Include initial implementation based on Arduino's twi

Firmware/config.h

@@ -31,8 +31,8 @@
 
 //PAT9125 configuration
 //#define PAT9125_SWSPI
-#define PAT9125_SWI2C
-//#define PAT9125_I2C
+//#define PAT9125_SWI2C
+#define PAT9125_I2C
 
 #define PAT9125_I2C_ADDR  0x75  //ID=LO
 //#define PAT9125_I2C_ADDR  0x79  //ID=HI

Firmware/pat9125.c

@@ -31,7 +31,7 @@
 #elif defined(PAT9125_SWI2C)
 #include "swi2c.h"
 #elif defined(PAT9125_I2C)
-#error not implemented
+#include "twi.h"
 #else
 #error unknown PAT9125 communication method
 #endif
@@ -253,39 +253,48 @@ uint8_t pat9125_update_bs(void)
 uint8_t pat9125_rd_reg(uint8_t addr)
 {
 	uint8_t data = 0;
-#ifdef PAT9125_SWSPI
+#if defined(PAT9125_SWSPI)
 	swspi_start();
 	swspi_tx(addr & 0x7f);
 	data = swspi_rx();
 	swspi_stop();
-#endif //PAT9125_SWSPI
-#ifdef PAT9125_SWI2C
+#elif defined(PAT9125_SWI2C)
 	if (!swi2c_readByte_A8(PAT9125_I2C_ADDR, addr, &data)) //NO ACK error
-	{
-		pat9125_PID1 = 0xff;
-		pat9125_PID2 = 0xff;
-		return 0;
-	}
-#endif //PAT9125_SWI2C
+        goto error;
+#elif defined(PAT9125_I2C)
+	if (twi_writeTo(PAT9125_I2C_ADDR,&addr,1,1,0) != 0 ||
+        twi_readFrom(PAT9125_I2C_ADDR,&data,1,1) != 1)
+        goto error;
+#endif
 	return data;
+
+ error:
+    pat9125_PID1 = 0xff;
+    pat9125_PID2 = 0xff;
+    return 0;
 }
 
 void pat9125_wr_reg(uint8_t addr, uint8_t data)
 {
-#ifdef PAT9125_SWSPI
+#if defined(PAT9125_SWSPI)
 	swspi_start();
 	swspi_tx(addr | 0x80);
 	swspi_tx(data);
 	swspi_stop();
-#endif //PAT9125_SWSPI
-#ifdef PAT9125_SWI2C
+#elif defined(PAT9125_SWI2C)
 	if (!swi2c_writeByte_A8(PAT9125_I2C_ADDR, addr, &data)) //NO ACK error
-	{
-		pat9125_PID1 = 0xff;
-		pat9125_PID2 = 0xff;
-		return;
-	}
-#endif //PAT9125_SWI2C
+        goto error;
+#elif defined(PAT9125_I2C)
+	if (twi_writeTo(PAT9125_I2C_ADDR,&addr,1,1,0) != 0 ||
+        twi_writeTo(PAT9125_I2C_ADDR,&data,1,1,1) != 0)
+        goto error;
+#endif
+    return;
+
+ error:
+    pat9125_PID1 = 0xff;
+    pat9125_PID2 = 0xff;
+    return;
 }
 
 uint8_t pat9125_wr_reg_verify(uint8_t addr, uint8_t data)

Firmware/twi.c

@@ -0,0 +1,561 @@
+/*
+  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_disable
+ * Desc     disables twi pins
+ * Input    none
+ * Output   none
+ */
+void twi_disable(void)
+{
+  // disable twi module, acks, and twi interrupt
+  TWCR &= ~(_BV(TWEN) | _BV(TWIE) | _BV(TWEA));
+
+  // deactivate internal pullups for twi.
+  digitalWrite(SDA, 0);
+  digitalWrite(SCL, 0);
+}
+
+/* 
+ * 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_setClock
+ * Desc     sets twi bit rate
+ * Input    Clock Frequency
+ * Output   none
+ */
+void twi_setFrequency(uint32_t frequency)
+{
+  TWBR = ((F_CPU / frequency) - 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 */
+}
+
+/* 
+ * 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 ourselves, and that would really confuse things.
+    twi_inRepStart = false;			// remember, we're dealing with an ASYNC ISR
+    do {
+      TWDR = twi_slarw;
+    } while(TWCR & _BV(TWWC));
+    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
+    do {
+      TWDR = twi_slarw;				
+    } while(TWCR & _BV(TWWC));
+    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 < (twi_txBufferLength+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
+  for(i = 0; i < length; ++i){
+    twi_txBuffer[twi_txBufferLength+i] = data[i];
+  }
+  twi_txBufferLength += length;
+  
+  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;
+}
+
+ISR(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
+      // ack future responses and leave slave receiver state
+      twi_releaseBus();
+      // 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);
+      // since we submit rx buffer to "wire" library, we can reset it
+      twi_rxBufferIndex = 0;
+      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;
+  }
+}
+

Firmware/twi.h

@@ -0,0 +1,55 @@
+/*
+  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 400000L
+  #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_disable(void);
+  void twi_setAddress(uint8_t);
+  void twi_setFrequency(uint32_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
+