Implement initial ADC support

* Add simple ADC driver, with support for ADC1 and all channels.
* Export MicroPython ADC object with read_channel function.
* Add stm32f4xx_adc.c and adc.c to Makefile.

stm/Makefile

@@ -57,6 +57,7 @@ SRC_C = \
 	pybwlan.c \
 	i2c.c \
 	usrsw.c \
+	adc.c \
 
 SRC_S = \
 	startup_stm32f40xx.s \
@@ -100,6 +101,7 @@ SRC_STM = \
 	usbd_storage_msd.c \
 	stm324x7i_eval.c \
 	stm324x7i_eval_sdio_sd.c \
+	stm32f4xx_adc.c \
 
 #SRC_STM_OTG = \
 #	usb_hcd.c \

stm/adc.c

+#include <stdio.h>
+#include <stm32f4xx_rcc.h>
+#include <stm32f4xx_gpio.h>
+#include <stm32f4xx_adc.h>
+
+#include "misc.h"
+#include "mpconfig.h"
+#include "obj.h"
+#include "adc.h"
+
+/* ADC defintions */
+#define ADCx                (ADC1)
+#define ADCx_CLK            (RCC_APB2Periph_ADC1)
+#define ADC_NUM_CHANNELS    (16)
+
+/* GPIO struct */
+typedef struct {
+    GPIO_TypeDef* port;
+    uint32_t pin;
+} gpio_t;
+
+/* ADC GPIOs */
+static gpio_t adc_gpio[] = {
+    {GPIOA, GPIO_Pin_0},    /* ADC123_IN0 */
+    {GPIOA, GPIO_Pin_1},    /* ADC123_IN1 */
+    {GPIOA, GPIO_Pin_2},    /* ADC123_IN2 */
+    {GPIOA, GPIO_Pin_3},    /* ADC123_IN3 */
+    {GPIOA, GPIO_Pin_4},    /* ADC12_IN4 */
+    {GPIOA, GPIO_Pin_5},    /* ADC12_IN5 */
+    {GPIOA, GPIO_Pin_6},    /* ADC12_IN6 */
+    {GPIOA, GPIO_Pin_7},    /* ADC12_IN7 */
+    {GPIOB, GPIO_Pin_0},    /* ADC12_IN8 */
+    {GPIOB, GPIO_Pin_1},    /* ADC12_IN9 */
+    {GPIOC, GPIO_Pin_0},    /* ADC123_IN10 */
+    {GPIOC, GPIO_Pin_1},    /* ADC123_IN11 */
+    {GPIOC, GPIO_Pin_2},    /* ADC123_IN12 */
+    {GPIOC, GPIO_Pin_3},    /* ADC123_IN13 */
+    {GPIOC, GPIO_Pin_4},    /* ADC12_IN14 */
+    {GPIOC, GPIO_Pin_5},    /* ADC12_IN15 */
+
+};
+
+void adc_init(uint32_t resolution) {
+  ADC_InitTypeDef       ADC_InitStructure;
+  GPIO_InitTypeDef      GPIO_InitStructure;
+  ADC_CommonInitTypeDef ADC_CommonInitStructure;
+
+  /* Enable ADCx, DMA and GPIO clocks */ 
+#if 0
+  /* GPIO clocks enabled in main */
+  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA |
+                         RCC_AHB1Periph_GPIOB |
+                         RCC_AHB1Periph_GPIOC, ENABLE);
+#endif
+  RCC_APB2PeriphClockCmd(ADCx_CLK, ENABLE);
+
+  /* ADC Common Init */
+  ADC_CommonInitStructure.ADC_Mode = ADC_Mode_Independent;
+  ADC_CommonInitStructure.ADC_Prescaler = ADC_Prescaler_Div2;
+  ADC_CommonInitStructure.ADC_DMAAccessMode = ADC_DMAAccessMode_Disabled;
+  ADC_CommonInitStructure.ADC_TwoSamplingDelay = ADC_TwoSamplingDelay_5Cycles;
+  ADC_CommonInit(&ADC_CommonInitStructure);
+
+  /* Configure ADC GPIOs */
+  for (int i=0; i<ADC_NUM_CHANNELS; i++) {
+      GPIO_InitStructure.GPIO_Pin = adc_gpio[i].pin;
+      GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;
+      GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
+      GPIO_Init(adc_gpio[i].port, &GPIO_InitStructure);
+  }
+
+  /* ADCx Init */
+//  ADC_DeInit();
+  ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;
+  ADC_InitStructure.ADC_ScanConvMode = DISABLE;
+  ADC_InitStructure.ADC_ContinuousConvMode = DISABLE;
+  ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_None;
+  ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T1_CC1;
+  ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
+  ADC_InitStructure.ADC_NbrOfConversion = 1;
+  ADC_Init(ADCx, &ADC_InitStructure);
+
+  /* Enable ADCx */
+  ADC_Cmd(ADCx, ENABLE);
+}
+
+uint32_t adc_read_channel(int channel)
+{
+    int timeout = 10000;
+
+    if (channel > (ADC_NUM_CHANNELS-1)) {
+        return 0;
+    }
+
+    /* ADC regular channel config ADC/Channel/SEQ Rank/Sample time */
+    ADC_RegularChannelConfig(ADCx, channel, 1, ADC_SampleTime_3Cycles);
+
+    /* Start ADC single conversion */
+    ADC_SoftwareStartConv(ADCx);
+
+    /* Wait for conversion to be complete*/
+    while(!ADC_GetFlagStatus(ADCx, ADC_FLAG_EOC) && --timeout >0) {
+    }
+
+    /* ADC conversion timed out */ 
+    if (timeout == 0) {
+        return 0;
+    }
+
+    /* Return converted data */
+    return ADC_GetConversionValue(ADCx); 
+}
+
+/******************************************************************************/
+/* Micro Python bindings                                                      */
+
+typedef struct _pyb_adc_obj_t {
+    mp_obj_base_t base;
+    int adc_id;
+    bool is_enabled;
+} pyb_adc_obj_t;
+
+static mp_obj_t adc_obj_read_channel(mp_obj_t self_in, mp_obj_t channel) {
+    mp_obj_t ret = mp_const_none;
+    pyb_adc_obj_t *self = self_in;
+
+    if (self->is_enabled) {
+        uint32_t chan = mp_obj_get_int(channel);
+        uint32_t data = adc_read_channel(chan);
+        ret = mp_obj_new_int(data);
+    }
+    return ret;
+}
+
+static void adc_obj_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in) {
+    pyb_adc_obj_t *self = self_in;
+    print(env, "<ADC %lu>", self->adc_id);
+}
+
+static MP_DEFINE_CONST_FUN_OBJ_2(adc_obj_read_channel_obj, adc_obj_read_channel);
+
+static const mp_method_t adc_methods[] = {
+    { "read_channel",   &adc_obj_read_channel_obj},
+    { NULL, NULL },
+};
+
+static const mp_obj_type_t adc_obj_type = {
+    { &mp_const_type },
+    "ADC",
+    .print = adc_obj_print,
+    .methods = adc_methods,
+};
+
+mp_obj_t pyb_ADC(mp_obj_t resolution) {
+    /* init ADC */
+    adc_init(mp_obj_get_int(resolution));
+
+    pyb_adc_obj_t *o = m_new_obj(pyb_adc_obj_t);
+    o->base.type = &adc_obj_type;
+    o->adc_id = 1;
+    o->is_enabled = true;
+    return o;
+}

stm/adc.h

+mp_obj_t pyb_ADC(mp_obj_t resolution);

stm/main.c

@@ -40,6 +40,7 @@
 #include "pybwlan.h"
 #include "i2c.h"
 #include "usrsw.h"
+#include "adc.h"
 
 int errno;
 
@@ -839,6 +840,7 @@ soft_reset:
         rt_store_attr(m, qstr_from_str_static("I2C"), rt_make_function_n(2, pyb_I2C));
         rt_store_attr(m, qstr_from_str_static("gpio"), (mp_obj_t)&pyb_gpio_obj);
         rt_store_attr(m, qstr_from_str_static("Usart"), rt_make_function_n(2, pyb_Usart));
+        rt_store_attr(m, qstr_from_str_static("ADC"), rt_make_function_n(1, pyb_ADC));
         rt_store_name(qstr_from_str_static("pyb"), m);
 
         rt_store_name(qstr_from_str_static("open"), rt_make_function_n(2, pyb_io_open));