Bug fix: check for activity on double bonded pins

Author: Roy, Elizabeth

cores/arduino/wiring_analog.c

@@ -69,6 +69,9 @@ void analogReference(uint8_t mode)
 int analogRead(uint8_t pin)
 {
 	if(pin > NUM_ANALOG_INPUTS) return NOT_A_PIN;
+	
+	/* Check if TWI is operating on double bonded pin */
+	if(((pin == PIN_A4) || (pin == PIN_A5)) && (TWI0.MCTRLA & TWI_ENABLE_bm)) return 0;
 
 	uint8_t low, high;
 
@@ -117,6 +120,9 @@ void analogWrite(uint8_t pin, int val)
 	uint8_t bit_pos  = digitalPinToBitPosition(pin);
 	if(bit_pos == NOT_A_PIN) return;
 
+	/* Special check for SPI_SS double bonded pin -- no action if SPI is active */
+	if((pin == 10) && (SPI0.CTRLB & SPI_SSD_bm)) return;
+
 	// We need to make sure the PWM output is enabled for those pins
 	// that support it, as we turn it off when digitally reading or
 	// writing with them.  Also, make sure the pin is in output mode