You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
480 lines
13 KiB
C
480 lines
13 KiB
C
/*
|
|
twi.c - TWI/I2C library for Wiring & Arduino
|
|
Copyright (c) 2006 Nicholas Zambetti. All right reserved.
|
|
|
|
This library is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU Lesser General Public
|
|
License as published by the Free Software Foundation; either
|
|
version 2.1 of the License, or (at your option) any later version.
|
|
|
|
This library 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
|
|
Lesser General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Lesser General Public
|
|
License along with this library; if not, write to the Free Software
|
|
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
|
|
*/
|
|
|
|
#include <math.h>
|
|
#include <stdlib.h>
|
|
#include <inttypes.h>
|
|
#include <avr/io.h>
|
|
#include <avr/interrupt.h>
|
|
#include <compat/twi.h>
|
|
|
|
#ifndef cbi
|
|
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
|
|
#endif
|
|
|
|
#ifndef sbi
|
|
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
|
|
#endif
|
|
|
|
#include "twi.h"
|
|
|
|
static volatile uint8_t twi_state;
|
|
static uint8_t twi_slarw;
|
|
|
|
static void (*twi_onSlaveTransmit)(void);
|
|
static void (*twi_onSlaveReceive)(uint8_t*, int);
|
|
|
|
static uint8_t* twi_masterBuffer;
|
|
static volatile uint8_t twi_masterBufferIndex;
|
|
static uint8_t twi_masterBufferLength;
|
|
|
|
static uint8_t* twi_txBuffer;
|
|
static volatile uint8_t twi_txBufferIndex;
|
|
static volatile uint8_t twi_txBufferLength;
|
|
|
|
static uint8_t* twi_rxBuffer;
|
|
static volatile uint8_t twi_rxBufferIndex;
|
|
|
|
static volatile uint8_t twi_error;
|
|
|
|
/*
|
|
* Function twi_init
|
|
* Desc readys twi pins and sets twi bitrate
|
|
* Input none
|
|
* Output none
|
|
*/
|
|
void twi_init(void)
|
|
{
|
|
// initialize state
|
|
twi_state = TWI_READY;
|
|
|
|
#if defined(__AVR_ATmega168__) || defined(__AVR_ATmega8__) || defined(__AVR_ATmega328P__)
|
|
// activate internal pull-ups for twi
|
|
// as per note from atmega8 manual pg167
|
|
sbi(PORTC, 4);
|
|
sbi(PORTC, 5);
|
|
#else
|
|
// activate internal pull-ups for twi
|
|
// as per note from atmega128 manual pg204
|
|
sbi(PORTD, 0);
|
|
sbi(PORTD, 1);
|
|
#endif
|
|
|
|
// initialize twi prescaler and bit rate
|
|
cbi(TWSR, TWPS0);
|
|
cbi(TWSR, TWPS1);
|
|
TWBR = ((CPU_FREQ / TWI_FREQ) - 16) / 2;
|
|
|
|
/* twi bit rate formula from atmega128 manual pg 204
|
|
SCL Frequency = CPU Clock Frequency / (16 + (2 * TWBR))
|
|
note: TWBR should be 10 or higher for master mode
|
|
It is 72 for a 16mhz Wiring board with 100kHz TWI */
|
|
|
|
// enable twi module, acks, and twi interrupt
|
|
TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA);
|
|
|
|
// allocate buffers
|
|
twi_masterBuffer = (uint8_t*) calloc(TWI_BUFFER_LENGTH, sizeof(uint8_t));
|
|
twi_txBuffer = (uint8_t*) calloc(TWI_BUFFER_LENGTH, sizeof(uint8_t));
|
|
twi_rxBuffer = (uint8_t*) calloc(TWI_BUFFER_LENGTH, sizeof(uint8_t));
|
|
}
|
|
|
|
/*
|
|
* Function twi_slaveInit
|
|
* Desc sets slave address and enables interrupt
|
|
* Input none
|
|
* Output none
|
|
*/
|
|
void twi_setAddress(uint8_t address)
|
|
{
|
|
// set twi slave address (skip over TWGCE bit)
|
|
TWAR = address << 1;
|
|
}
|
|
|
|
/*
|
|
* Function twi_readFrom
|
|
* Desc attempts to become twi bus master and read a
|
|
* series of bytes from a device on the bus
|
|
* Input address: 7bit i2c device address
|
|
* data: pointer to byte array
|
|
* length: number of bytes to read into array
|
|
* Output number of bytes read
|
|
*/
|
|
uint8_t twi_readFrom(uint8_t address, uint8_t* data, uint8_t length)
|
|
{
|
|
uint8_t i;
|
|
|
|
// ensure data will fit into buffer
|
|
if(TWI_BUFFER_LENGTH < length){
|
|
return 0;
|
|
}
|
|
|
|
// wait until twi is ready, become master receiver
|
|
while(TWI_READY != twi_state){
|
|
continue;
|
|
}
|
|
twi_state = TWI_MRX;
|
|
// reset error state (0xFF.. no error occured)
|
|
twi_error = 0xFF;
|
|
|
|
// initialize buffer iteration vars
|
|
twi_masterBufferIndex = 0;
|
|
twi_masterBufferLength = length-1; // This is not intuitive, read on...
|
|
// On receive, the previously configured ACK/NACK setting is transmitted in
|
|
// response to the received byte before the interrupt is signalled.
|
|
// Therefor we must actually set NACK when the _next_ to last byte is
|
|
// received, causing that NACK to be sent in response to receiving the last
|
|
// expected byte of data.
|
|
|
|
// build sla+w, slave device address + w bit
|
|
twi_slarw = TW_READ;
|
|
twi_slarw |= address << 1;
|
|
|
|
// send start condition
|
|
TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT) | _BV(TWSTA);
|
|
|
|
// wait for read operation to complete
|
|
while(TWI_MRX == twi_state){
|
|
continue;
|
|
}
|
|
|
|
if (twi_masterBufferIndex < length)
|
|
length = twi_masterBufferIndex;
|
|
|
|
// copy twi buffer to data
|
|
for(i = 0; i < length; ++i){
|
|
data[i] = twi_masterBuffer[i];
|
|
}
|
|
|
|
return length;
|
|
}
|
|
|
|
/*
|
|
* Function twi_writeTo
|
|
* Desc attempts to become twi bus master and write a
|
|
* series of bytes to a device on the bus
|
|
* Input address: 7bit i2c device address
|
|
* data: pointer to byte array
|
|
* length: number of bytes in array
|
|
* wait: boolean indicating to wait for write or not
|
|
* Output 0 .. success
|
|
* 1 .. length to long for buffer
|
|
* 2 .. address send, NACK received
|
|
* 3 .. data send, NACK received
|
|
* 4 .. other twi error (lost bus arbitration, bus error, ..)
|
|
*/
|
|
uint8_t twi_writeTo(uint8_t address, uint8_t* data, uint8_t length, uint8_t wait)
|
|
{
|
|
uint8_t i;
|
|
|
|
// ensure data will fit into buffer
|
|
if(TWI_BUFFER_LENGTH < length){
|
|
return 1;
|
|
}
|
|
|
|
// wait until twi is ready, become master transmitter
|
|
while(TWI_READY != twi_state){
|
|
continue;
|
|
}
|
|
twi_state = TWI_MTX;
|
|
// reset error state (0xFF.. no error occured)
|
|
twi_error = 0xFF;
|
|
|
|
// initialize buffer iteration vars
|
|
twi_masterBufferIndex = 0;
|
|
twi_masterBufferLength = length;
|
|
|
|
// copy data to twi buffer
|
|
for(i = 0; i < length; ++i){
|
|
twi_masterBuffer[i] = data[i];
|
|
}
|
|
|
|
// build sla+w, slave device address + w bit
|
|
twi_slarw = TW_WRITE;
|
|
twi_slarw |= address << 1;
|
|
|
|
// send start condition
|
|
TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT) | _BV(TWSTA);
|
|
|
|
// wait for write operation to complete
|
|
while(wait && (TWI_MTX == twi_state)){
|
|
continue;
|
|
}
|
|
|
|
if (twi_error == 0xFF)
|
|
return 0; // success
|
|
else if (twi_error == TW_MT_SLA_NACK)
|
|
return 2; // error: address send, nack received
|
|
else if (twi_error == TW_MT_DATA_NACK)
|
|
return 3; // error: data send, nack received
|
|
else
|
|
return 4; // other twi error
|
|
}
|
|
|
|
/*
|
|
* Function twi_transmit
|
|
* Desc fills slave tx buffer with data
|
|
* must be called in slave tx event callback
|
|
* Input data: pointer to byte array
|
|
* length: number of bytes in array
|
|
* Output 1 length too long for buffer
|
|
* 2 not slave transmitter
|
|
* 0 ok
|
|
*/
|
|
uint8_t twi_transmit(uint8_t* data, uint8_t length)
|
|
{
|
|
uint8_t i;
|
|
|
|
// ensure data will fit into buffer
|
|
if(TWI_BUFFER_LENGTH < length){
|
|
return 1;
|
|
}
|
|
|
|
// ensure we are currently a slave transmitter
|
|
if(TWI_STX != twi_state){
|
|
return 2;
|
|
}
|
|
|
|
// set length and copy data into tx buffer
|
|
twi_txBufferLength = length;
|
|
for(i = 0; i < length; ++i){
|
|
twi_txBuffer[i] = data[i];
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Function twi_attachSlaveRxEvent
|
|
* Desc sets function called before a slave read operation
|
|
* Input function: callback function to use
|
|
* Output none
|
|
*/
|
|
void twi_attachSlaveRxEvent( void (*function)(uint8_t*, int) )
|
|
{
|
|
twi_onSlaveReceive = function;
|
|
}
|
|
|
|
/*
|
|
* Function twi_attachSlaveTxEvent
|
|
* Desc sets function called before a slave write operation
|
|
* Input function: callback function to use
|
|
* Output none
|
|
*/
|
|
void twi_attachSlaveTxEvent( void (*function)(void) )
|
|
{
|
|
twi_onSlaveTransmit = function;
|
|
}
|
|
|
|
/*
|
|
* Function twi_reply
|
|
* Desc sends byte or readys receive line
|
|
* Input ack: byte indicating to ack or to nack
|
|
* Output none
|
|
*/
|
|
void twi_reply(uint8_t ack)
|
|
{
|
|
// transmit master read ready signal, with or without ack
|
|
if(ack){
|
|
TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWINT) | _BV(TWEA);
|
|
}else{
|
|
TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWINT);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Function twi_stop
|
|
* Desc relinquishes bus master status
|
|
* Input none
|
|
* Output none
|
|
*/
|
|
void twi_stop(void)
|
|
{
|
|
// send stop condition
|
|
TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT) | _BV(TWSTO);
|
|
|
|
// wait for stop condition to be exectued on bus
|
|
// TWINT is not set after a stop condition!
|
|
while(TWCR & _BV(TWSTO)){
|
|
continue;
|
|
}
|
|
|
|
// update twi state
|
|
twi_state = TWI_READY;
|
|
}
|
|
|
|
/*
|
|
* Function twi_releaseBus
|
|
* Desc releases bus control
|
|
* Input none
|
|
* Output none
|
|
*/
|
|
void twi_releaseBus(void)
|
|
{
|
|
// release bus
|
|
TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT);
|
|
|
|
// update twi state
|
|
twi_state = TWI_READY;
|
|
}
|
|
|
|
SIGNAL(TWI_vect)
|
|
{
|
|
switch(TW_STATUS){
|
|
// All Master
|
|
case TW_START: // sent start condition
|
|
case TW_REP_START: // sent repeated start condition
|
|
// copy device address and r/w bit to output register and ack
|
|
TWDR = twi_slarw;
|
|
twi_reply(1);
|
|
break;
|
|
|
|
// Master Transmitter
|
|
case TW_MT_SLA_ACK: // slave receiver acked address
|
|
case TW_MT_DATA_ACK: // slave receiver acked data
|
|
// if there is data to send, send it, otherwise stop
|
|
if(twi_masterBufferIndex < twi_masterBufferLength){
|
|
// copy data to output register and ack
|
|
TWDR = twi_masterBuffer[twi_masterBufferIndex++];
|
|
twi_reply(1);
|
|
}else{
|
|
twi_stop();
|
|
}
|
|
break;
|
|
case TW_MT_SLA_NACK: // address sent, nack received
|
|
twi_error = TW_MT_SLA_NACK;
|
|
twi_stop();
|
|
break;
|
|
case TW_MT_DATA_NACK: // data sent, nack received
|
|
twi_error = TW_MT_DATA_NACK;
|
|
twi_stop();
|
|
break;
|
|
case TW_MT_ARB_LOST: // lost bus arbitration
|
|
twi_error = TW_MT_ARB_LOST;
|
|
twi_releaseBus();
|
|
break;
|
|
|
|
// Master Receiver
|
|
case TW_MR_DATA_ACK: // data received, ack sent
|
|
// put byte into buffer
|
|
twi_masterBuffer[twi_masterBufferIndex++] = TWDR;
|
|
case TW_MR_SLA_ACK: // address sent, ack received
|
|
// ack if more bytes are expected, otherwise nack
|
|
if(twi_masterBufferIndex < twi_masterBufferLength){
|
|
twi_reply(1);
|
|
}else{
|
|
twi_reply(0);
|
|
}
|
|
break;
|
|
case TW_MR_DATA_NACK: // data received, nack sent
|
|
// put final byte into buffer
|
|
twi_masterBuffer[twi_masterBufferIndex++] = TWDR;
|
|
case TW_MR_SLA_NACK: // address sent, nack received
|
|
twi_stop();
|
|
break;
|
|
// TW_MR_ARB_LOST handled by TW_MT_ARB_LOST case
|
|
|
|
// Slave Receiver
|
|
case TW_SR_SLA_ACK: // addressed, returned ack
|
|
case TW_SR_GCALL_ACK: // addressed generally, returned ack
|
|
case TW_SR_ARB_LOST_SLA_ACK: // lost arbitration, returned ack
|
|
case TW_SR_ARB_LOST_GCALL_ACK: // lost arbitration, returned ack
|
|
// enter slave receiver mode
|
|
twi_state = TWI_SRX;
|
|
// indicate that rx buffer can be overwritten and ack
|
|
twi_rxBufferIndex = 0;
|
|
twi_reply(1);
|
|
break;
|
|
case TW_SR_DATA_ACK: // data received, returned ack
|
|
case TW_SR_GCALL_DATA_ACK: // data received generally, returned ack
|
|
// if there is still room in the rx buffer
|
|
if(twi_rxBufferIndex < TWI_BUFFER_LENGTH){
|
|
// put byte in buffer and ack
|
|
twi_rxBuffer[twi_rxBufferIndex++] = TWDR;
|
|
twi_reply(1);
|
|
}else{
|
|
// otherwise nack
|
|
twi_reply(0);
|
|
}
|
|
break;
|
|
case TW_SR_STOP: // stop or repeated start condition received
|
|
// put a null char after data if there's room
|
|
if(twi_rxBufferIndex < TWI_BUFFER_LENGTH){
|
|
twi_rxBuffer[twi_rxBufferIndex] = '\0';
|
|
}
|
|
// callback to user defined callback
|
|
twi_onSlaveReceive(twi_rxBuffer, twi_rxBufferIndex);
|
|
// ack future responses
|
|
twi_reply(1);
|
|
// leave slave receiver state
|
|
twi_state = TWI_READY;
|
|
break;
|
|
case TW_SR_DATA_NACK: // data received, returned nack
|
|
case TW_SR_GCALL_DATA_NACK: // data received generally, returned nack
|
|
// nack back at master
|
|
twi_reply(0);
|
|
break;
|
|
|
|
// Slave Transmitter
|
|
case TW_ST_SLA_ACK: // addressed, returned ack
|
|
case TW_ST_ARB_LOST_SLA_ACK: // arbitration lost, returned ack
|
|
// enter slave transmitter mode
|
|
twi_state = TWI_STX;
|
|
// ready the tx buffer index for iteration
|
|
twi_txBufferIndex = 0;
|
|
// set tx buffer length to be zero, to verify if user changes it
|
|
twi_txBufferLength = 0;
|
|
// request for txBuffer to be filled and length to be set
|
|
// note: user must call twi_transmit(bytes, length) to do this
|
|
twi_onSlaveTransmit();
|
|
// if they didn't change buffer & length, initialize it
|
|
if(0 == twi_txBufferLength){
|
|
twi_txBufferLength = 1;
|
|
twi_txBuffer[0] = 0x00;
|
|
}
|
|
// transmit first byte from buffer, fall
|
|
case TW_ST_DATA_ACK: // byte sent, ack returned
|
|
// copy data to output register
|
|
TWDR = twi_txBuffer[twi_txBufferIndex++];
|
|
// if there is more to send, ack, otherwise nack
|
|
if(twi_txBufferIndex < twi_txBufferLength){
|
|
twi_reply(1);
|
|
}else{
|
|
twi_reply(0);
|
|
}
|
|
break;
|
|
case TW_ST_DATA_NACK: // received nack, we are done
|
|
case TW_ST_LAST_DATA: // received ack, but we are done already!
|
|
// ack future responses
|
|
twi_reply(1);
|
|
// leave slave receiver state
|
|
twi_state = TWI_READY;
|
|
break;
|
|
|
|
// All
|
|
case TW_NO_INFO: // no state information
|
|
break;
|
|
case TW_BUS_ERROR: // bus error, illegal stop/start
|
|
twi_error = TW_BUS_ERROR;
|
|
twi_stop();
|
|
break;
|
|
}
|
|
}
|
|
|