twi.h File Reference

#include <inttypes.h>

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Defines
#define	CPU_FREQ   8000000L
#define	TWI_FREQ   100000L
#define	TWI_BUFFER_LENGTH   32
#define	TWI_READY   0
#define	TWI_MRX   1
#define	TWI_MTX   2
#define	TWI_SRX   3
#define	TWI_STX   4
Functions
void	twi_init (void)
void	twi_setAddress (uint8_t)
uint8_t	twi_readFrom (uint8_t, uint8_t *, uint8_t)
uint8_t	twi_writeTo (uint8_t, uint8_t *, uint8_t, uint8_t)
uint8_t	twi_transmit (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)
void	twi_close (void)

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Define Documentation

#define CPU_FREQ   8000000L

Definition at line 29 of file twi.h.

Referenced by twi_init().

#define TWI_BUFFER_LENGTH   32

Definition at line 37 of file twi.h.

Referenced by SIGNAL(), twi_init(), twi_readFrom(), twi_transmit(), and twi_writeTo().

#define TWI_FREQ   100000L

Definition at line 33 of file twi.h.

Referenced by twi_init().

#define TWI_MRX   1

Definition at line 41 of file twi.h.

Referenced by twi_readFrom().

#define TWI_MTX   2

Definition at line 42 of file twi.h.

Referenced by twi_writeTo().

#define TWI_READY   0

Definition at line 40 of file twi.h.

Referenced by SIGNAL(), twi_init(), twi_readFrom(), twi_releaseBus(), twi_stop(), and twi_writeTo().

#define TWI_SRX   3

Definition at line 43 of file twi.h.

Referenced by SIGNAL().

#define TWI_STX   4

Definition at line 44 of file twi.h.

Referenced by SIGNAL(), and twi_transmit().

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Function Documentation

void twi_attachSlaveRxEvent

(

void(*)(uint8_t *, int)

)

Definition at line 247 of file twi.c.

References twi_onSlaveReceive.

Referenced by TwoWire::begin().

{
  twi_onSlaveReceive = function;
}

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void twi_attachSlaveTxEvent

(

void(*)(void)

)

Definition at line 258 of file twi.c.

References twi_onSlaveTransmit.

Referenced by TwoWire::begin().

{
  twi_onSlaveTransmit = function;
}

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void twi_close

(

void

)

Definition at line 315 of file twi.c.

References cbi, sbi, twi_masterBuffer, twi_rxBuffer, and twi_txBuffer.

Referenced by TwoWire::close().

{       
        
        // de-activate internal pull-up resistors
        cbi(PORTD, 0);
        cbi(PORTD, 1);
        
        
        sbi(TWSR, TWPS0);
        sbi(TWSR, TWPS1);
        
  // disable twi module, acks, and twi interrupt
        sbi(TWCR,TWINT);
        sbi(TWCR,TWSTO);
        cbi(TWCR,TWEA);
        cbi(TWCR,TWSTA);
        cbi(TWCR,TWWC);
        sbi(TWCR,TWEN);
        cbi(TWCR,TWIE);
        cbi(PRR0,PRTWI);

        free(twi_masterBuffer);
        free(twi_txBuffer);
        free(twi_rxBuffer);
}

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void twi_init

(

void

)

Definition at line 62 of file twi.c.

References cbi, CPU_FREQ, sbi, TWI_BUFFER_LENGTH, TWI_FREQ, twi_masterBuffer, TWI_READY, twi_rxBuffer, twi_state, and twi_txBuffer.

Referenced by TwoWire::begin().

{
  // initialize state
  twi_state = TWI_READY;

  #if defined(__AVR_ATmega168__) || defined(__AVR_ATmega8__)
    // 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
    // this also applies to mega1281
    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; // FIXME!!

  /* 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));
}

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uint8_t twi_readFrom	(	uint8_t	,
		uint8_t *	,
		uint8_t
	)

Definition at line 120 of file twi.c.

References TWI_BUFFER_LENGTH, twi_masterBuffer, twi_masterBufferIndex, twi_masterBufferLength, TWI_MRX, TWI_READY, twi_slarw, and twi_state.

Referenced by TwoWire::requestFrom().

{
  uint8_t i;

  // ensure data will fit into buffer
  if(TWI_BUFFER_LENGTH < length){
    return 1;
  }

  // wait until twi is ready, become master receiver
  while(TWI_READY != twi_state){
    continue;
  }
  twi_state = TWI_MRX;

  // initialize buffer iteration vars
  twi_masterBufferIndex = 0;
  twi_masterBufferLength = length;

  // 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;
        }

  // copy twi buffer to data
  for(i = 0; i < length; ++i){
    data[i] = twi_masterBuffer[i];
  }
        
        return 0;
}

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void twi_releaseBus

(

void

)

Definition at line 306 of file twi.c.

References TWI_READY, and twi_state.

Referenced by SIGNAL().

{
  // release bus
  TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA) | _BV(TWINT);

  // update twi state
  twi_state = TWI_READY;
}

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void twi_reply

(

uint8_t

)

Definition at line 269 of file twi.c.

Referenced by SIGNAL().

{
        // 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);
  }
}

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void twi_setAddress

(

uint8_t

)

Definition at line 105 of file twi.c.

Referenced by TwoWire::begin().

{
  // set twi slave address (skip over TWGCE bit)
  TWAR = address << 1;
}

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void twi_stop

(

void

)

Definition at line 285 of file twi.c.

References TWI_READY, and twi_state.

Referenced by SIGNAL().

{
  // 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;
}

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uint8_t twi_transmit	(	uint8_t *	,
		uint8_t
	)

Definition at line 218 of file twi.c.

References TWI_BUFFER_LENGTH, twi_state, TWI_STX, twi_txBuffer, and twi_txBufferLength.

Referenced by TwoWire::send().

{
  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;
}

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uint8_t twi_writeTo	(	uint8_t	,
		uint8_t *	,
		uint8_t	,
		uint8_t
	)

Definition at line 169 of file twi.c.

References TWI_BUFFER_LENGTH, twi_masterBuffer, twi_masterBufferIndex, twi_masterBufferLength, TWI_MTX, TWI_READY, twi_slarw, and twi_state.

Referenced by TwoWire::endTransmission().

{
  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;

  // 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;
        }
        
        return 0;
}

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