| /* |
| 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[TWI_BUFFER_LENGTH]; |
| static volatile uint8_t twi_masterBufferIndex; |
| static uint8_t twi_masterBufferLength; |
| |
| static uint8_t twi_txBuffer[TWI_BUFFER_LENGTH]; |
| static volatile uint8_t twi_txBufferIndex; |
| static volatile uint8_t twi_txBufferLength; |
| |
| static uint8_t twi_rxBuffer[TWI_BUFFER_LENGTH]; |
| 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); |
| } |
| |
| /* |
| * 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'; |
| } |
| // sends ack and stops interface for clock stretching |
| twi_stop(); |
| // callback to user defined callback |
| twi_onSlaveReceive(twi_rxBuffer, twi_rxBufferIndex); |
| // since we submit rx buffer to "wire" library, we can reset it |
| twi_rxBufferIndex = 0; |
| // ack future responses and leave slave receiver state |
| twi_releaseBus(); |
| 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; |
| } |
| } |
| |