
{
// retieve current i2c status from i2c TWSR
return( inb(TWSR) );
}
void i2cMasterSend(u08 deviceAddr, u08 length, u08* data)
{
u08 i;
// wait for interface to be ready
while(I2cState);
// set state
I2cState = I2C_MASTER_TX;
// save data
I2cDeviceAddrRW = (deviceAddr & 0xFE); // RW cleared: write operation
for(i=0; i<length; i++)
I2cSendData[i] = *data++;
I2cSendDataIndex = 0;
I2cSendDataLength = length;
// send start condition
i2cSendStart();
}
void i2cMasterReceive(u08 deviceAddr, u08 length, u08* data)
{
u08 i;
// wait for interface to be ready
while(I2cState);
// set state
I2cState = I2C_MASTER_RX;
// save data
I2cDeviceAddrRW = (deviceAddr|0x01); // RW set: read operation
I2cReceiveDataIndex = 0;
I2cReceiveDataLength = length;
// send start condition
i2cSendStart();
// wait for data
while(I2cState);
// return data
for(i=0; i<length; i++)
*data++ = I2cReceiveData[i];
}
u08 i2cMasterSendNI(u08 deviceAddr, u08 length, u08* data)
{
u08 retval = I2C_OK;
// disable TWI interrupt
cbi(TWCR, TWIE);
// send start condition
i2cSendStart();
i2cWaitForComplete();
// send device address with write
i2cSendByte( deviceAddr & 0xFE );
i2cWaitForComplete();
// check if device is present and live
if( inb(TWSR) == TW_MT_SLA_ACK)
{
// send data
while(length)
{
i2cSendByte( *data++ );
i2cWaitForComplete();
length--;
}
}
else
{
// device did not ACK it's address,
// data will not be transferred
// return error
retval = I2C_ERROR_NODEV;
}
// transmit stop condition
// leave with TWEA on for slave receiving
i2cSendStop();
while( !(inb(TWCR) & BV(TWSTO)) );
// enable TWI interrupt
sbi(TWCR, TWIE);
return retval;
}
u08 i2cMasterReceiveNI(u08 deviceAddr, u08 length, u08 *data)
{
u08 retval = I2C_OK;
// disable TWI interrupt
cbi(TWCR, TWIE);
// send start condition
i2cSendStart();
i2cWaitForComplete();
// send device address with read
i2cSendByte( deviceAddr | 0x01 );
i2cWaitForComplete();
// check if device is present and live
if( inb(TWSR) == TW_MR_SLA_ACK)
{
// accept receive data and ack it
while(length > 1)
{
i2cReceiveByte(TRUE);
i2cWaitForComplete();
*data++ = i2cGetReceivedByte();
// decrement length
length--;
}
// accept receive data and nack it (last-byte signal)
i2cReceiveByte(FALSE);
i2cWaitForComplete();
*data++ = i2cGetReceivedByte();
}
else
{
// device did not ACK it's address,
// data will not be transferred
// return error
retval = I2C_ERROR_NODEV;
}
// transmit stop condition
// leave with TWEA on for slave receiving
i2cSendStop();
// enable TWI interrupt
sbi(TWCR, TWIE);
return retval;
}
/*
void i2cMasterTransferNI(u08 deviceAddr, u08 sendlength, u08* senddata, u08 receivelength, u08* receivedata)
{
// disable TWI interrupt
cbi(TWCR, TWIE);
// send start condition
i2cSendStart();
i2cWaitForComplete();
// if there's data to be sent, do it
if(sendlength)
{
// send device address with write
i2cSendByte( deviceAddr & 0xFE );
i2cWaitForComplete();
// send data
while(sendlength)
{
i2cSendByte( *senddata++ );
i2cWaitForComplete();
sendlength--;
}
}
// if there's data to be received, do it
if(receivelength)
{
// send repeated start condition
i2cSendStart();
i2cWaitForComplete();
// send device address with read
i2cSendByte( deviceAddr | 0x01 );
i2cWaitForComplete();
// accept receive data and ack it
while(receivelength > 1)
{
i2cReceiveByte(TRUE);
i2cWaitForComplete();
*receivedata++ = i2cGetReceivedByte();
// decrement length
receivelength--;
}
// accept receive data and nack it (last-byte signal)
i2cReceiveByte(TRUE);
i2cWaitForComplete();
*receivedata++ = i2cGetReceivedByte();
}
// transmit stop condition
// leave with TWEA on for slave receiving
i2cSendStop();
while( !(inb(TWCR) & BV(TWSTO)) );
// enable TWI interrupt
sbi(TWCR, TWIE);
}
*/
//! I2C (TWI) interrupt service routine
SIGNAL(TWI_vect)
{
// read status bits
u08 status = inb(TWSR) & TWSR_STATUS_MASK;
switch(status)
{
// Master General
case TW_START: // 0x08: Sent start condition
case TW_REP_START: // 0x10: Sent repeated start condition
#ifdef I2C_DEBUG
putstring("I2C: M->START\r\n");
#endif
// send device address
i2cSendByte(I2cDeviceAddrRW);
break;
// Master Transmitter & Receiver status codes
case TW_MT_SLA_ACK: // 0x18: Slave address acknowledged
case TW_MT_DATA_ACK: // 0x28: Data acknowledged
#ifdef I2C_DEBUG
putstring("I2C: MT->SLA_ACK or DATA_ACK\r\n");
#endif
if(I2cSendDataIndex < I2cSendDataLength)
{
// send data
i2cSendByte( I2cSendData[I2cSendDataIndex++] );
}
else
{
// transmit stop condition, enable SLA ACK
i2cSendStop();
// set state
I2cState = I2C_IDLE;
}
break;
case TW_MR_DATA_NACK: // 0x58: Data received, NACK reply issued
#ifdef I2C_DEBUG
putstring("I2C: MR->DATA_NACK\r\n");
#endif
// store final received data byte
I2cReceiveData[I2cReceiveDataIndex++] = inb(TWDR);
// continue to transmit STOP condition
case TW_MR_SLA_NACK: // 0x48: Slave address not acknowledged
case TW_MT_SLA_NACK: // 0x20: Slave address not acknowledged
case TW_MT_DATA_NACK: // 0x30: Data not acknowledged
#ifdef I2C_DEBUG
putstring("I2C: MTR->SLA_NACK or MT->DATA_NACK\r\n");
#endif
// transmit stop condition, enable SLA ACK
i2cSendStop();
// set state
I2cState = I2C_IDLE;
break;
case TW_MT_ARB_LOST: // 0x38: Bus arbitration lost
//case TW_MR_ARB_LOST: // 0x38: Bus arbitration lost
#ifdef I2C_DEBUG
putstring("I2C: MT->ARB_LOST\r\n");
#endif
// release bus
outb(TWCR, (inb(TWCR)&TWCR_CMD_MASK)|BV(TWINT));
// set state
I2cState = I2C_IDLE;
// release bus and transmit start when bus is free
//outb(TWCR, (inb(TWCR)&TWCR_CMD_MASK)|BV(TWINT)|BV(TWSTA));
break;
case TW_MR_DATA_ACK: // 0x50: Data acknowledged
#ifdef I2C_DEBUG
putstring("I2C: MR->DATA_ACK\r\n");
#endif
// store received data byte
uint8_t x = inb(TWDR);
I2cReceiveData[I2cReceiveDataIndex++] = x;
uart_putw_hex(x);
// fall-through to see if more bytes will be received
case TW_MR_SLA_ACK: // 0x40: Slave address acknowledged
#ifdef I2C_DEBUG
putstring("I2C: MR->SLA_ACK\r\n");
#endif
if(I2cReceiveDataIndex < (I2cReceiveDataLength-1))
// data byte will be received, reply with ACK (more bytes in transfer)
i2cReceiveByte(TRUE);
else
// data byte will be received, reply with NACK (final byte in transfer)
i2cReceiveByte(FALSE);
break;
// Slave Receiver status codes
case TW_SR_SLA_ACK: // 0x60: own SLA+W has been received, ACK has been returned
case TW_SR_ARB_LOST_SLA_ACK: // 0x68: own SLA+W has been received, ACK has been returned
case TW_SR_GCALL_ACK: // 0x70: GCA+W has been received, ACK has been returned
case TW_SR_ARB_LOST_GCALL_ACK: // 0x78: GCA+W has been received, ACK has been returned
#ifdef I2C_DEBUG
putstring("I2C: SR->SLA_ACK\r\n");
#endif
// we are being addressed as slave for writing (data will be received from master)
// set state
I2cState = I2C_SLAVE_RX;
// prepare buffer
I2cReceiveDataIndex = 0;
// receive data byte and return ACK
outb(TWCR, (inb(TWCR)&TWCR_CMD_MASK)|BV(TWINT)|BV(TWEA));
break;
case TW_SR_DATA_ACK: // 0x80: data byte has been received, ACK has been returned
case TW_SR_GCALL_DATA_ACK: // 0x90: data byte has been received, ACK has been returned
#ifdef I2C_DEBUG
putstring("I2C: SR->DATA_ACK\r\n");
#endif
// get previously received data byte
I2cReceiveData[I2cReceiveDataIndex++] = inb(TWDR);
// check receive buffer status
if(I2cReceiveDataIndex < I2C_RECEIVE_DATA_BUFFER_SIZE)
{
// receive data byte and return ACK
i2cReceiveByte(TRUE);
//outb(TWCR, (inb(TWCR)&TWCR_CMD_MASK)|BV(TWINT)|BV(TWEA));
}
else
{
// receive data byte and return NACK
i2cReceiveByte(FALSE);
//outb(TWCR, (inb(TWCR)&TWCR_CMD_MASK)|BV(TWINT));
}
break;
case TW_SR_DATA_NACK: // 0x88: data byte has been received, NACK has been returned
case TW_SR_GCALL_DATA_NACK: // 0x98: data byte has been received, NACK has been returned
#ifdef I2C_DEBUG
putstring("I2C: SR->DATA_NACK\r\n");
#endif
// receive data byte and return NACK
i2cReceiveByte(FALSE);
//outb(TWCR, (inb(TWCR)&TWCR_CMD_MASK)|BV(TWINT));
break;
case TW_SR_STOP: // 0xA0: STOP or REPEATED START has been received while addressed as slave
#ifdef I2C_DEBUG
putstring("I2C: SR->SR_STOP\r\n");
#endif
// switch to SR mode with SLA ACK
outb(TWCR, (inb(TWCR)&TWCR_CMD_MASK)|BV(TWINT)|BV(TWEA));
// i2c receive is complete, call i2cSlaveReceive
if(i2cSlaveReceive) i2cSlaveReceive(I2cReceiveDataIndex, I2cReceiveData);
// set state
I2cState = I2C_IDLE;
break;
// Slave Transmitter
case TW_ST_SLA_ACK: // 0xA8: own SLA+R has been received, ACK has been returned
case TW_ST_ARB_LOST_SLA_ACK: // 0xB0: GCA+R has been received, ACK has been returned
#ifdef I2C_DEBUG
putstring("I2C: ST->SLA_ACK\r\n");
#endif
// we are being addressed as slave for reading (data must be transmitted back to master)
// set state
I2cState = I2C_SLAVE_TX;
// request data from application
if(i2cSlaveTransmit) I2cSendDataLength = i2cSlaveTransmit(I2C_SEND_DATA_BUFFER_SIZE, I2cSendData);
// reset data index
I2cSendDataIndex = 0;
// fall-through to transmit first data byte
case TW_ST_DATA_ACK: // 0xB8: data byte has been transmitted, ACK has been received
#ifdef I2C_DEBUG
putstring("I2C: ST->DATA_ACK\r\n");
#endif
// transmit data byte
outb(TWDR, I2cSendData[I2cSendDataIndex++]);
if(I2cSendDataIndex < I2cSendDataLength)
// expect ACK to data byte
outb(TWCR, (inb(TWCR)&TWCR_CMD_MASK)|BV(TWINT)|BV(TWEA));
else
// expect NACK to data byte
outb(TWCR, (inb(TWCR)&TWCR_CMD_MASK)|BV(TWINT));
break;
case TW_ST_DATA_NACK: // 0xC0: data byte has been transmitted, NACK has been received
case TW_ST_LAST_DATA: // 0xC8:
#ifdef I2C_DEBUG
putstring("I2C: ST->DATA_NACK or LAST_DATA\r\n");
#endif
// all done
// switch to open slave
outb(TWCR, (inb(TWCR)&TWCR_CMD_MASK)|BV(TWINT)|BV(TWEA));
// set state
I2cState = I2C_IDLE;
break;
// Misc
case TW_NO_INFO: // 0xF8: No relevant state information
// do nothing
#ifdef I2C_DEBUG
putstring("I2C: NO_INFO\r\n");
#endif
break;
case TW_BUS_ERROR: // 0x00: Bus error due to illegal start or stop condition
#ifdef I2C_DEBUG
putstring("I2C: BUS_ERROR\r\n");
#endif
// reset internal hardware and release bus
outb(TWCR, (inb(TWCR)&TWCR_CMD_MASK)|BV(TWINT)|BV(TWSTO)|BV(TWEA));
// set state
I2cState = I2C_IDLE;
break;
}
}
eI2cStateType i2cGetState(void)
{
return I2cState;
}