Merge pull request #4221 from DipSwitch/stm32f1_adc_implementation

cpu/stm32f1/periph/adc: ADC implementation for STM32F1

boards/fox/include/periph_conf.h

@@ -43,6 +43,13 @@ extern "C" {
 #define CLOCK_FLASH_LATENCY FLASH_ACR_LATENCY_2
 /** @} */
 
+/**
+ * @name ADC configuration
+ * @{
+ */
+#define ADC_NUMOF           (0)
+/** @} */
+
 /**
  * @brief Timer configuration
  * @{

boards/iotlab-m3/include/periph_conf.h

@@ -44,6 +44,18 @@ extern "C" {
 #define CLOCK_FLASH_LATENCY FLASH_ACR_LATENCY_2
 /** @} */
 
+/**
+ * @name ADC configuration
+ * @{
+ */
+#define ADC_CONFIG          {       \
+    { GPIO_PIN(PORT_A,3), 0, 3  },  \
+    { GPIO_UNDEF        , 0, 16 },  \
+    { GPIO_UNDEF        , 0, 17 } }
+
+#define ADC_NUMOF           (3)
+/** @} */
+
 /**
  * @brief Timer configuration
  * @{

boards/nucleo-f103/include/periph_conf.h

@@ -45,6 +45,13 @@ extern "C" {
 #define CLOCK_FLASH_LATENCY FLASH_ACR_LATENCY_2    /* for >= 72 MHz */
 /** @} */
 
+/**
+ * @name ADC configuration
+ * @{
+ */
+#define ADC_NUMOF           (0)
+/** @} */
+
 /**
  * @brief Timer configuration
  * @{

boards/spark-core/include/periph_conf.h

@@ -43,6 +43,13 @@
 #define CLOCK_FLASH_LATENCY FLASH_ACR_LATENCY_2
 /** @} */
 
+/**
+ * @name ADC configuration
+ * @{
+ */
+#define ADC_NUMOF           (0)
+/** @} */
+
 /**
  * @brief Timer configuration
  * @{

cpu/stm32f1/include/periph_cpu.h

@@ -25,6 +25,11 @@
 extern "C" {
 #endif
 
+/**
+ * @brief   Available number of ADC devices
+ */
+#define ADC_DEVS            (2U)
+
 /**
  * @brief   Overwrite the default gpio_t type definition
  * @{
@@ -101,6 +106,15 @@ typedef enum {
     GPIO_AF_OUT_OD = 0xf,   /**< alternate function output - open-drain */
 } gpio_af_out_t;
 
+/**
+ * @brief   ADC channel configuration data
+ */
+typedef struct {
+    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;
+
 /**
  * @brief   Timer configuration
  */
@@ -121,6 +135,13 @@ typedef struct {
  */
 void gpio_init_af(gpio_t pin, gpio_af_out_t af);
 
+/**
+ * @brief   Configure the given pin to be used as ADC input
+ *
+ * @param[in] pin       pin to configure
+ */
+void gpio_init_analog(gpio_t pin);
+
 #ifdef __cplusplus
 }
 #endif

cpu/stm32f1/periph/adc.c

@@ -0,0 +1,161 @@
+/*
+ * Copyright (C) 2016 Engineering-Spirit
+ *
+ * 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_stm32f1
+ * @{
+ *
+ * @file
+ * @brief       Low-level ADC driver implementation
+ *
+ * @author      Hauke Petersen <hauke.petersen@fu-berlin.de>
+ * @author      Nick van IJzendoorn <nijzendoorn@engineering-spirit.nl>
+ *
+ * @}
+ */
+
+#include "cpu.h"
+#include "mutex.h"
+#include "periph/adc.h"
+#include "periph_conf.h"
+
+/**
+ * @brief   Maximum allowed ADC clock speed
+ */
+#define MAX_ADC_SPEED           (14000000U)
+
+/**
+ * @brief   Load the ADC configuration
+ * @{
+ */
+#ifdef ADC_CONFIG
+static const adc_conf_t adc_config[] = ADC_CONFIG;
+#else
+static const adc_conf_t adc_config[] = {};
+#endif
+
+/**
+ * @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]);
+    RCC->APB2ENR |= (RCC_APB2ENR_ADC1EN << adc_config[line].dev);
+}
+
+static inline void done(adc_t line)
+{
+    RCC->APB2ENR &= ~(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 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;
+        }
+    }
+    RCC->CFGR &= ~(RCC_CFGR_ADCPRE);
+    RCC->CFGR |= ((clk_div / 2) - 1) << 14;
+
+    /* enable the ADC module */
+    dev(line)->CR2 |= ADC_CR2_ADON;
+
+    /* resets the selected ADC calibration registers */
+    dev(line)->CR2 |= ADC_CR2_RSTCAL;
+    /* check the status of RSTCAL bit */
+    while (dev(line)->CR2 & ADC_CR2_RSTCAL) {}
+
+    /* enable the selected ADC calibration process */
+    dev(line)->CR2 |= ADC_CR2_CAL;
+    /* wait for the calibration to have finished */
+    while (dev(line)->CR2 & ADC_CR2_CAL) {}
+
+    /* set all channels to maximum (239.5) cycles for best accuracy */
+    dev(line)->SMPR1 |= 0x00ffffff;
+    dev(line)->SMPR2 |= 0x3fffffff;
+    /* we want to sample one channel */
+    dev(line)->SQR1 = ADC_SQR1_L_0;
+    /* start sampling from software */
+    dev(line)->CR2 |= ADC_CR2_EXTTRIG | ADC_CR2_EXTSEL;
+
+    /* 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) {
+        /* check if the internal channels are configured to use ADC1 */
+        if (dev(line) != ADC1) {
+            return -3;
+        }
+
+        dev(line)->CR2 |= ADC_CR2_TSVREFE;
+    }
+
+    /* free the device again */
+    done(line);
+    return 0;
+}
+
+int adc_sample(adc_t line, adc_res_t res)
+{
+    int sample;
+
+    /* check if the linenel is valid */
+    if (line >= ADC_NUMOF) {
+        return -1;
+    }
+
+    /* check if resolution is applicable */
+    if (res != ADC_RES_12BIT) {
+        return -2;
+    }
+
+    /* lock and power on the ADC device  */
+    prep(line);
+
+    /* set conversion channel */
+    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;
+}

cpu/stm32f1/periph/gpio.c

@@ -150,6 +150,16 @@ void gpio_init_af(gpio_t pin, gpio_af_out_t af)
     port->CR[pin_num >> 3] |=  (af << ((pin_num & 0x7) * 4));
 }
 
+void gpio_init_analog(gpio_t pin)
+{
+    /* enable the GPIO port RCC */
+    RCC->APB2ENR |= (RCC_APB2ENR_IOPAEN << _port_num(pin));
+
+    /* map the pin as analog input */
+    int pin_num = _pin_num(pin);
+    _port(pin)->CR[pin_num >= 8] &= ~(0xfl << (4 * (pin_num - ((pin_num >= 8) * 8))));
+}
+
 void gpio_irq_enable(gpio_t pin)
 {
     EXTI->IMR |= (1 << _pin_num(pin));