/***************************************************************************
 *             __________               __   ___.
 *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
 *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
 *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
 *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
 *                     \/            \/     \/    \/            \/
 * $Id$
 *
 * Copyright (C) 2006 by Barry Wardell
 *
 * 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 "cpu.h"
#include "system.h"
#include "kernel.h"
#include "thread.h"
#include "adc.h"

static unsigned short adcdata[NUM_ADC_CHANNELS];

/* Scan ADC so that adcdata[channel] gets updated */
unsigned short adc_scan(int channel)
{
    unsigned int adc_data_1;
    unsigned int adc_data_2;

    /* Initialise */
    ADC_ADDR=0x130;
    ADC_STATUS=0;   /* 4 bytes, 1 per channel. Each byte is 0 if the channel is
                       off, 0x40 if the channel is on */
    
    /* Enable Channel */
    ADC_ADDR |= (0x1000000<<channel);
    
    /* Start? */
    ADC_ADDR |= 0x20000000;
    ADC_ADDR |= 0x80000000;
    
    /* ADC_DATA_1 and ADC_DATA_2 are both four bytes, one byte per channel.
       For each channel, ADC_DATA_1 stores the 8-bit msb, ADC_DATA_2 stores the
       2-bit lsb (in bits 0 and 1). Each channel is 10 bits total. */
    adc_data_1 = ((ADC_DATA_1 >> (8*channel)) & 0xff);
    adc_data_2 = ((ADC_DATA_2 >> (8*channel+6)) & 0x3);
    
    adcdata[channel] = (adc_data_1<<2 | adc_data_2);
    
    return adcdata[channel];
}

/* Read 10-bit channel data */
unsigned short adc_read(int channel)
{
    return adcdata[channel];
}

static int adc_counter;

static void adc_tick(void)
{
    if(++adc_counter == HZ)
    {
        adc_counter = 0;
        adc_scan(ADC_BATTERY);
        adc_scan(ADC_UNKNOWN_1);
        adc_scan(ADC_REMOTE);
        adc_scan(ADC_SCROLLPAD);
    }
}

void adc_init(void)
{
    /* Enable ADC */
    ADC_ENABLE_ADDR |= ADC_ENABLE;
    
    /* Initialise */
    ADC_INIT=0;

    /* Force a scan of all channels to get initial values */
    adc_scan(ADC_BATTERY);
    adc_scan(ADC_UNKNOWN_1);
    adc_scan(ADC_REMOTE);
    adc_scan(ADC_SCROLLPAD);
    
    /* FIXME: The ADC sometimes reads 0 for the battery
       voltage for the first few seconds. It would be better to fix this by
       figuring out how to use the ADC properly. Until then, work around the
       problem by waiting until it reads a proper value*/
    while(adc_scan(ADC_UNREG_POWER)==0);

    tick_add_task(adc_tick);
}