cpu/stm32l1: add adc support

cpu/stm32l1/include/periph_cpu.h

@@ -49,6 +49,30 @@ typedef struct {
     uint8_t chan;           /**< DAC device used for this line */
 } dac_conf_t;
 
+
+/**
+ * @brief   ADC channel configuration data
+ */
+typedef struct {
+    gpio_t pin;             /**< pin connected to the channel */
+    uint8_t chan;           /**< CPU ADC channel connected to the pin */
+} adc_conf_t;
+
+/**
+ * @brief   Override the ADC resolution configuration
+ * @{
+ */
+#define HAVE_ADC_RES_T
+typedef enum {
+    ADC_RES_6BIT  = (0x3 << 3),  /**< ADC resolution: 6 bit */
+    ADC_RES_8BIT  = (0x2 << 3),  /**< ADC resolution: 8 bit */
+    ADC_RES_10BIT = (0x1 << 3),  /**< ADC resolution: 10 bit */
+    ADC_RES_12BIT = (0x0 << 3),  /**< ADC resolution: 12 bit */
+    ADC_RES_14BIT = (0xfe),      /**< not applicable */
+    ADC_RES_16BIT = (0xff)       /**< not applicable */
+} adc_res_t;
+/** @} */
+
 /**
  * @brief   I2C configuration data structure
  */

cpu/stm32l1/periph/adc.c

@@ -0,0 +1,137 @@
+/*
+ * Copyright (C) 2016 Fundacion Inria Chile
+ *
+ * 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_stm32l1
+ * @{
+ *
+ * @file
+ * @brief       Low-level ADC driver implementation
+ *
+ * @author      Francisco Molina <francisco.molina@inria.cl>
+ * @author      Hauke Petersen <hauke.petersen@fu-berlin.de>
+ * @author      Nick v. IJzendoorn <nijzendoorn@engineering-spirit.nl>
+ *
+ * @}
+ */
+
+#include "cpu.h"
+#include "mutex.h"
+#include "periph/adc.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 device
+ *
+ * All STM32l1 CPU's have single ADC device
+ */
+static mutex_t lock = MUTEX_INIT;
+
+static inline void prep(void)
+{
+    mutex_lock(&lock);
+    RCC->APB2ENR |= RCC_APB2ENR_ADC1EN;
+}
+
+static inline void done(void)
+{
+    RCC->APB2ENR &= ~(RCC_APB2ENR_ADC1EN);
+    mutex_unlock(&lock);
+}
+
+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();
+
+    /* configure the pin */
+    if ((adc_config[line].pin != GPIO_UNDEF))
+        gpio_init_analog(adc_config[line].pin);
+
+    /* 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;
+
+    /* check if this channel is an internal ADC channel, if so
+     * enable the internal temperature and Vref */
+    if (adc_config[line].chan == 16 || adc_config[line].chan == 17) {
+        ADC->CCR |= ADC_CCR_TSVREFE;
+    }
+
+    /* enable the ADC module */
+    ADC1->CR2 = ADC_CR2_ADON;
+    /* turn off during idle phase*/
+    ADC1->CR1 = ADC_CR1_PDI;
+
+    /* free the device again */
+    done();
+
+    return 0;
+}
+
+int adc_sample(adc_t line, adc_res_t res)
+{
+    int sample;
+
+    /* check if resolution is applicable */
+    if ( (res != ADC_RES_6BIT) &&
+         (res != ADC_RES_8BIT) &&
+         (res != ADC_RES_10BIT) &&
+         (res != ADC_RES_12BIT)) {
+        return -1;
+    }
+
+    /* lock and power on the ADC device  */
+    prep();
+
+    /* set resolution, conversion channel and single read */
+    ADC1->CR1 |= res & ADC_CR1_RES;
+    ADC1->SQR1 &= ~ADC_SQR1_L;
+    ADC1->SQR5 = adc_config[line].chan;
+
+    /* wait for regulat channel to be ready*/
+    while (!(ADC1->SR & ADC_SR_RCNR)) {}
+    /* start conversion and wait for results */
+    ADC1->CR2 |= ADC_CR2_SWSTART;
+    while (!(ADC1->SR & ADC_SR_EOC)) {}
+    /* finally read sample and reset the STRT bit in the status register */
+    sample = (int)ADC1->DR;
+    ADC1 -> SR &= ~ADC_SR_STRT;
+
+    /* power off and unlock device again */
+    done();
+
+    return sample;
+}
+
+#else
+typedef int dont_be_pedantic;
+#endif /* ADC_CONFIG */