make AREF pin optional in SAMD current sensing

Author: runger1101001

src/current_sense/hardware_specific/samd21_mcu.cpp

@@ -137,7 +137,8 @@ float SAMDCurrentSenseADCDMA::toVolts(uint16_t counts) {
 
 void SAMDCurrentSenseADCDMA::initPins(){
 
-  pinMode(pinAREF, INPUT);
+  if (pinAREF>=0)
+    pinMode(pinAREF, INPUT);
   pinMode(pinA, INPUT);
   pinMode(pinB, INPUT);
 
@@ -169,8 +170,10 @@ void SAMDCurrentSenseADCDMA::initADC(){
   //ADC->REFCTRL.bit.REFSEL = ADC_REFCTRL_REFSEL_INTVCC0_Val; //  2.2297 V Supply VDDANA
   ADC->INPUTCTRL.bit.GAIN = ADC_INPUTCTRL_GAIN_1X_Val; // Gain select as 1X
   // ADC->INPUTCTRL.bit.GAIN = ADC_INPUTCTRL_GAIN_DIV2_Val;  // default
-  ADC->REFCTRL.bit.REFSEL = ADC_REFCTRL_REFSEL_AREFA;
-  // ADC->REFCTRL.bit.REFSEL = ADC_REFCTRL_REFSEL_INTVCC0;
+  if (pinAREF>=0)
+    ADC->REFCTRL.bit.REFSEL = ADC_REFCTRL_REFSEL_AREFA;
+  else
+    ADC->REFCTRL.bit.REFSEL = ADC_REFCTRL_REFSEL_INTVCC0;
   ADCsync();  //  ref 31.6.16
 
   /*

src/current_sense/hardware_specific/samd21_mcu.h

@@ -3,7 +3,7 @@
 #ifndef CURRENT_SENSE_SAMD21_H
 #define CURRENT_SENSE_SAMD21_H
 
-// #define SIMPLEFOC_SAMD_DEBUG
+#define SIMPLEFOC_SAMD_DEBUG
 #if !defined(SIMPLEFOC_SAMD_DEBUG_SERIAL)
 #define SIMPLEFOC_SAMD_DEBUG_SERIAL Serial
 #endif
@@ -18,6 +18,8 @@
   } dmacdescriptor ;
 
 
+// AREF pin is 42
+
 class SAMDCurrentSenseADCDMA
 {
 
@@ -64,4 +66,4 @@ class SAMDCurrentSenseADCDMA
 
 
 
-#endif
+#endif