firmware/target/arm/adc-as3514.c

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  * $Id$
   9  *
  10  * Copyright (C) 2006 by Barry Wardell
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License
  14  * as published by the Free Software Foundation; either version 2
  15  * of the License, or (at your option) any later version.
  16  *
  17  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  18  * KIND, either express or implied.
  19  *
  20  ****************************************************************************/
  21 #include "adc.h"
  22 #include "kernel.h"
  23 #include "ascodec.h"
  24 #include "as3514.h"
  25
  26 /* Read 10-bit channel data */
  27 unsigned short adc_read(int channel)
  28 {
  29     unsigned short data = 0;
  30
  31     if ((unsigned)channel >= NUM_ADC_CHANNELS)
  32         return 0;
  33
  34     ascodec_lock();
  35
  36     /* Select channel */
  37     if (ascodec_write(AS3514_ADC_0, (channel << 4)) >= 0)
  38     {
  39         unsigned char buf[2];
  40
  41         /*
  42          * The AS3514 ADC will trigger an interrupt when the conversion
  43          * is finished, if the corresponding enable bit in IRQ_ENRD2
  44          * is set.
  45          * Previously the code did not wait and this apparently did
  46          * not pose any problems, but this should be more correct.
  47          * Without the wait the data read back may be completely or
  48          * partially (first one of the two bytes) stale.
  49          */
  50         ascodec_wait_adc_finished();
  51
  52
  53         /* Read data */
  54         if (ascodec_readbytes(AS3514_ADC_0, 2, buf) >= 0)
  55         {
  56             data = (((buf[0] & 0x3) << 8) | buf[1]);
  57         }
  58     }
  59
  60     ascodec_unlock();
  61
  62     return data;
  63 }
  64
  65 void adc_init(void)
  66 {
  67 }