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/***************************************************************************
* __________ __ ___.
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
* \/ \/ \/ \/ \/
* $Id$
*
* Copyright (C) 2006 by Wade Brown
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
****************************************************************************/
#include "cpu.h"
#include "system.h"
#include "adc.h"
#include "adc-target.h"
#include "kernel.h"
static unsigned short adc_readings[NUM_ADC_CHANNELS];
/* prototypes */
static unsigned short __adc_read(int channel);
static void adc_tick(void);
void adc_init(void)
{
int i;
/* Turn on the ADC PCLK */
s3c_regset32(&CLKCON, 1<<15);
/* Set channel 0, normal mode, disable "start by read" */
ADCCON &= ~(0x3F);
/* No start delay. Use normal conversion mode. */
ADCDLY = 0x1;
/* Set and enable the prescaler */
ADCCON = (ADCCON & ~(0xff<<6)) | (0x19<<6);
ADCCON |= (1<<14);
/* prefill the adc channels */
for (i = 0; i < NUM_ADC_CHANNELS; i++)
{
adc_readings[i] = __adc_read(i);
}
/* start at zero so when the tick starts it is at zero */
adc_readings[0] = __adc_read(0);
/* attach the adc reading to the tick */
tick_add_task(adc_tick);
}
/* Called to get the recent ADC reading */
inline unsigned short adc_read(int channel)
{
return adc_readings[channel];
}
/**
* Read the ADC by polling
* @param channel The ADC channel to read
* @return 10bit reading from ADC channel or ADC_READ_ERROR if timeout
*/
static unsigned short __adc_read(int channel)
{
int i;
/* Set the channel */
ADCCON = (ADCCON & ~(0x7<<3)) | (channel<<3);
/* Start the conversion process */
ADCCON |= 0x1;
/* Wait for a low Enable_start */
for (i = 20000;;)
{
if(0 == (ADCCON & 0x1))
{
break;
}
else
{
i--;
if (0 == i)
{
/* Ran out of time */
return ADC_READ_ERROR;
}
}
}
/* Wait for high End_of_Conversion */
for(i = 20000;;)
{
if(ADCCON & (1<<15))
{
break;
}
else
{
i--;
if(0 == i)
{
/* Ran out of time */
return ADC_READ_ERROR;
}
}
}
return (ADCDAT0 & 0x3ff);
}
/* add this to the tick so that the ADC converts are done in the background */
static void adc_tick(void)
{
static unsigned channel;
/* Check if the End Of Conversion is set */
if (ADCCON & (1<<15))
{
adc_readings[channel] = (ADCDAT0 & 0x3FF);
if (++channel >= NUM_ADC_CHANNELS)
{
channel = 0;
}
/* setup the next conversion and start it*/
ADCCON = (ADCCON & ~(0x7<<3)) | (channel<<3) | 0x01;
}
}
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