9c1ab1f057
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@17311 a1c6a512-1295-4272-9138-f99709370657
116 lines
3.3 KiB
C
116 lines
3.3 KiB
C
/***************************************************************************
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* __________ __ ___.
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* Open \______ \ ____ ____ | | _\_ |__ _______ ___
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* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
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* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
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* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
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* \/ \/ \/ \/ \/
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* $Id$
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*
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* Copyright (C) 2007 by Dave Chapman
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*
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* All files in this archive are subject to the GNU General Public License.
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* See the file COPYING in the source tree root for full license agreement.
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*
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* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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* KIND, either express or implied.
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*
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****************************************************************************/
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#include "config.h"
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#include "cpu.h"
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#include "system.h"
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#include "kernel.h"
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#include "thread.h"
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#include "string.h"
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#include "adc.h"
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/**************************************************************************
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** The A/D conversion is done every tick, in three steps:
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**
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** 1) On the tick interrupt, the conversion of channels 0-3 is started, and
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** the A/D interrupt is enabled.
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**
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** 2) After the conversion is done, an interrupt
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** is generated at level 1, which is the same level as the tick interrupt
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** itself. This interrupt will be pending until the tick interrupt is
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** finished.
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** When the A/D interrupt is finally served, it will read the results
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** from the first conversion and start the conversion of channels 4-7.
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**
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** 3) When the conversion of channels 4-7 is finished, the interrupt is
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** triggered again, and the results are read. This time, no new
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** conversion is started, it will be done in the next tick interrupt.
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**
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** Thus, each channel will be updated HZ times per second.
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**
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*************************************************************************/
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static int channel_group;
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static unsigned short adcdata[8];
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/* Tick task */
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static void adc_tick(void)
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{
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/* Start a conversion of channels 0-3. This will trigger an interrupt,
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and the interrupt handler will take care of channels 4-7. */
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int i;
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PCLKCFG6 |= (1<<15); /* Enable ADC clock */
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channel_group = 0;
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/* Start converting the first 4 channels */
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for (i = 0; i < 4; i++)
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ADCCON = i;
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}
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/* IRQ handler */
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void ADC(void)
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{
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int num;
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int i;
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uint32_t adc_status;
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do
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{
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adc_status = ADCSTATUS;
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num = (adc_status>>24) & 7;
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if (num) adcdata[(adc_status >> 16) & 0x7] = adc_status & 0x3ff;
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} while (num);
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if (channel_group == 0)
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{
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/* Start conversion of channels 4-7 */
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for (i = 4; i < 8; i++)
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ADCCON = i;
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channel_group = 1;
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}
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else
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{
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PCLKCFG6 &= ~(1<<15); /* Disable ADC clock */
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}
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}
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unsigned short adc_read(int channel)
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{
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return adcdata[channel];
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}
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void adc_init(void)
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{
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ADCCON = (1<<4); /* Leave standby mode */
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/* IRQ enable, auto power-down, single-mode */
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ADCCFG |= (1<<3) | (1<<1) | (1<<0);
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/* Unmask ADC IRQ */
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IEN |= ADC_IRQ_MASK;
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tick_add_task(adc_tick);
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sleep(2); /* Ensure adc_data[] contains data before returning */
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}
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