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CommandStation-EX/I2CManager_AVR.h
Neil McKechnie cb287f23a4 I2CManager: Add support for I2C Multiplexers to Wire and AVR. 
AVR Native (non-blocking) driver now supports up to 8 I2C Multiplexers, as does any controller that uses Wire for I2C.
Other native drivers will be updated in due course.
2023-02-07 16:38:30 +00:00

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/*
* © 2023, Neil McKechnie. All rights reserved.
*
* This file is part of CommandStation-EX
*
* This is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* It is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with CommandStation. If not, see <https://www.gnu.org/licenses/>.
*/
#ifndef I2CMANAGER_AVR_H
#define I2CMANAGER_AVR_H
#include <Arduino.h>
#include "I2CManager.h"
#include <avr/io.h>
#include <avr/interrupt.h>
/****************************************************************************
TWI State codes
****************************************************************************/
// General TWI Master staus codes
#define TWI_START 0x08 // START has been transmitted
#define TWI_REP_START 0x10 // Repeated START has been transmitted
#define TWI_ARB_LOST 0x38 // Arbitration lost
// TWI Master Transmitter staus codes
#define TWI_MTX_ADR_ACK 0x18 // SLA+W has been tramsmitted and ACK received
#define TWI_MTX_ADR_NACK 0x20 // SLA+W has been tramsmitted and NACK received
#define TWI_MTX_DATA_ACK 0x28 // Data byte has been tramsmitted and ACK received
#define TWI_MTX_DATA_NACK 0x30 // Data byte has been tramsmitted and NACK received
// TWI Master Receiver staus codes
#define TWI_MRX_ADR_ACK 0x40 // SLA+R has been tramsmitted and ACK received
#define TWI_MRX_ADR_NACK 0x48 // SLA+R has been tramsmitted and NACK received
#define TWI_MRX_DATA_ACK 0x50 // Data byte has been received and ACK tramsmitted
#define TWI_MRX_DATA_NACK 0x58 // Data byte has been received and NACK tramsmitted
// TWI Miscellaneous status codes
#define TWI_NO_STATE 0xF8 // No relevant state information available
#define TWI_BUS_ERROR 0x00 // Bus error due to an illegal START or STOP condition
#define TWI_TWBR ((F_CPU / I2C_FREQ) - 16) / 2 // TWI Bit rate Register setting.
#if defined(I2C_USE_INTERRUPTS)
#define ENABLE_TWI_INTERRUPT (1<<TWIE)
#else
#define ENABLE_TWI_INTERRUPT 0
#endif
/***************************************************************************
* Set I2C clock speed register.
***************************************************************************/
void I2CManagerClass::I2C_setClock(unsigned long i2cClockSpeed) {
unsigned long temp = ((F_CPU / i2cClockSpeed) - 16) / 2;
for (uint8_t preScaler = 0; preScaler<=3; preScaler++) {
if (temp <= 255) {
TWBR = temp;
TWSR = (TWSR & 0xfc) | preScaler;
return;
} else
temp /= 4;
}
// Set slowest speed ~= 500 bits/sec
TWBR = 255;
TWSR |= 0x03;
}
/***************************************************************************
* Initialise I2C registers.
***************************************************************************/
void I2CManagerClass::I2C_init()
{
TWSR = 0;
TWBR = TWI_TWBR; // Set bit rate register (Baudrate). Defined in header file.
TWDR = 0xFF; // Default content = SDA released.
TWCR = (1<<TWINT); // Clear interrupt flag
pinMode(SDA, INPUT_PULLUP);
pinMode(SCL, INPUT_PULLUP);
}
/***************************************************************************
* Initiate a start bit for transmission.
***************************************************************************/
void I2CManagerClass::I2C_sendStart() {
bytesToSend = currentRequest->writeLen;
bytesToReceive = currentRequest->readLen;
rxCount = 0;
txCount = 0;
#if defined(I2C_EXTENDED_ADDRESS)
if (currentRequest->i2cAddress.muxNumber() != I2CMux_None) {
// Send request to multiplexer
muxPhase = MuxPhase_PROLOG; // When start bit interrupt comes in, send SLA+W to MUX
} else
muxPhase = 0;
#endif
TWCR = (1<<TWEN)|ENABLE_TWI_INTERRUPT|(1<<TWINT)|(1<<TWEA)|(1<<TWSTA); // Send Start
}
/***************************************************************************
* Initiate a stop bit for transmission (does not interrupt)
***************************************************************************/
void I2CManagerClass::I2C_sendStop() {
TWDR = 0xff; // Default condition = SDA released
TWCR = (1<<TWEN)|(1<<TWINT)|(1<<TWSTO); // Send Stop
}
/***************************************************************************
* Close I2C down
***************************************************************************/
void I2CManagerClass::I2C_close() {
// disable TWI
TWCR = (1<<TWINT); // clear any interrupt and stop twi.
delayMicroseconds(10); // Wait for things to stabilise (hopefully)
}
/***************************************************************************
* Main state machine for I2C, called from interrupt handler or,
* if I2C_USE_INTERRUPTS isn't defined, from the I2CManagerClass::loop() function
* (and therefore, indirectly, from I2CRB::wait() and I2CRB::isBusy()).
***************************************************************************/
void I2CManagerClass::I2C_handleInterrupt() {
if (!(TWCR & (1<<TWINT))) return; // Nothing to do.
uint8_t twsr = TWSR & 0xF8;
#if defined(I2C_EXTENDED_ADDRESS)
// First process the MUX state machine.
// This does not need to be entered during passthru phase unless the
// application's send and receive have both completed.
if (muxPhase > MuxPhase_OFF && !(muxPhase==MuxPhase_PASSTHRU && (bytesToSend || bytesToReceive))) {
switch (twsr) {
case TWI_MTX_ADR_ACK: // SLA+W has been transmitted and ACK received
if (muxPhase == MuxPhase_PROLOG) {
// Send MUX selecter mask to follow address
I2CSubBus subBus = currentRequest->i2cAddress.subBus();
TWDR = (subBus==SubBus_All) ? 0xff :
(subBus==SubBus_None) ? 0x00 :
1 << subBus;
TWCR = (1<<TWEN)|ENABLE_TWI_INTERRUPT|(1<<TWINT);
return;
} else if (muxPhase == MuxPhase_EPILOG) {
TWDR = 0x00; // Disable all subbuses
TWCR = (1<<TWEN)|ENABLE_TWI_INTERRUPT|(1<<TWINT);
return;
}
break;
case TWI_MTX_DATA_ACK: // Data byte has been transmitted and ACK received
if (muxPhase == MuxPhase_PASSTHRU && !bytesToSend && !bytesToReceive) {
if (_muxCount > 1) {
// Device transaction complete, prepare to deselect MUX by sending start bit
TWCR = (1<<TWEN)|ENABLE_TWI_INTERRUPT|(1<<TWINT)|(1<<TWSTO)|(1<<TWSTA);
muxPhase = MuxPhase_EPILOG;
return;
} else {
// Only one MUX so no need to deselect it. Just finish off
TWCR = (1<<TWEN)|(1<<TWINT)|(1<<TWSTO);
state = I2C_STATE_COMPLETED;
muxPhase = MuxPhase_OFF;
return;
}
} else if (muxPhase == MuxPhase_PROLOG) {
// If device address is zero, then finish here (i.e. send mux subBus mask only)
if (currentRequest->i2cAddress.deviceAddress() == 0) {
// Send stop and post rb.
TWDR = 0xff;
TWCR = (1<<TWEN)|(1<<TWINT)|(1<<TWSTO);
state = I2C_STATE_COMPLETED;
muxPhase = MuxPhase_OFF;
return;
} else {
// Send stop followed by start, preparing to send device address
TWCR = (1<<TWEN)|ENABLE_TWI_INTERRUPT|(1<<TWINT)|(1<<TWSTO)|(1<<TWSTA);
muxPhase = MuxPhase_PASSTHRU;
return;
}
} else if (muxPhase == MuxPhase_EPILOG) {
// Send stop and allow RB to be posted.
TWDR = 0xff;
TWCR = (1<<TWEN)|(1<<TWINT)|(1<<TWSTO);
state = I2C_STATE_COMPLETED;
muxPhase = MuxPhase_OFF;
return;
}
break;
case TWI_MRX_DATA_NACK: // Last data byte has been received and NACK transmitted
// We must read the data before processing the MUX, so do this here.
if (bytesToReceive > 0) {
currentRequest->readBuffer[rxCount++] = TWDR;
bytesToReceive--;
}
if (muxPhase == MuxPhase_PASSTHRU && _muxCount > 1) {
// Prepare to transmit epilog to mux - first send the stop bit and start bit
// (we don't need to reset mux if there is only one.
TWCR = (1<<TWEN)|ENABLE_TWI_INTERRUPT|(1<<TWINT)|(1<<TWSTO)|(1<<TWSTA);
muxPhase = MuxPhase_EPILOG;
return;
} else {
// Finish up.
TWCR = (1<<TWEN)|(1<<TWINT)|(1<<TWSTO); // Send Stop
state = I2C_STATE_COMPLETED;
muxPhase = MuxPhase_OFF;
return;
}
break;
case TWI_START: // START has been transmitted
case TWI_REP_START: // Repeated START has been transmitted
if (muxPhase == MuxPhase_PROLOG || muxPhase == MuxPhase_EPILOG) {
// Send multiplexer address first
uint8_t muxAddress = I2C_MUX_BASE_ADDRESS + currentRequest->i2cAddress.muxNumber();
TWDR = (muxAddress << 1) | 0; // MUXaddress+Write
TWCR = (1<<TWEN)|ENABLE_TWI_INTERRUPT|(1<<TWINT);
return;
}
break;
case TWI_MTX_ADR_NACK: // SLA+W has been transmitted and NACK received
case TWI_MRX_ADR_NACK: // SLA+R has been transmitted and NACK received
case TWI_MTX_DATA_NACK: // Data byte has been transmitted and NACK received
if (muxPhase == MuxPhase_PASSTHRU) {
// Data transaction was nak'd, update RB status but continue with mux cleardown
completionStatus = I2C_STATUS_NEGATIVE_ACKNOWLEDGE;
TWCR = (1<<TWEN)|ENABLE_TWI_INTERRUPT|(1<<TWINT)|(1<<TWSTO)|(1<<TWSTA); // Send Stop and start
muxPhase = MuxPhase_EPILOG;
return;
} else if (muxPhase > MuxPhase_EPILOG) {
// Mux Cleardown was NAK'd, send stop and then finish.
TWCR = (1<<TWEN)|(1<<TWINT)|(1<<TWSTO); // Send Stop
state = I2C_STATE_COMPLETED;
return;
}
break;
}
}
#endif
// Now the main I2C interrupt handler, used for the device communications.
//
// Cases are ordered so that the most frequently used ones are tested first.
switch (twsr) {
case TWI_MTX_DATA_ACK: // Data byte has been transmitted and ACK received
case TWI_MTX_ADR_ACK: // SLA+W has been transmitted and ACK received
if (bytesToSend) { // Send first.
if (operation == OPERATION_SEND_P)
TWDR = GETFLASH(currentRequest->writeBuffer + (txCount++));
else
TWDR = currentRequest->writeBuffer[txCount++];
bytesToSend--;
TWCR = (1<<TWEN)|ENABLE_TWI_INTERRUPT|(1<<TWINT);
} else if (bytesToReceive) { // All sent, anything to receive?
// Don't need to wait for stop, as the interface won't send the start until
// any in-progress stop condition has been sent.
TWCR = (1<<TWEN)|ENABLE_TWI_INTERRUPT|(1<<TWINT)|(1<<TWSTA); // Send Start
} else {
// Nothing left to send or receive
TWCR = (1<<TWEN)|(1<<TWINT)|(1<<TWEA)|(1<<TWSTO); // Send Stop
state = I2C_STATE_COMPLETED;
}
break;
case TWI_MRX_DATA_ACK: // Data byte has been received and ACK transmitted
if (bytesToReceive > 0) {
currentRequest->readBuffer[rxCount++] = TWDR;
bytesToReceive--;
}
/* fallthrough */
case TWI_MRX_ADR_ACK: // SLA+R has been sent and ACK received
if (bytesToReceive <= 1) {
TWCR = (1<<TWEN)|ENABLE_TWI_INTERRUPT|(1<<TWINT); // Send NACK after next reception
} else {
// send ack
TWCR = (1<<TWEN)|ENABLE_TWI_INTERRUPT|(1<<TWINT)|(1<<TWEA);
}
break;
case TWI_MRX_DATA_NACK: // Data byte has been received and NACK transmitted
if (bytesToReceive > 0) {
currentRequest->readBuffer[rxCount++] = TWDR;
bytesToReceive--;
}
TWCR = (1<<TWEN)|(1<<TWINT)|(1<<TWEA)|(1<<TWSTO); // Send Stop
state = I2C_STATE_COMPLETED;
break;
case TWI_START: // START has been transmitted
case TWI_REP_START: // Repeated START has been transmitted
{
// Set up address and R/W
uint8_t deviceAddress = currentRequest->i2cAddress;
if (operation == OPERATION_READ || (operation==OPERATION_REQUEST && !bytesToSend))
TWDR = (deviceAddress << 1) | 1; // SLA+R
else
TWDR = (deviceAddress << 1) | 0; // SLA+W
TWCR = (1<<TWEN)|ENABLE_TWI_INTERRUPT|(1<<TWINT)|(1<<TWEA);
}
break;
case TWI_MTX_ADR_NACK: // SLA+W has been transmitted and NACK received
case TWI_MRX_ADR_NACK: // SLA+R has been transmitted and NACK received
case TWI_MTX_DATA_NACK: // Data byte has been transmitted and NACK received
TWCR = (1<<TWEN)|(1<<TWINT)|(1<<TWEA)|(1<<TWSTO); // Send Stop
completionStatus = I2C_STATUS_NEGATIVE_ACKNOWLEDGE;
state = I2C_STATE_COMPLETED;
break;
case TWI_ARB_LOST: // Arbitration lost
// Restart transaction from start.
I2C_sendStart();
break;
case TWI_BUS_ERROR: // Bus error due to an illegal START or STOP condition
default:
TWDR = 0xff; // Default condition = SDA released
TWCR = (1<<TWEN)|(1<<TWINT)|(1<<TWEA)|(1<<TWSTO); // Send Stop
completionStatus = I2C_STATUS_TRANSMIT_ERROR;
state = I2C_STATE_COMPLETED;
}
}
#if defined(I2C_USE_INTERRUPTS)
ISR(TWI_vect) {
I2CManagerClass::handleInterrupt();
}
#endif
#endif /* I2CMANAGER_AVR_H */
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