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Hardware & devices

UART

A hardware block that sends and receives bytes as asynchronous serial data over two wires, the basis of classic serial ports, debug consoles and many modem interfaces.

A UART (Universal Asynchronous Receiver/Transmitter) converts bytes into a stream of bits on a transmit line and reassembles bytes from a receive line, with no shared clock; both sides simply agree on a baud rate and framing. Firmware prints its debug log over a UART, GPS receivers stream position sentences over one, and cellular and LoRa IoT modules accept AT commands over one.

Its simplicity is its strength: two wires, no addressing, easy to tap with a cheap adapter. That is also a security concern, since an exposed debug UART on a production board can hand an attacker a root shell, which is why hardening guides tell manufacturers to disable or lock it. For speed and multiple devices on one bus, SPI and I2C take over; for distance, UART signals are usually converted to RS-485.

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