qmk_firmware/keyboards/sx60/twimaster.c

/*************************************************************************
* Title:    I2C master library using hardware TWI interface
* Author:   Peter Fleury <pfleury@gmx.ch>  http://jump.to/fleury
* File:     $Id: twimaster.c,v 1.3 2005/07/02 11:14:21 Peter Exp $
* Software: AVR-GCC 3.4.3 / avr-libc 1.2.3
* Target:   any AVR device with hardware TWI
* Usage:    API compatible with I2C Software Library i2cmaster.h
**************************************************************************/
#include <inttypes.h>
#include <compat/twi.h>

#include <i2cmaster.h>

/* define CPU frequency in Hz here if not defined in Makefile */
#ifndef F_CPU
#define F_CPU 16000000UL
#endif

/* I2C clock in Hz */
#define SCL_CLOCK  400000L


/*************************************************************************
 Initialization of the I2C bus interface. Need to be called only once
*************************************************************************/
void i2c_init(void)
{
  /* initialize TWI clock
   * minimal values in Bit Rate Register (TWBR) and minimal Prescaler
   * bits in the TWI Status Register should give us maximal possible
   * I2C bus speed - about 444 kHz
   *
   * for more details, see 20.5.2 in ATmega16/32 secification
   */

  TWSR = 0;     /* no prescaler */
  TWBR = 10;    /* must be >= 10 for stable operation */

}/* i2c_init */


/*************************************************************************
  Issues a start condition and sends address and transfer direction.
  return 0 = device accessible, 1= failed to access device
*************************************************************************/
unsigned char i2c_start(unsigned char address)
{
    uint8_t   twst;

  /* send START condition */
  TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN);
 
  /* wait until transmission completed */
  while(!(TWCR & (1<<TWINT)));

  /* check value of TWI Status Register. Mask prescaler bits. */
  twst = TW_STATUS & 0xF8;
  if ( (twst != TW_START) && (twst != TW_REP_START)) return 1;

  /* send device address */
  TWDR = address;
  TWCR = (1<<TWINT) | (1<<TWEN);

  /* wail until transmission completed and ACK/NACK has been received */
  while(!(TWCR & (1<<TWINT)));

  /* check value of TWI Status Register. Mask prescaler bits. */
  twst = TW_STATUS & 0xF8;
  if ( (twst != TW_MT_SLA_ACK) && (twst != TW_MR_SLA_ACK) ) return 1;

  return 0;

}/* i2c_start */


/*************************************************************************
 Issues a start condition and sends address and transfer direction.
 If device is busy, use ack polling to wait until device is ready

 Input:   address and transfer direction of I2C device
*************************************************************************/
void i2c_start_wait(unsigned char address)
{
    uint8_t   twst;


    while ( 1 )
    {
      /* send START condition */
      TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN);

      /* wait until transmission completed */
      while(!(TWCR & (1<<TWINT)));

      /* check value of TWI Status Register. Mask prescaler bits. */
      twst = TW_STATUS & 0xF8;
      if ( (twst != TW_START) && (twst != TW_REP_START)) continue;

      /* send device address */
      TWDR = address;
      TWCR = (1<<TWINT) | (1<<TWEN);

      /* wail until transmission completed */
      while(!(TWCR & (1<<TWINT)));

      /* check value of TWI Status Register. Mask prescaler bits. */
      twst = TW_STATUS & 0xF8;
      if ( (twst == TW_MT_SLA_NACK )||(twst ==TW_MR_DATA_NACK) )
      {
          /* device busy, send stop condition to terminate write operation */
          TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);

          /* wait until stop condition is executed and bus released */
          while(TWCR & (1<<TWSTO));

          continue;
      }
      
      break;
     }

}/* i2c_start_wait */


/*************************************************************************
 Issues a repeated start condition and sends address and transfer direction

 Input:   address and transfer direction of I2C device

 Return:  0 device accessible
          1 failed to access device
*************************************************************************/
unsigned char i2c_rep_start(unsigned char address)
{
    return i2c_start( address );

}/* i2c_rep_start */


/*************************************************************************
 Terminates the data transfer and releases the I2C bus
*************************************************************************/
void i2c_stop(void)
{
  /* send stop condition */
  TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);

  /* wait until stop condition is executed and bus released */
  while(TWCR & (1<<TWSTO));

}/* i2c_stop */


/*************************************************************************
  Send one byte to I2C device

  Input:    byte to be transfered
  Return:   0 write successful
            1 write failed
*************************************************************************/
unsigned char i2c_write( unsigned char data )
{
    uint8_t   twst;

  /* send data to the previously addressed device */
  TWDR = data;
  TWCR = (1<<TWINT) | (1<<TWEN);

  /* wait until transmission completed */
  while(!(TWCR & (1<<TWINT)));

  /* check value of TWI Status Register. Mask prescaler bits */
  twst = TW_STATUS & 0xF8;
  if( twst != TW_MT_DATA_ACK) return 1;
  return 0;

}/* i2c_write */


/*************************************************************************
 Read one byte from the I2C device, request more data from device

 Return:  byte read from I2C device
*************************************************************************/
unsigned char i2c_readAck(void)
{
  TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWEA);
  while(!(TWCR & (1<<TWINT)));

  return TWDR;

}/* i2c_readAck */


/*************************************************************************
 Read one byte from the I2C device, read is followed by a stop condition

 Return:  byte read from I2C device
*************************************************************************/
unsigned char i2c_readNak(void)
{
  TWCR = (1<<TWINT) | (1<<TWEN);
  while(!(TWCR & (1<<TWINT)));

  return TWDR;

}/* i2c_readNak */