USB to Multi-Protocol Serial Adapter: RS-232 / TTL UART / RS-485

Jargon buster

Plain-language definitions for the technical terms used above.

baud

Baud is the signalling rate of a serial connection, often used as the speed setting for UART communication. Matching the baud rate matters because both connected devices must use the same setting for readable data.

COM port

A COM port is how a computer (chiefly under Windows) presents a serial port to software, whether a physical RS-232 port or a virtual port created when a USB-to-serial device is plugged in. Software can then communicate with the connected device over serial using a terminal or configuration program.

GND

GND is the ground or reference connection (0 V) for a circuit. When connecting two devices together, their grounds must be joined so both agree on what counts as a low or high signal.

LED

A light-emitting diode (LED) is a small electronic component that emits light when current flows through it in the correct direction. Because it only conducts one way, its polarity matters, and a through-hole LED must be soldered the correct way around to light up.

RS-232

RS-232 is an older serial communication standard that uses higher, inverted signal voltages (typically around plus or minus 3 to 15 volts) rather than the low logic levels of modern microcontroller pins. When connecting RS-232 equipment to a microcontroller, you usually need an RS-232 transceiver or level converter rather than wiring it directly, or you risk damaging the pins.

RS485

RS485 is a robust differential serial communication standard often used in factories, farms and buildings where cables may be long or electrically noisy, and it can link many devices on a single pair of wires. When a product lists RS485, it can communicate with industrial sensors, meters and control equipment over longer distances than typical hobby serial wiring.

RX

RX means receive, usually showing data being received by the board. An RX indicator LED can help with troubleshooting USB or serial communication.

TX

TX means transmit, usually showing data being sent from the board. A TX indicator LED can help you see when the board is communicating or uploading code.

UART

UART is a simple asynchronous serial interface that sends data over separate transmit and receive wires, usually labelled TX and RX, with both ends set to the same baud rate. It is a common way for microcontrollers and other serial devices to exchange data.

USB to serial converter

A chip that converts a USB connection into the serial (UART) signals a microcontroller understands. A board that includes one usually appears to a computer as a serial port for programming and debugging, rather than as a native USB device such as a keyboard or mass-storage drive.