cpu/stm32l4: add adc support

boards/nucleo-l476rg/Makefile.features

 # Put defined MCU peripherals here (in alphabetical order)
+FEATURES_PROVIDED += periph_adc
 FEATURES_PROVIDED += periph_gpio
 FEATURES_PROVIDED += periph_pwm
 FEATURES_PROVIDED += periph_rtc

boards/nucleo-l476rg/include/periph_conf.h

@@ -245,9 +245,20 @@ static const spi_conf_t spi_config[] = {
 
 /**
  * @name    ADC configuration
+ *
+ * configure only  ADC channels for the Arduino header pins A0-A5
+ *
  * @{
  */
-#define ADC_NUMOF           (0)
+#define ADC_NUMOF           (6U)
+#define ADC_CONFIG {             \
+    {GPIO_PIN(PORT_A, 0), 0, 5},  /*< ADC12_IN5 */   \
+    {GPIO_PIN(PORT_A, 1), 0, 6},  /*< ADC12_IN6 */   \
+    {GPIO_PIN(PORT_A, 4), 1, 9},  /*< ADC12_IN9 */   \
+    {GPIO_PIN(PORT_B, 0), 1, 15}, /*< ADC12_IN15 */  \
+    {GPIO_PIN(PORT_C, 1), 2, 2},  /*< ADC123_IN_2 */ \
+    {GPIO_PIN(PORT_C, 0), 2, 1},  /*< ADC123_IN_1 */ \
+}
 /** @} */
 
 /**

cpu/stm32l4/include/periph_cpu.h

@@ -45,6 +45,23 @@ enum {
     PORT_H = 7,             /**< port H */
 };
 
+/**
+ * @brief   Available number of ADC devices
+ */
+#if defined(CPU_MODEL_STM32L476RG) || defined(CPU_MODEL_STM32L475VG)
+#define ADC_DEVS            (3U)
+#elif defined(CPU_MODEL_STM32L452RE) || defined(CPU_MODEL_STM32L432KC)
+#define ADC_DEVS            (1U)
+#endif
+
+#if defined(CPU_MODEL_STM32L476RG) || defined(CPU_MODEL_STM32L475VG) || \
+    defined(CPU_MODEL_STM32L452RE) || defined(CPU_MODEL_STM32L432KC)
+/**
+ * @brief   ADC voltage regulator start-up time [us]
+ */
+#define ADC_T_ADCVREG_STUP_US (20)
+#endif
+
 #ifndef DOXYGEN
 /**
  * @brief   Override ADC resolution values
@@ -52,22 +69,23 @@ enum {
  */
 #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_6BIT  = (ADC_CFGR_RES),   /**< ADC resolution: 6 bit */
+    ADC_RES_8BIT  = (ADC_CFGR_RES_1), /**< ADC resolution: 8 bit */
+    ADC_RES_10BIT = (ADC_CFGR_RES_0), /**< ADC resolution: 10 bit */
+    ADC_RES_12BIT = (0x0),            /**< ADC resolution: 12 bit */
+    ADC_RES_14BIT = (0x1),            /**< not applicable */
+    ADC_RES_16BIT = (0x2)             /**< not applicable */
 } adc_res_t;
 /** @} */
 #endif /* ndef DOXYGEN */
 
 /**
- * @brief   ADC line configuration values
+ * @brief   ADC channel configuration data
  */
 typedef struct {
-    gpio_t pin;             /**< pin to use */
-    uint8_t chan;           /**< internal channel the pin is connected to */
+    gpio_t pin;             /**< pin connected to the channel */
+    uint8_t dev;            /**< ADCx - 1 device used for the channel */
+    uint8_t chan;           /**< CPU ADC channel connected to the pin */
 } adc_conf_t;
 
 #ifdef __cplusplus

cpu/stm32l4/periph/adc.c

+/*
+ * Copyright (C) 2014-2016 Freie Universität Berlin
+ * Copyright (C) 2018 HAW-Hamburg
+ *
+ * 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_stm32l4
+ * @ingroup     drivers_periph_adc
+ * @{
+ *
+ * @file
+ * @brief       Low-level ADC driver implementation
+ *
+ * @author      Hauke Petersen <hauke.petersen@fu-berlin.de>
+ * @author      Michel Rottleuthner <michel.rottleuthner@haw-hamburg.de>
+ *
+ * @}
+ */
+
+#include "cpu.h"
+#include "mutex.h"
+#include "periph/adc.h"
+#include "periph_conf.h"
+#include "xtimer.h"
+
+/**
+ * @brief map CPU specific register/value names
+ */
+#if defined(CPU_MODEL_STM32L476RG)
+#define ADC_CR_REG      CR
+#define ADC_ISR_REG     ISR
+#define ADC_PERIPH_CLK  AHB2
+/* on stm32-l476rg all ADC clocks are are enabled by this bit
+   further clock config is possible over CKMODE[1:0] bits in ADC_CCR reg */
+#define ADC_CLK_EN_MASK   (RCC_AHB2ENR_ADCEN)
+/* refering to Datasheet Section 6.3.18 (ADC characteristics) the minimum
+   achievable sampling rate is 4.21 Msps (12 Bit resolution on slow channel)
+   we use that worst case for configuring the sampling time to be sure it
+   works on all channels.
+   TCONV = Sampling time + 12.5 ADC clock cycles.
+   At 80MHz this means we need to set SMP to 001 (6.5 ADC clock cycles) to
+   stay within specs. (80000000/(6.5+12.5)) = 4210526   */
+#define ADC_SMP_MIN_VAL      (0x1)
+
+/* The sampling time can be specified for each channel over SMPR1 and SMPR2.
+   This specifies the first channel that goes to SMPR2 instead of SMPR1. */
+#define ADC_SMP_BIT_WIDTH    (3)
+
+/* The sampling time can be specified for each channel over SMPR1 and SMPR2.
+   This specifies the first channel that goes to SMPR2 instead of SMPR1. */
+#define ADC_SMPR2_FIRST_CHAN (10)
+#endif
+
+/**
+ * @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[ADC_DEVS];
+
+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(ADC_PERIPH_CLK, ADC_CLK_EN_MASK);
+}
+
+static inline void done(adc_t line)
+{
+/* on STM32L476RG (TODO: maybe true for other L4's? - haven't checked yet)
+   all adc devices are controlled by this one bit.
+   So don't disable the clock as other devices may still use it */
+#if !defined(CPU_MODEL_STM32L476RG)
+    periph_clk_dis(ADC_PERIPH_CLK, ADC_CLK_EN_MASK);
+#endif
+    mutex_unlock(&locks[adc_config[line].dev]);
+}
+
+/**
+ * @brief   Extract the port base address from the given pin identifier
+ */
+static inline GPIO_TypeDef *_port(gpio_t pin)
+{
+    return (GPIO_TypeDef *)(pin & ~(0x0f));
+}
+
+/**
+ * @brief   Extract the pin number from the last 4 bit of the pin identifier
+ */
+static inline int _pin_num(gpio_t pin)
+{
+    return (pin & 0x0f);
+}
+
+int adc_init(adc_t line)
+{
+    /* check if the line is valid */
+    if (line >= ADC_NUMOF) {
+        return -1;
+    }
+
+    /* lock device and enable its peripheral clock */
+    prep(line);
+
+    /* set prescaler to 0 to let the ADC run with maximum speed */
+    ADC123_COMMON->CCR &= ~(ADC_CCR_PRESC);
+
+    /* Setting ADC clock to HCLK/1 is only allowed if AHB clock prescaler is 1*/
+    if (!(RCC->CFGR & RCC_CFGR_HPRE_3)) {
+        /* set ADC clock to HCLK/1 */
+        ADC123_COMMON->CCR |= (ADC_CCR_CKMODE_0);
+    }
+    else {
+        /* set ADC clock to HCLK/2 otherwise */
+        ADC123_COMMON->CCR |= (ADC_CCR_CKMODE_1);
+    }
+
+    /* configure the pin */
+    gpio_init_analog(adc_config[line].pin);
+
+#if defined(CPU_MODEL_STM32L476RG) || defined(CPU_MODEL_STM32L475VG)
+    /* On STM32L475xx/476xx/486xx devices, before any conversion of an input channel coming
+       from GPIO pads, it is necessary to configure the corresponding GPIOx_ASCR register in
+       the GPIO, in addition to the I/O configuration in analog mode. */
+    _port(adc_config[line].pin)->ASCR |= (1 << _pin_num(adc_config[line].pin));
+#endif
+
+    /* init ADC line only if it wasn't already initialized */
+    if (!(dev(line)->ADC_CR_REG & (ADC_CR_ADEN))) {
+        /* reset state of bit DEEPPWD is 1 -> so first leave deep-power down mode */
+        dev(line)->ADC_CR_REG &= ~(ADC_CR_DEEPPWD);
+
+        /* enable ADC internal voltage regulator and wait for startup period */
+        dev(line)->ADC_CR_REG |= (ADC_CR_ADVREGEN);
+        xtimer_usleep(ADC_T_ADCVREG_STUP_US);
+
+        /* configure calibration for single ended input */
+        dev(line)->ADC_CR_REG &= ~(ADC_CR_ADCALDIF);
+
+        /* ´start automatic calibration and wait for it to complete */
+        dev(line)->ADC_CR_REG |= ADC_CR_ADCAL;
+        while (dev(line)->ADC_CR_REG  & ADC_CR_ADCAL) {}
+
+        /* clear ADRDY by writing it*/
+        dev(line)->ADC_ISR_REG |= (ADC_ISR_ADRDY);
+
+        /* enable ADC and wait for it to be ready */
+        dev(line)->ADC_CR_REG |= (ADC_CR_ADEN);
+        while ((dev(line)->ADC_ISR_REG & ADC_ISR_ADRDY) == 0) {}
+
+        /* set sequence length to 1 conversion */
+        dev(line)->SQR1 |= (0 & ADC_SQR1_L);
+    }
+
+    /* configure sampling time for the given channel */
+    if (adc_config[line].chan < ADC_SMPR2_FIRST_CHAN) {
+        dev(line)->SMPR1 =  (ADC_SMP_MIN_VAL << (adc_config[line].chan *
+                                                 ADC_SMP_BIT_WIDTH));
+    }
+    else {
+        dev(line)->SMPR2 =  (ADC_SMP_MIN_VAL << ((adc_config[line].chan -
+                                                  ADC_SMPR2_FIRST_CHAN)
+                                                 * ADC_SMP_BIT_WIDTH));
+    }
+
+    /* 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 & 0x3) {
+        return -1;
+    }
+
+    /* lock and power on the ADC device  */
+    prep(line);
+
+    /* first clear resolution */
+    dev(line)->CFGR &= ~(ADC_CFGR_RES);
+
+    /* then set resolution to the required value*/
+    dev(line)->CFGR |= res;
+
+    /* specify channel for regular conversion */
+    dev(line)->SQR1 = (adc_config[line].chan << ADC_SQR1_SQ1_Pos);
+
+    /* start conversion and wait for it to complete */
+    dev(line)->ADC_CR_REG |= ADC_CR_ADSTART;
+    while (!(dev(line)->ISR & ADC_ISR_EOC)) {}
+
+    /* read the sample */
+    sample = (int)dev(line)->DR;
+
+    /* free the device again */
+    done(line);
+
+    return sample;
+}