firmware/target/sh/adc-sh.c

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  * $Id$
   9  *
  10  * Copyright (C) 2002 by Linus Nielsen Feltzing
  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 "config.h"
  22 #include "cpu.h"
  23 #include "system.h"
  24 #include "kernel.h"
  25 #include "thread.h"
  26 #include "string.h"
  27 #include "adc.h"
  28
  29 /**************************************************************************
  30  ** The A/D conversion is done every tick, in three steps:
  31  **
  32  ** 1) On the tick interrupt, the conversion of channels 0-3 is started, and
  33  **    the A/D interrupt is enabled.
  34  **
  35  ** 2) After the conversion is done (approx. 256*4 cycles later), an interrupt
  36  **    is generated at level 1, which is the same level as the tick interrupt
  37  **    itself. This interrupt will be pending until the tick interrupt is
  38  **    finished.
  39  **    When the A/D interrupt is finally served, it will read the results
  40  **    from the first conversion and start the conversion of channels 4-7.
  41  **
  42  ** 3) When the conversion of channels 4-7 is finished, the interrupt is
  43  **    triggered again, and the results are read. This time, no new
  44  **    conversion is started, it will be done in the next tick interrupt.
  45  **
  46  ** Thus, each channel will be updated HZ times per second.
  47  **
  48  *************************************************************************/
  49
  50 static int current_channel;
  51 static unsigned short adcdata[NUM_ADC_CHANNELS];
  52
  53 static void adc_tick(void)
  54 {
  55     /* Start a conversion of channel group 0. This will trigger an interrupt,
  56        and the interrupt handler will take care of group 1. */
  57
  58     current_channel = 0;
  59     ADCSR = ADCSR_ADST | ADCSR_ADIE | ADCSR_SCAN | 3;
  60 }
  61
  62 void ADITI(void) __attribute__((interrupt_handler));
  63 void ADITI(void)
  64 {
  65     if(ADCSR & ADCSR_ADF)
  66     {
  67         ADCSR = 0;
  68
  69         if(current_channel == 0)
  70         {
  71             adcdata[0] = ADDRA >> 6;
  72             adcdata[1] = ADDRB >> 6;
  73             adcdata[2] = ADDRC >> 6;
  74             adcdata[3] = ADDRD >> 6;
  75             current_channel = 4;
  76
  77             /* Convert the next group */
  78             ADCSR = ADCSR_ADST | ADCSR_ADIE | ADCSR_SCAN | 7;
  79         }
  80         else
  81         {
  82             adcdata[4] = ADDRA >> 6;
  83             adcdata[5] = ADDRB >> 6;
  84             adcdata[6] = ADDRC >> 6;
  85             adcdata[7] = ADDRD >> 6;
  86         }
  87     }
  88 }
  89
  90 unsigned short adc_read(int channel)
  91 {
  92     return adcdata[channel];
  93 }
  94
  95 void adc_init(void)
  96 {
  97     ADCR  = 0x7f; /* No external trigger; other bits should be 1 according
  98                      to the manual... */
  99
 100     ADCSR = 0;
 101
 102     current_channel = 0;
 103
 104     /* Enable the A/D IRQ on level 1 */
 105     IPRE = (IPRE & 0xf0ff) | 0x0100;
 106
 107     tick_add_task(adc_tick);
 108
 109     sleep(2);    /* Ensure valid readings when adc_init returns */
 110 }