rockbox/firmware/drivers/adc.c

/***************************************************************************
 *             __________               __   ___.
 *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
 *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
 *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
 *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
 *                     \/            \/     \/    \/            \/
 * $Id$
 *
 * Copyright (C) 2002 by Linus Nielsen Feltzing
 *
 * All files in this archive are subject to the GNU General Public License.
 * See the file COPYING in the source tree root for full license agreement.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ****************************************************************************/
#include "config.h"
#include "sh7034.h"
#include "kernel.h"
#include "thread.h"
#include "adc.h"

static int current_channel;
static unsigned short adcdata[NUM_ADC_CHANNELS];
static unsigned int adcreg[NUM_ADC_CHANNELS] =
{
    ADDRAH_ADDR, ADDRBH_ADDR, ADDRCH_ADDR, ADDRDH_ADDR,
    ADDRAH_ADDR, ADDRBH_ADDR, ADDRCH_ADDR, ADDRDH_ADDR
};

static void adc_tick(void)
{
    /* Read the data that has bee converted since the last tick */
    adcdata[current_channel] =
	*(unsigned short *)adcreg[current_channel] >> 6;

    /* Start a conversion on the next channel */
    current_channel++;
    if(current_channel == NUM_ADC_CHANNELS)
        current_channel = 0;
    ADCSR = ADCSR_ADST | current_channel;
}

unsigned short adc_read(int channel)
{
    return adcdata[channel];
}

void adc_init(void)
{
    ADCR  = 0; /* No external trigger */
    
    current_channel = 0;
    tick_add_task(adc_tick);
}