adc.c
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/*
* Copyright (C) 2014-2016 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.
*/
/**
* @ingroup cpu_stm32f4
* @{
*
* @file
* @brief Low-level ADC driver implementation
*
* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
*
* @}
*/
#include "cpu.h"
#include "mutex.h"
#include "periph/adc.h"
#include "periph_conf.h"
#ifdef ADC_CONFIG
/**
* @brief Maximum allowed ADC clock speed
*/
#define MAX_ADC_SPEED (12000000U)
/**
* @brief Load the ADC configuration
*/
static const adc_conf_t adc_config[] = ADC_CONFIG;
/**
* @brief Allocate locks for all three available ADC devices
*/
static mutex_t locks[] = {
#if ADC_DEVS > 1
MUTEX_INIT,
#endif
#if ADC_DEVS > 2
MUTEX_INIT,
#endif
MUTEX_INIT
};
static inline ADC_TypeDef *dev(adc_t line)
{
return (ADC_TypeDef *)(ADC1_BASE + (adc_config[line].dev << 8));
}
static inline void prep(adc_t line)
{
mutex_lock(&locks[adc_config[line].dev]);
periph_clk_en(APB2, (RCC_APB2ENR_ADC1EN << adc_config[line].dev));
}
static inline void done(adc_t line)
{
periph_clk_dis(APB2, (RCC_APB2ENR_ADC1EN << adc_config[line].dev));
mutex_unlock(&locks[adc_config[line].dev]);
}
int adc_init(adc_t line)
{
uint32_t clk_div = 2;
/* check if the line is valid */
if (line >= ADC_NUMOF) {
return -1;
}
/* lock and power-on the device */
prep(line);
/* configure the pin */
gpio_init_analog(adc_config[line].pin);
/* set sequence length to 1 conversion and enable the ADC device */
dev(line)->SQR1 = 0;
dev(line)->CR2 = ADC_CR2_ADON;
/* set clock prescaler to get the maximal possible ADC clock value */
for (clk_div = 2; clk_div < 8; clk_div += 2) {
if ((CLOCK_CORECLOCK / clk_div) <= MAX_ADC_SPEED) {
break;
}
}
ADC->CCR = ((clk_div / 2) - 1) << 16;
/* free the device again */
done(line);
return 0;
}
int adc_sample(adc_t line, adc_res_t res)
{
int sample;
/* check if resolution is applicable */
if (res < 0xff) {
return -1;
}
/* lock and power on the ADC device */
prep(line);
/* set resolution and conversion channel */
dev(line)->CR1 = res;
dev(line)->SQR3 = adc_config[line].chan;
/* start conversion and wait for results */
dev(line)->CR2 |= ADC_CR2_SWSTART;
while (!(dev(line)->SR & ADC_SR_EOC)) {}
/* finally read sample and reset the STRT bit in the status register */
sample = (int)dev(line)->DR;
/* power off and unlock device again */
done(line);
return sample;
}
#else
typedef int dont_be_pedantic;
#endif /* ADC_CONFIG */