Understanding UART and Serial Communication

UART (Universal Asynchronous Receiver/Transmitter) is a hardware communication protocol used for serial communication between two devices. It enables asynchronous data exchange, meaning devices don’t need to share a clock signal—just a common baud rate.

UART converts parallel data from a microcontroller into a serial stream of bits, transmitting one bit at a time. Each data packet typically includes:

• Start Bit: Signals the beginning of data transmission.
• Data Bits: Usually 5 to 9 bits representing the actual data.
• Optional Parity Bit: Provides basic error checking.
• Stop Bit(s): Marks the end of the packet.

For example, sending the ASCII letter ‘A’ (binary 01000001) at 9600 baud with 8 data bits, no parity, and 1 stop bit (8N1) would look like:
[Start][01000001][Stop]

Baud rate is the speed of communication, measured in bits per second (bps). Both transmitter and receiver must use the same baud rate (e.g., 9600, 115200).

UART requires two main wires:

• TX (Transmit): Sends data.
• RX (Receive): Receives data.

These lines are connected crosswise: Device A’s TX connects to Device B’s RX and vice versa.

Unlike SPI or I²C, UART doesn’t use a clock line. Timing is managed internally based on agreed settings, which simplifies wiring but requires precise baud rate matching.

UART is widely used in embedded systems, sensor modules, GPS, Bluetooth modules, and debugging. It’s popular because of its simplicity and low overhead.

• Generally supports only two devices (point-to-point).
• Cable length and noise can limit communication reliability.
• Not ideal for high-speed or multi-device networks.

More Labs To Love:

Interactive Logic Gate Simulator Lab
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More on UART: Wikipedia