firmware/target/arm/tcc77x/adc-tcc77x.c

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  * $Id$
   9  *
  10  * Copyright (C) 2007 by Dave Chapman
  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, 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 channel_group;
  51 static unsigned short adcdata[8];
  52
  53 /* Tick task */
  54 static void adc_tick(void)
  55 {
  56     /* Start a conversion of channels 0-3. This will trigger an interrupt,
  57        and the interrupt handler will take care of channels 4-7. */
  58
  59     int i;
  60
  61     PCLKCFG6 |= (1<<15);   /* Enable ADC clock */
  62
  63     channel_group = 0;
  64
  65     /* Start converting the first 4 channels */
  66     for (i = 0; i < 4; i++)
  67         ADCCON = i;
  68
  69 }
  70
  71 /* IRQ handler */
  72 void ADC(void)
  73 {
  74     int num;
  75     int i;
  76     uint32_t adc_status;
  77
  78     do
  79     {
  80         adc_status = ADCSTATUS;
  81         num = (adc_status>>24) & 7;
  82         if (num) adcdata[(adc_status >> 16) & 0x7] = adc_status & 0x3ff;
  83     } while (num);
  84
  85
  86     if (channel_group == 0)
  87     {
  88         /* Start conversion of channels 4-7 */
  89         for (i = 4; i < 8; i++)
  90             ADCCON = i;
  91
  92         channel_group = 1;
  93     }
  94     else
  95     {
  96         PCLKCFG6 &= ~(1<<15);   /* Disable ADC clock */
  97     }
  98 }
  99
 100 unsigned short adc_read(int channel)
 101 {
 102     return adcdata[channel];
 103 }
 104
 105 void adc_init(void)
 106 {
 107     /* Initialize ADC clocks */
 108     PCLKCFG6 = (PCLKCFG6 & 0xffff0000) | 4004;
 109
 110     ADCCON = (1<<4);         /* Leave standby mode */
 111
 112     /* IRQ enable, auto power-down, single-mode */
 113     ADCCFG |= (1<<3) | (1<<1) | (1<<0);
 114
 115     /* Unmask ADC IRQ */
 116     IEN |= ADC_IRQ_MASK;
 117
 118     tick_add_task(adc_tick);
 119
 120     sleep(2);   /* Ensure adc_data[] contains data before returning */
 121 }