source: trunk/FirmwareFX2/fx2/i2c.c@ 86

/* -*- c++ -*- */
/*-----------------------------------------------------------------------------
 * I2C read/write functions for FX2
 *-----------------------------------------------------------------------------
 * Code taken from USRP2 firmware (GNU Radio Project), version 3.0.2,
 * Copyright 2003 Free Software Foundation, Inc.
 *-----------------------------------------------------------------------------
 * This code is part of usbjtag. usbjtag 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. usbjtag 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 in the file
 * COPYING; if not, write to the Free Software Foundation, Inc., 51 Franklin
 * St, Fifth Floor, Boston, MA  02110-1301  USA
 *-----------------------------------------------------------------------------
 */

#include "i2c.h"
#include "fx2regs.h"
#include <string.h>


// issue a stop bus cycle and wait for completion


// returns non-zero if successful, else 0
unsigned char
i2c_read (unsigned char addr, xdata unsigned char *buf, unsigned char len)
{
  volatile unsigned char        junk;
  
  if (len == 0)                 // reading zero bytes always works
    return 1;
  
  while (I2CS & bmSTOP)         // wait for stop to clear
    ;

  I2CS = bmSTART;
  I2DAT = (addr << 1) | 1;      // write address and direction (1's the read bit)

  while ((I2CS & bmDONE) == 0)
    ;

  if ((I2CS & bmBERR) || (I2CS & bmACK) == 0)   // no device answered...
    goto fail;

  if (len == 1)
    I2CS |= bmLASTRD;           

  junk = I2DAT;                 // trigger the first read cycle

  while (--len != 0){
    while ((I2CS & bmDONE) == 0)
      ;

    if (I2CS & bmBERR)
      goto fail;

    if (len == 1)
      I2CS |= bmLASTRD;
    
    *buf++ = I2DAT;             // get data, trigger another read
  }

  // wait for final byte
  
  while ((I2CS & bmDONE) == 0)
    ;
  
  if (I2CS & bmBERR)
    goto fail;

  I2CS |= bmSTOP;
  *buf = I2DAT;

  return 1;

 fail:
  I2CS |= bmSTOP;
  return 0;
}



// returns non-zero if successful, else 0
unsigned char
i2c_write (unsigned char addr, xdata const unsigned char *buf, unsigned char len)
{
  while (I2CS & bmSTOP)         // wait for stop to clear
    ;

  I2CS = bmSTART;
  I2DAT = (addr << 1) | 0;      // write address and direction (0's the write bit)

  while ((I2CS & bmDONE) == 0)
    ;

  if ((I2CS & bmBERR) || (I2CS & bmACK) == 0)   // no device answered...
    goto fail;

  while (len > 0){
    I2DAT = *buf++;
    len--;

    while ((I2CS & bmDONE) == 0)
      ;

    if ((I2CS & bmBERR) || (I2CS & bmACK) == 0) // no device answered...
      goto fail;
  }

  I2CS |= bmSTOP;
  return 1;

 fail:
  I2CS |= bmSTOP;
  return 0;
}