What are UARTs (Universal Asynchronous Receiver/Transmitter)?

UARTs (Universal Asynchronous Receiver/Transmitters) are hardware circuits that transform parallel data from a microcontroller or CPU into serial data for transmission, or convert incoming serial data into parallel data for another microcontroller or CPU. UARTs can utilize RS232, RS422, or RS485 protocols for communication. When choosing a UART, consider factors such as the number of channels, data rate, and additional features like internal oscillators, timers, counters, GPIO, and printer ports.

How UART Works

The UART responsible for data transmission receives data from a data bus. This data bus is used to send data from another device, such as a CPU, memory, or microcontroller, to the UART. Initially, the data is transferred in parallel form from the data bus to the transmitting UART. Once the UART receives this parallel data, it adds a start bit, a parity bit, and a stop bit to form a complete data packet. This packet is then transmitted serially, bit by bit, through the Tx pin. The receiving UART captures the data packet bit by bit at its Rx pin. It then converts the serial data back into parallel form, stripping away the start bit, parity bit, and stop bits. Finally, the receiving UART sends the parallel data back to the data bus on the receiving end.