rockbox/firmware/target/coldfire/iriver/h100/adc-h100.c

/***************************************************************************
 *             __________               __   ___.
 *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
 *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
 *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
 *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
 *                     \/            \/     \/    \/            \/
 * $Id$
 *
 * Copyright (C) 2006 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 "cpu.h"
#include "system.h"
#include "kernel.h"
#include "thread.h"
#include "adc.h"
static unsigned char adcdata[NUM_ADC_CHANNELS];


#define CS_LO  and_l(~0x80, &GPIO_OUT)
#define CS_HI  or_l(0x80, &GPIO_OUT)
#define CLK_LO and_l(~0x00400000, &GPIO_OUT)
#define CLK_HI or_l(0x00400000, &GPIO_OUT)
#define DO     (GPIO_READ & 0x80000000)
#define DI_LO  and_l(~0x00200000, &GPIO_OUT)
#define DI_HI  or_l(0x00200000, &GPIO_OUT)

/* delay loop */
#define DELAY   do { int _x; for(_x=0;_x<10;_x++) asm volatile ("");} while (0)

unsigned short adc_scan(int channel)
{
    unsigned char data = 0;
    int i;
    
    CS_LO;

    DI_HI;  /* Start bit */
    DELAY;
    CLK_HI;
    DELAY;
    CLK_LO;
    
    DI_HI;  /* Single channel */
    DELAY;
    CLK_HI;
    DELAY;
    CLK_LO;

    if(channel & 1) /* LSB of channel number */
        DI_HI;
    else
        DI_LO;
    DELAY;
    CLK_HI;
    DELAY;
    CLK_LO;
    
    if(channel & 2) /* MSB of channel number */
        DI_HI;
    else
        DI_LO;
    DELAY;
    CLK_HI;
    DELAY;
    CLK_LO;

    DELAY;

    for(i = 0;i < 8;i++) /* 8 bits of data */
    {
        CLK_HI;
        DELAY;
        CLK_LO;
        DELAY;
        data <<= 1;
        data |= DO?1:0;
    }
    
    CS_HI;

    adcdata[channel] = data;

    return 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_REMOTEDETECT); /* Temporary. Remove when the remote
                                       detection feels stable. */
    }
}

void adc_init(void)
{
    or_l(0x80600080, &GPIO_FUNCTION); /* GPIO7:  CS
                                         GPIO21: Data In (to the ADC)
                                         GPIO22: CLK
                                         GPIO31: Data Out (from the ADC) */
    or_l(0x00600080, &GPIO_ENABLE);
    or_l(0x80, &GPIO_OUT);          /* CS high */
    and_l(~0x00400000, &GPIO_OUT);  /* CLK low */

    adc_scan(ADC_BATTERY);
    
    tick_add_task(adc_tick);
}