Small SPI lib fix, add SWO pin to variant header

Author: PaintYourDragon

libraries/SPI/SPI.cpp

@@ -321,7 +321,7 @@ void SPIClass::transfer(const void* txbuf, void* rxbuf, size_t count,
             bool blockThisPass;
             if(count > 65535) { // Too big for 1 descriptor
                 blockThisPass = true;
-                bytesThisPass = count % 65535; // Fractional part
+                bytesThisPass = count & 65535; // Fractional part
                 if(!bytesThisPass) bytesThisPass = 65535;
             } else {
                 blockThisPass = block;

variants/grand_central_m4/variant.cpp

@@ -181,6 +181,8 @@ const PinDescription g_APinDescription[]=
   // ----------------------
   // 95 SD detect
   { PORTB, 31, PIO_DIGITAL, PIN_ATTR_DIGITAL, No_ADC_Channel, NOT_ON_PWM, NOT_ON_TIMER, EXTERNAL_INT_15 },
+  // 96 SWO (on debug header)
+  { PORTB, 30, PIO_DIGITAL, PIN_ATTR_DIGITAL, No_ADC_Channel, NOT_ON_PWM, NOT_ON_TIMER, EXTERNAL_INT_14 },
 } ;
 
 const void* g_apTCInstances[TCC_INST_NUM+TC_INST_NUM]={ TCC0, TCC1, TCC2, TCC3, TCC4, TC0, TC1, TC2, TC3, TC4, TC5, TC6, TC7 } ;