adc.c
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/*
* Copyright (C) 2014-2016 Freie Universität Berlin
* 2015 Ludwig Knüpfer
*
* 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.
*/
/**
* @ingroup cpu_nrf51822
* @{
*
* @file
* @brief Low-level ADC driver implementation
*
* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
* @author Ludwig Knüpfer <ludwig.knuepfer@fu-berlin.de>
*
* @}
*/
#include "cpu.h"
#include "mutex.h"
#include "periph/adc.h"
#include "periph_conf.h"
#ifdef ADC_CONFIG
/**
* @brief Load the ADC configuration
*/
static const uint8_t adc_config[] = ADC_CONFIG;
/**
* @brief Lock to prevent concurrency issues when used from different threads
*/
static mutex_t lock;
static inline void prep(void)
{
mutex_lock(&lock);
NRF_ADC->POWER = 1;
NRF_ADC->ENABLE = 1;
}
static inline void done(void)
{
NRF_ADC->ENABLE = 0;
NRF_ADC->POWER = 0;
mutex_unlock(&lock);
}
int adc_init(adc_t line)
{
if (line >= ADC_NUMOF) {
return -1;
}
return 0;
}
int adc_sample(adc_t line, adc_res_t res)
{
int val;
/* check if resolution is valid */
if (res > 2) {
return -1;
}
/* prepare device */
prep();
/* set resolution, line, and use 1/3 input and ref voltage scaling */
NRF_ADC->CONFIG = ((ADC_CONFIG_REFSEL_SupplyOneThirdPrescaling << 5) |
(ADC_CONFIG_INPSEL_AnalogInputOneThirdPrescaling << 2) |
(1 << (adc_config[line] + 8)) |
res);
/* start conversion */
NRF_ADC->TASKS_START = 1;
/* wait for conversion to be complete */
while (NRF_ADC->BUSY == 1) {}
/* get result */
val = (int)NRF_ADC->RESULT;
/* free device */
done();
return val;
}
#else
typedef int dont_be_pedantic;
#endif /* ADC_CONFIG */