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/***************************************************************************
* __________ __ ___.
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
* \/ \/ \/ \/ \/
* $Id$
*
* Copyright (C) 2002 by Linus Nielsen Feltzing
*
* 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 (approx. 256*4 cycles later), 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 current_channel;
static unsigned short adcdata[NUM_ADC_CHANNELS];
static void adc_tick(void)
{
/* Start a conversion of channel group 0. This will trigger an interrupt,
and the interrupt handler will take care of group 1. */
current_channel = 0;
ADCSR = ADCSR_ADST | ADCSR_ADIE | ADCSR_SCAN | 3;
}
void ADITI(void) __attribute__((interrupt_handler));
void ADITI(void)
{
if(ADCSR & ADCSR_ADF)
{
ADCSR = 0;
if(current_channel == 0)
{
adcdata[0] = ADDRA >> 6;
adcdata[1] = ADDRB >> 6;
adcdata[2] = ADDRC >> 6;
adcdata[3] = ADDRD >> 6;
current_channel = 4;
/* Convert the next group */
ADCSR = ADCSR_ADST | ADCSR_ADIE | ADCSR_SCAN | 7;
}
else
{
adcdata[4] = ADDRA >> 6;
adcdata[5] = ADDRB >> 6;
adcdata[6] = ADDRC >> 6;
adcdata[7] = ADDRD >> 6;
}
}
}
unsigned short adc_read(int channel)
{
return adcdata[channel];
}
void adc_init(void)
{
ADCR = 0x7f; /* No external trigger; other bits should be 1 according
to the manual... */
ADCSR = 0;
current_channel = 0;
/* Enable the A/D IRQ on level 1 */
IPRE = (IPRE & 0xf0ff) | 0x0100;
tick_add_task(adc_tick);
sleep(2); /* Ensure valid readings when adc_init returns */
}
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