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/***************************************************************************
* __________ __ ___.
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
* \/ \/ \/ \/ \/
* $Id$
*
* Copyright (C) 2007 by Dave Chapman
*
* 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 "config.h"
#include "cpu.h"
#include "system.h"
#include "kernel.h"
#include "thread.h"
#include "string.h"
#include "adc.h"
/**************************************************************************
** The A/D conversion is done every tick, in three steps:
**
** 1) On the tick interrupt, the conversion of channels 0-3 is started, and
** the A/D interrupt is enabled.
**
** 2) After the conversion is done, an interrupt
** is generated at level 1, which is the same level as the tick interrupt
** itself. This interrupt will be pending until the tick interrupt is
** finished.
** When the A/D interrupt is finally served, it will read the results
** from the first conversion and start the conversion of channels 4-7.
**
** 3) When the conversion of channels 4-7 is finished, the interrupt is
** triggered again, and the results are read. This time, no new
** conversion is started, it will be done in the next tick interrupt.
**
** Thus, each channel will be updated HZ times per second.
**
*************************************************************************/
static int channel_group;
static unsigned short adcdata[8];
/* Tick task */
static void adc_tick(void)
{
/* Start a conversion of channels 0-3. This will trigger an interrupt,
and the interrupt handler will take care of channels 4-7. */
int i;
PCLKCFG6 |= (1<<15); /* Enable ADC clock */
channel_group = 0;
/* Start converting the first 4 channels */
for (i = 0; i < 4; i++)
ADCCON = i;
}
/* IRQ handler */
void ADC(void)
{
int num;
int i;
uint32_t adc_status;
do
{
adc_status = ADCSTATUS;
num = (adc_status>>24) & 7;
if (num) adcdata[(adc_status >> 16) & 0x7] = adc_status & 0x3ff;
} while (num);
if (channel_group == 0)
{
/* Start conversion of channels 4-7 */
for (i = 4; i < 8; i++)
ADCCON = i;
channel_group = 1;
}
else
{
PCLKCFG6 &= ~(1<<15); /* Disable ADC clock */
}
}
unsigned short adc_read(int channel)
{
return adcdata[channel];
}
void adc_init(void)
{
/* Initialize ADC clocks */
PCLKCFG6 = (PCLKCFG6 & 0xffff0000) | 4004;
ADCCON = (1<<4); /* Leave standby mode */
/* IRQ enable, auto power-down, single-mode */
ADCCFG |= (1<<3) | (1<<1) | (1<<0);
/* Unmask ADC IRQ */
IEN |= ADC_IRQ_MASK;
tick_add_task(adc_tick);
sleep(2); /* Ensure adc_data[] contains data before returning */
}
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