Universal Asynchronous Receiver/Transmitter (UART) is a serial, asynchronous communication protocol used by the GPS and XBee modules. Serial communication protocols transfer one bit at a time, as opposed to parallel communication protocols, which use several wires to send multiple bits concurrently. UART is asynchronous because it does not use a clock signal (a constantly alternating sequence of 1s and 0s) to indicate when each bit is being sent. Synchronous communication is accompanied by such a clock signal. Because a clock signal is not used, the two devices must share the same baudrate, the rate at which bits are written and read. UART uses two channels for communication between the microprocessor and the peripheral, one to receive data (RX), and another to transmit data (TX). The connection between two devices is made as shown in the figure below. The RX port of one device connects to the TX port of the other device.
| Microcontroller | Configuration Documentation |
|---|---|
| Arduino | Serial Library |
| PIC32 | PIC32 UART Library |
| Raspberry Pi | UART Configuration, PySerial Library |