Fix warnings in SPI library

Author: facchinm

libraries/SPI/src/SPI.cpp

@@ -131,7 +131,7 @@ void SPIClass::detachMaskedInterrupts() {
   uint8_t shift = 0;
   while (temp != 0) {
     if (temp & 1) {
-      uint8_t* pin_ctrl_reg = getPINnCTRLregister(portToPortStruct(shift/8), shift%8);
+      volatile uint8_t* pin_ctrl_reg = getPINnCTRLregister(portToPortStruct(shift/8), shift%8);
       irqMap[shift] = *pin_ctrl_reg;
       *pin_ctrl_reg &= ~(PORT_ISC_gm);
     }
@@ -142,7 +142,7 @@ void SPIClass::detachMaskedInterrupts() {
   shift = 32;
   while (temp != 0) {
     if (temp & 1) {
-      uint8_t* pin_ctrl_reg = getPINnCTRLregister(portToPortStruct(shift/8), shift%8);
+      volatile uint8_t* pin_ctrl_reg = getPINnCTRLregister(portToPortStruct(shift/8), shift%8);
       irqMap[shift] = *pin_ctrl_reg;
       *pin_ctrl_reg &= ~(PORT_ISC_gm);
     }
@@ -156,7 +156,7 @@ void SPIClass::reattachMaskedInterrupts() {
   uint8_t shift = 0;
   while (temp != 0) {
     if (temp & 1) {
-      uint8_t* pin_ctrl_reg = getPINnCTRLregister(portToPortStruct(shift/8), shift%8);
+      volatile uint8_t* pin_ctrl_reg = getPINnCTRLregister(portToPortStruct(shift/8), shift%8);
       *pin_ctrl_reg |= irqMap[shift];
     }
     temp = temp >> 1;
@@ -166,7 +166,7 @@ void SPIClass::reattachMaskedInterrupts() {
   shift = 32;
   while (temp != 0) {
     if (temp & 1) {
-      uint8_t* pin_ctrl_reg = getPINnCTRLregister(portToPortStruct(shift/8), shift%8);
+      volatile uint8_t* pin_ctrl_reg = getPINnCTRLregister(portToPortStruct(shift/8), shift%8);
       *pin_ctrl_reg |= irqMap[shift];
     }
     temp = temp >> 1;

libraries/SPI/src/SPI.h

@@ -48,7 +48,9 @@
 #define SPI_INTERRUPT_DISABLE     0
 #define SPI_INTERRUPT_ENABLE      1
 
+#ifndef EXTERNAL_NUM_INTERRUPTS
 #define EXTERNAL_NUM_INTERRUPTS   NUM_TOTAL_PINS
+#endif
 
 class SPISettings {
   public: