cores/arduino/wiring_analog.c

@@ -11,6 +11,11 @@ extern "C" {
 extern void ErrorMsgHandler(const char * msg);
 
 // -------------------------- Analog read -------------------------- //
+#define ADC_SAMPLES_QTY           10  // samples quantity for averaging adc results
+#define ADC_DEFAULT_RESOLUTION    10  // resolution for arduino compatibility
+
+uint8_t currentResolution = ADC_DEFAULT_RESOLUTION; // resolution used for output results
+
 // structure for ADC channel initialization. Only the channel number 
 // changes, everything else is the same
 static ADC_HandleTypeDef hadc = 
@@ -21,6 +26,16 @@ static ADC_HandleTypeDef hadc =
   .Init.Sel    = 0
 };
 
+void analogReadResolution(uint8_t resolution)
+{
+  // resolution limits
+  if (resolution > 32) resolution = 32;
+  if (resolution < 1)  resolution = 1;
+
+  // save new resolution
+  currentResolution = resolution;
+}
+
 // initialize the channel, run a single measurement, wait for the result
 uint32_t analogRead(uint32_t PinNumber)
 {
@@ -44,11 +59,31 @@ uint32_t analogRead(uint32_t PinNumber)
     hadc.Init.Sel = adcChannel;
     HAL_ADC_Init(&hadc);
 
-    // start the conversion twice in case another channel was polled before
+    // start the dummy conversion in case another channel was polled before
     HAL_ADC_SINGLE_AND_SET_CH(hadc.Instance, adcChannel);
-    value = HAL_ADC_WaitAndGetValue(&hadc);
-    HAL_ADC_Single(&hadc);
-    value = HAL_ADC_WaitAndGetValue(&hadc);
+    HAL_ADC_WaitAndGetValue(&hadc);
+
+    // accumulate results
+    uint32_t acc = 0;
+    for (uint8_t i = 0; i<ADC_SAMPLES_QTY; i++)
+    {
+      HAL_ADC_Single(&hadc);
+      acc += HAL_ADC_WaitAndGetValue(&hadc);
+    }
+    // get value by averaging with MCU_ADC_RESOLUTION
+    value = acc/ADC_SAMPLES_QTY;
+
+    // map value to selected resolution
+    if (currentResolution > MCU_ADC_RESOLUTION)
+    {
+      // extra least significant bits are padded with zeros
+      value = (value << (currentResolution - MCU_ADC_RESOLUTION));
+    }
+    else
+    {
+      // extra least significant bits read from the ADC are discarded
+      value = (value >> (MCU_ADC_RESOLUTION - currentResolution));
+    }
   }
   else
     ErrorMsgHandler("analogRead(): invalid analog pin number");

cores/arduino/wiring_analog.h

@@ -16,6 +16,13 @@ extern "C" {
  */
 uint32_t analogRead(uint32_t PinNumber);
 
+/*
+ * \brief Set the resolution of adc results. Default is 10 bits (range from 0 to 1023).
+ *
+ * \param resolution 1...32
+ */
+void analogReadResolution(uint8_t resolution);
+
 /*
  * \brief Writes an analog value (PWM wave) to a pin.
  *

variants/standart/pins_arduino.h

@@ -71,6 +71,7 @@ volatile uint32_t* portInputRegister(GPIO_TypeDef* GPIO_x);
 #define SERIAL_PORT_QTY 2
 
 // ADC
+#define MCU_ADC_RESOLUTION    12 // bits
 // determines the ADC channel number by the board pin number
 uint32_t analogInputToChannelNumber(uint32_t PinNumber);