295367686e
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@11850 a1c6a512-1295-4272-9138-f99709370657
144 lines
3.1 KiB
C
144 lines
3.1 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) 2006 by Wade Brown
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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 "cpu.h"
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#include "adc-target.h"
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#include "kernel.h"
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static unsigned short adc_readings[NUM_ADC_CHANNELS];
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/* prototypes */
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static unsigned short __adc_read(int channel);
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static void adc_tick(void);
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void adc_init(void)
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{
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int i;
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/* Turn on the ADC PCLK */
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CLKCON |= (1<<15);
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/* Set channel 0, normal mode, disable "start by read" */
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ADCCON &= ~(0x3F);
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/* No start delay. Use normal conversion mode. */
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ADCDLY = 0x1;
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/* Set and enable the prescaler */
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ADCCON = (ADCCON & ~(0xff<<6)) | (0x19<<6);
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ADCCON |= (1<<14);
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/* prefill the adc channels */
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for (i = 0; i < NUM_ADC_CHANNELS; i++)
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{
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adc_readings[i] = __adc_read(i);
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}
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/* start at zero so when the tick starts it is at zero */
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adc_readings[0] = __adc_read(0);
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/* attach the adc reading to the tick */
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tick_add_task(adc_tick);
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}
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/* Called to get the recent ADC reading */
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inline unsigned short adc_read(int channel)
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{
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return adc_readings[channel];
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}
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/**
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* Read the ADC by polling
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* @param channel The ADC channel to read
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* @return 10bit reading from ADC channel or ADC_READ_ERROR if timeout
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*/
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static unsigned short __adc_read(int channel)
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{
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int i;
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/* Set the channel */
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ADCCON = (ADCCON & ~(0x7<<3)) | (channel<<3);
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/* Start the conversion process */
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ADCCON |= 0x1;
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/* Wait for a low Enable_start */
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for (i = 20000;;) {
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if(0 == (ADCCON & 0x1)) {
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break;
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}
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else {
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i--;
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if (0 == i) {
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/* Ran out of time */
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return ADC_READ_ERROR;
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}
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}
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}
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/* Wait for high End_of_Conversion */
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for(i = 20000;;) {
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if(ADCCON & (1<<15)) {
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break;
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}
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else {
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i--;
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if(0 == i) {
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/* Ran out of time */
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return ADC_READ_ERROR;
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}
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}
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}
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return (ADCDAT0 & 0x3ff);
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}
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/* add this to the tick so that the ADC converts are done in the background */
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static void adc_tick(void)
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{
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static unsigned channel;
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/* Check if the End Of Conversion is set */
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if (ADCCON & (1<<15))
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{
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adc_readings[channel] = (ADCDAT0 & 0x3FF);
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if (++channel >= NUM_ADC_CHANNELS)
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{
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channel = 0;
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}
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/* setup the next conversion and start it*/
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ADCCON = (ADCCON & ~(0x7<<3)) | (channel<<3) | 0x01;
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}
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}
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