diff options
Diffstat (limited to 'libraries/Wire/utility')
| -rw-r--r-- | libraries/Wire/utility/twi.c | 527 | ||||
| -rwxr-xr-x | libraries/Wire/utility/twi.h | 53 |
2 files changed, 580 insertions, 0 deletions
diff --git a/libraries/Wire/utility/twi.c b/libraries/Wire/utility/twi.c new file mode 100644 index 0000000..6b2db3c --- /dev/null +++ b/libraries/Wire/utility/twi.c @@ -0,0 +1,527 @@ +/* + 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 + + Modified 2012 by Todd Krein (todd@krein.org) to implement repeated starts +*/ + +#include <math.h> +#include <stdlib.h> +#include <inttypes.h> +#include <avr/io.h> +#include <avr/interrupt.h> +#include <compat/twi.h> +#include "Arduino.h" // for digitalWrite + +#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 "pins_arduino.h" +#include "twi.h" + +static volatile uint8_t twi_state; +static volatile uint8_t twi_slarw; +static volatile uint8_t twi_sendStop; // should the transaction end with a stop +static volatile uint8_t twi_inRepStart; // in the middle of a repeated start + +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 volatile 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; + twi_sendStop = true; // default value + twi_inRepStart = false; + + // activate internal pullups for twi. + digitalWrite(SDA, 1); + digitalWrite(SCL, 1); + + // initialize twi prescaler and bit rate + cbi(TWSR, TWPS0); + cbi(TWSR, TWPS1); + TWBR = ((F_CPU / 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 + * sendStop: Boolean indicating whether to send a stop at the end + * Output number of bytes read + */ +uint8_t twi_readFrom(uint8_t address, uint8_t* data, uint8_t length, uint8_t sendStop) +{ + 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; + twi_sendStop = sendStop; + // 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; + + if (true == twi_inRepStart) { + // if we're in the repeated start state, then we've already sent the start, + // (@@@ we hope), and the TWI statemachine is just waiting for the address byte. + // We need to remove ourselves from the repeated start state before we enable interrupts, + // since the ISR is ASYNC, and we could get confused if we hit the ISR before cleaning + // up. Also, don't enable the START interrupt. There may be one pending from the + // repeated start that we sent outselves, and that would really confuse things. + twi_inRepStart = false; // remember, we're dealing with an ASYNC ISR + TWDR = twi_slarw; + TWCR = _BV(TWINT) | _BV(TWEA) | _BV(TWEN) | _BV(TWIE); // enable INTs, but not START + } + else + // 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 + * sendStop: boolean indicating whether or not to send a stop at the end + * 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 sendStop) +{ + 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; + twi_sendStop = sendStop; + // 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; + + // if we're in a repeated start, then we've already sent the START + // in the ISR. Don't do it again. + // + if (true == twi_inRepStart) { + // if we're in the repeated start state, then we've already sent the start, + // (@@@ we hope), and the TWI statemachine is just waiting for the address byte. + // We need to remove ourselves from the repeated start state before we enable interrupts, + // since the ISR is ASYNC, and we could get confused if we hit the ISR before cleaning + // up. Also, don't enable the START interrupt. There may be one pending from the + // repeated start that we sent outselves, and that would really confuse things. + twi_inRepStart = false; // remember, we're dealing with an ASYNC ISR + TWDR = twi_slarw; + TWCR = _BV(TWINT) | _BV(TWEA) | _BV(TWEN) | _BV(TWIE); // enable INTs, but not START + } + else + // send start condition + TWCR = _BV(TWINT) | _BV(TWEA) | _BV(TWEN) | _BV(TWIE) | _BV(TWSTA); // enable INTs + + // 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(const 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{ + if (twi_sendStop) + twi_stop(); + else { + twi_inRepStart = true; // we're gonna send the START + // don't enable the interrupt. We'll generate the start, but we + // avoid handling the interrupt until we're in the next transaction, + // at the point where we would normally issue the start. + TWCR = _BV(TWINT) | _BV(TWSTA)| _BV(TWEN) ; + twi_state = TWI_READY; + } + } + 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; + if (twi_sendStop) + twi_stop(); + else { + twi_inRepStart = true; // we're gonna send the START + // don't enable the interrupt. We'll generate the start, but we + // avoid handling the interrupt until we're in the next transaction, + // at the point where we would normally issue the start. + TWCR = _BV(TWINT) | _BV(TWSTA)| _BV(TWEN) ; + twi_state = TWI_READY; + } + break; + 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; + } +} + diff --git a/libraries/Wire/utility/twi.h b/libraries/Wire/utility/twi.h new file mode 100755 index 0000000..6526593 --- /dev/null +++ b/libraries/Wire/utility/twi.h @@ -0,0 +1,53 @@ +/* + twi.h - 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 +*/ + +#ifndef twi_h +#define twi_h + + #include <inttypes.h> + + //#define ATMEGA8 + + #ifndef TWI_FREQ + #define TWI_FREQ 100000L + #endif + + #ifndef TWI_BUFFER_LENGTH + #define TWI_BUFFER_LENGTH 32 + #endif + + #define TWI_READY 0 + #define TWI_MRX 1 + #define TWI_MTX 2 + #define TWI_SRX 3 + #define TWI_STX 4 + + void twi_init(void); + void twi_setAddress(uint8_t); + uint8_t twi_readFrom(uint8_t, uint8_t*, uint8_t, uint8_t); + uint8_t twi_writeTo(uint8_t, uint8_t*, uint8_t, uint8_t, uint8_t); + uint8_t twi_transmit(const uint8_t*, uint8_t); + void twi_attachSlaveRxEvent( void (*)(uint8_t*, int) ); + void twi_attachSlaveTxEvent( void (*)(void) ); + void twi_reply(uint8_t); + void twi_stop(void); + void twi_releaseBus(void); + +#endif + |