fixes according to @iabdalkader review

Author: leonardocavagnis

src/AdvancedADC.cpp

@@ -22,6 +22,7 @@
 #include "AdvancedADC.h"
 
 #define ADC_NP  ((ADCName) NC)
+#define ADC_PIN_ALT_MASK    (uint32_t) (ALT0 | ALT1 )
 
 struct adc_descr_t {
     ADC_HandleTypeDef adc;
@@ -126,10 +127,11 @@ int AdvancedADC::begin(uint32_t resolution, uint32_t sample_rate, size_t n_sampl
     for (size_t i=0; i<n_channels; i++) {
         adc_pins[i] =  (PinName) (adc_pins[i] & ~(ADC_PIN_ALT_MASK));
     }
+    
     // Find an ADC that can be used with these set of pins/channels.
-    for (size_t i=0; instance == ADC_NP && i<AN_ARRAY_SIZE(pin_alt); i++) {
+    for (size_t i=0; instance == ADC_NP && i<AN_ARRAY_SIZE(adc_pin_alt); i++) {
         // Calculate alternate function pin.
-        PinName pin = (PinName) (adc_pins[0] | pin_alt[i]); // First pin decides the ADC.
+        PinName pin = (PinName) (adc_pins[0] | adc_pin_alt[i]); // First pin decides the ADC.
 
         // Check if pin is mapped.
         if (pinmap_find_peripheral(pin, PinMap_ADC) == NC) {
@@ -140,7 +142,7 @@ int AdvancedADC::begin(uint32_t resolution, uint32_t sample_rate, size_t n_sampl
         for (size_t j=0; instance == ADC_NP && j<AN_ARRAY_SIZE(adc_descr_all); j++) {
             descr = &adc_descr_all[j];
             if (descr->pool == nullptr) {
-                ADCName tmp_instance = pinmap_peripheral(pin, PinMap_ADC);
+                ADCName tmp_instance = (ADCName) pinmap_peripheral(pin, PinMap_ADC);
                 if (descr->adc.Instance == ((ADC_TypeDef*) tmp_instance)) {
                     instance = tmp_instance;
                     adc_pins[0] = pin;
@@ -159,9 +161,9 @@ int AdvancedADC::begin(uint32_t resolution, uint32_t sample_rate, size_t n_sampl
     pinmap_pinout(adc_pins[0], PinMap_ADC);
     uint8_t ch_init = 1;
     for (size_t i=1; i<n_channels; i++) {
-        for (size_t j=0; j<AN_ARRAY_SIZE(pin_alt); j++) {
+        for (size_t j=0; j<AN_ARRAY_SIZE(adc_pin_alt); j++) {
             // Calculate alternate function pin.
-            PinName pin = (PinName) (adc_pins[i] | pin_alt[j]);
+            PinName pin = (PinName) (adc_pins[i] | adc_pin_alt[j]);
             // Check if pin is mapped.
             if (pinmap_find_peripheral(pin, PinMap_ADC) == NC) {
                 break;