add samd51 support, fixes PaulStoffregen#32

CapacitiveSensor.h

@@ -236,6 +236,17 @@ void directModeOutput(IO_REG_TYPE pin)
 #define DIRECT_WRITE_LOW(base, mask)    ((*((base)+5)) = (mask))
 #define DIRECT_WRITE_HIGH(base, mask)   ((*((base)+6)) = (mask))
 
+#elif defined(__SAMD51__)
+#define PIN_TO_BASEREG(pin)             portModeRegister(digitalPinToPort(pin))
+#define PIN_TO_BITMASK(pin)             (digitalPinToBitMask(pin))
+#define IO_REG_TYPE uint32_t
+#define IO_REG_ASM
+#define DIRECT_READ(base, mask)         (((*((base)+8)) & (mask)) ? 1 : 0) // IN
+#define DIRECT_MODE_INPUT(base, mask)   ((*((base)+1)) = (mask)) // DIRCLR
+#define DIRECT_MODE_OUTPUT(base, mask)  ((*((base)+2)) = (mask)) // DIRSET
+#define DIRECT_WRITE_LOW(base, mask)    ((*((base)+5)) = (mask)) // OUTCLR
+#define DIRECT_WRITE_HIGH(base, mask)   ((*((base)+6)) = (mask)) /// OUTSET
+
 #elif defined(RBL_NRF51822)
 #define PIN_TO_BASEREG(pin)             (0)
 #define PIN_TO_BITMASK(pin)             (pin)