i2c.c

/*

  Copyright (C) 2000 Jesper Hansen <jesperh@telia.com>.

  This file is part of the yampp system.

  This program is free software; you can redistribute it and/or

  modify it under the terms of the GNU General Public License

  as published by the Free Software Foundation; either version 2

  of the License, or (at your option) any later version.

  This program 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 General Public License for more details.

  You should have received a copy of the GNU General Public License

  along with this program; if not, write to the Free Software Foundation, 

  Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

*/

#include <io.h>

#include <signal.h>

#include <progmem.h>

#define READ    0x01    // I2C READ bit

#define SCLPORT  PORTD

#define SDAPORT  PORTD

#define SCL  PB7

#define  SDA  PB5

#define QDEL  delay(5)

#define HDEL  delay(10)

#define I2C_SDL_LO      cbi( SDAPORT, SDA)

#define I2C_SDL_HI      sbi( SDAPORT, SDA)

#define I2C_SCL_LO      cbi( SCLPORT, SCL); 

#define I2C_SCL_HI      sbi( SCLPORT, SCL); 

//#define I2C_SCL_TOGGLE  HDEL; I2C_SCL_HI; HDEL; I2C_SCL_LO;

//#define I2C_START       I2C_SDL_LO; QDEL; I2C_SCL_LO; 

//#define I2C_STOP        HDEL; I2C_SCL_HI; QDEL; I2C_SDL_HI; HDEL;

//#define DEBUG_I2C  1

#define I2CTRACE(x)          PRINT(x) \

#define I2CTRACE2(a,b,c)  PRINT(a); UART_Printfu08(b); PRINT(c); \

void delay(unsigned short us) 

{

    unsigned short  delay_loops;

    register unsigned short  i;

    delay_loops = (us+3)/5*CYCLES_PER_US; // +3 for rounding up (dirty) 

  // one loop takes 5 cpu cycles 

    for (i=0; i < delay_loops; i++) {};

} 

void i2ct(void)

{

  HDEL; I2C_SCL_HI; HDEL; I2C_SCL_LO;

}

void i2cstart(void)

{

  I2C_SDL_LO; QDEL; I2C_SCL_LO; 

}

void i2cstop(void)

{

  HDEL; I2C_SCL_HI; QDEL; I2C_SDL_HI; HDEL;

}

#define I2C_SCL_TOGGLE  i2ct();

#define I2C_START       i2cstart();

#define I2C_STOP        i2cstop();  

//int q; // for debug

unsigned int i2c_putbyte(unsigned char b)

{

    int i;

#ifdef DEBUG_I2C

    I2CTRACE2("<",b,">");

#endif  

  for (i=7;i>=0;i--)

  {

    if ( b & (1<<i) )

          I2C_SDL_HI;

        else

            I2C_SDL_LO;   // address bit

        I2C_SCL_TOGGLE;     // clock HI, delay, then LO

    }

    I2C_SDL_HI;            // leave SDL HI

   // added    

  cbi(SDAPORT-1, SDA);  // change direction to input on SDA line (may not be needed)

  HDEL;

    I2C_SCL_HI;                     // clock back up

    b = inp(SDAPORT-2) & (1<<SDA);  // get the ACK bit

  HDEL;

    I2C_SCL_LO;  // not really ??

  sbi(SDAPORT-1, SDA);  // change direction back to output

  HDEL;

    return (b == 0);            // return ACK value

}

unsigned char i2c_getbyte(unsigned int last)

{

    int i;

    unsigned char c,b = 0;

    I2C_SDL_HI;            // make sure pullups are ativated

  cbi(SDAPORT-1, SDA);  // change direction to input on SDA line (may not be needed)

    for (i=7;i>=0;i--)

  {

    HDEL;

        I2C_SCL_HI;             // clock HI

      c = inp(SDAPORT-2) & (1<<SDA);  

        b <<= 1;

        if (c)

            b |= 1;

    HDEL;

      I2C_SCL_LO;             // clock LO

    }

  sbi(SDAPORT-1, SDA);  // change direction to output on SDA line

    if (last)

      I2C_SDL_HI;                  // set NAK

    else

      I2C_SDL_LO;                  // set ACK

    I2C_SCL_TOGGLE;            // clock pulse

    I2C_SDL_HI;            // leave with SDL HI

#ifdef DEBUG_I2C

    I2CTRACE2("<",b,">");

#endif  

    return b;            // return received byte

}

/**************************************************************************/

/* I2C public functions                           */

/**************************************************************************/

/*

    Initialize I2C communication

*/

void i2c_init(void)

{

  sbi( SDAPORT-1, SDA);  // set SDA as output

  sbi( SCLPORT-1, SCL);  // set SCL as output

  I2C_SDL_HI;

  I2C_SCL_HI;

}

/*

    Send a byte sequence on the I2C line

*/

void i2c_send(unsigned char dev, unsigned char sub, unsigned char length, unsigned char *data)

{

#ifdef DEBUG_I2C

    I2CTRACE("i2c_send ");

#endif  

    I2C_START;          // do start transition

    i2c_putbyte(dev);     // send DEVICE address

    i2c_putbyte(sub);     // and the subaddress

    // send the data

    while (length--)

        i2c_putbyte(*data++);

    I2C_SDL_LO;             // clear data line and

  I2C_STOP;               // send STOP transition

#ifdef DEBUG_I2C

    I2CTRACE("\n");

#endif  

}

/*

    Retrieve a byte sequence on the I2C line

*/

void i2c_receive(unsigned char dev, unsigned char sub, unsigned char length, unsigned char *data)

{

    int j = length;

    unsigned char *p = data;

#ifdef DEBUG_I2C

    I2CTRACE("i2c_receive ");

#endif  

    I2C_START;        // do start transition

    i2c_putbyte(dev);     // send DEVICE address

    i2c_putbyte(sub /*| READ*/);     // and the subaddress

  HDEL;

    I2C_SCL_HI;          // do a repeated START

    I2C_START;            // transition

    i2c_putbyte(dev | READ);// resend DEVICE, with READ bit set

    // receive data bytes

    while (j--)

        *p++ = i2c_getbyte(j == 0);

    I2C_SDL_LO;             // clear data line and

    I2C_STOP;               // send STOP transition

#ifdef DEBUG_I2C

    I2CTRACE("\n");

#endif  

}