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99 lines
2.0 KiB
C
99 lines
2.0 KiB
C
/*
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* Copyright (C) 2017 Freie Universität Berlin
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*
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* This file is subject to the terms and conditions of the GNU Lesser
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* General Public License v2.1. See the file LICENSE in the top level
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* directory for more details.
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*/
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/**
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* @ingroup cpu_sam3
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* @{
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*
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* @file
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* @brief Low-level ADC driver implementation
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*
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* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
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*
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* @}
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*/
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#include <assert.h>
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#include <stdio.h>
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#include "mutex.h"
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#include "periph/adc.h"
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#define RES_INVALID (0x0f)
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#define WP_KEY (0x414443)
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#define PMC_BIT (1 << (ID_ADC - 32))
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/* max ADC clock is 6.4MHz, we aim for 5MHz per default */
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#ifndef ADC_CLOCK_TARGET
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#define ADC_CLOCK_TARGET (5000000)
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#endif
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#define PRESCALER ((CLOCK_CORECLOCK / (2 * ADC_CLOCK_TARGET)) - 1)
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static mutex_t lock = MUTEX_INIT;
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static inline void use(void)
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{
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mutex_lock(&lock);
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PMC->PMC_PCER1 = PMC_BIT;
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}
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static inline void done(void)
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{
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PMC->PMC_PCDR1 = PMC_BIT;
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mutex_unlock(&lock);
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}
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int adc_init(adc_t line)
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{
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assert(line < ADC_NUMOF);
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use();
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/* disable ADC write protection */
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ADC->ADC_WPMR = ADC_WPMR_WPKEY(WP_KEY);
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ADC->ADC_CHDR = 0x0000ffff;
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/* if line 15 is used, enable the temperature sensor */
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if (line == 15) {
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ADC->ADC_ACR |= ADC_ACR_TSON;
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}
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done();
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return 0;
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}
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int32_t adc_sample(adc_t line, adc_res_t res)
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{
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assert(line < ADC_NUMOF);
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/* check if resolution is applicable */
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if (res & RES_INVALID) {
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return -1;
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}
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use();
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/* set resolution */
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ADC->ADC_MR = (res | ADC_MR_PRESCAL(PRESCALER));
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/* enable channel */
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ADC->ADC_CHER = (1 << line);
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/* start conversion */
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ADC->ADC_CR = ADC_CR_START;
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/* wait for result */
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while (!(ADC->ADC_ISR & ADC_ISR_DRDY)) {}
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/* read result */
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int sample = (int)(ADC->ADC_LCDR & ADC_LCDR_LDATA_Msk);
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/* disable channel */
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ADC->ADC_CHDR = (1 << line);
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done();
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return sample;
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}
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