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