Move UART pins initialization later

Fixes #37

Author: facchinm

Diff for: cores/arduino/UART.cpp

@@ -147,13 +147,6 @@ void UartClass::begin(unsigned long baud, uint16_t config)
 
     _written = false;
 
-    //Set up the rx pin
-    pinMode(_hwserial_rx_pin, INPUT_PULLUP);
-
-    //Set up the tx pin
-    digitalWrite(_hwserial_tx_pin, HIGH);
-    pinMode(_hwserial_tx_pin, OUTPUT);
-
     int8_t sigrow_val = SIGROW.OSC16ERR5V;
     baud_setting *= (1024 + sigrow_val);
     baud_setting /= (1024 - abs(sigrow_val));
@@ -169,6 +162,13 @@ void UartClass::begin(unsigned long baud, uint16_t config)
 
     (*_hwserial_module).CTRLA |= USART_RXCIE_bm;
 
+    //Set up the rx pin
+    pinMode(_hwserial_rx_pin, INPUT_PULLUP);
+
+    //Set up the tx pin
+    digitalWrite(_hwserial_tx_pin, HIGH);
+    pinMode(_hwserial_tx_pin, OUTPUT);
+
     // Restore SREG content
     SREG = oldSREG;
 }