The Serial API is capable of exchanging data with PCs and other devices. Set up the same baud rate as the remote device using begin() to exchange data using read() and write(). 

LinkIt provides 2 sets of UART, the physical UART (pin 0 and 1) and USB UART. When a LinkIt board is connected to a PC using a USB cable, the COM port seen in the IDE is USB UART, not the physical UART (pin 0 and 1). On the PC the port will be identified as MTK USB Modem Port in device Manager. 

The Serial object corresponds to the USB UART. To read from and write to the physical UART (pins 0 and 1), use the Serial1 object instead, as shown in Table below. 

Table : Mapping of UARTs to Serial objects