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UART Universal asynchronous receiver and transmitter

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UART (Universal Asynchronous Receiver and Transmitter) is a widely used serial communication protocol used to transmit and receive data between electronic devices. It serves as a fundamental method for inter-device communication in many embedded systems, microcontrollers, and computer peripherals. UART is "asynchronous" because the data is sent without a shared clock signal between the sender and receiver.

Key Features of UART:

  1. Asynchronous Communication: In UART, data is transmitted without the need for a shared clock signal between the sender (transmitter) and the receiver. Instead, both devices agree on a specific baud rate, which defines the data transmission speed. The baud rate indicates how many bits are transmitted per second.
  2. Start and Stop Bits: To synchronize the data transmission, each data byte in UART is framed by a start bit and one or more stop bits. The start bit signals the beginning of a data byte, while the stop bit(s) signal the end of the data byte and allow the receiver to detect the byte boundaries.
  3. Data Frame: A typical UART data frame consists of a start bit, a fixed number of data bits (usually 8 bits but can be configured for different data sizes), an optional parity bit (for error checking), and one or more stop bits.
  4. Asynchronous Communication: The lack of a shared clock signal means that both the transmitter and receiver must agree on the same baud rate to ensure data is correctly interpreted. If the baud rates don't match, data errors can occur.

UART Operation:

The UART communication process involves the following steps:

Transmitter Operation:

  • The UART transmitter (TX) receives data to be sent from the device's data bus or register.
  • The data is converted into a series of bits and framed with a start bit, data bits, optional parity bit, and stop bit(s).
  • The TX pin transmits the framed data serially (one bit at a time) to the receiving device.

Receiver Operation:

  • The UART receiver (RX) continuously monitors the RX pin for incoming data.
  • When a start bit is detected, the receiver starts sampling the incoming bits based on the agreed-upon baud rate.
  • The receiver reconstructs the data byte by concatenating the sampled bits, excluding the start and stop bits.

Baud Rate Synchronization:

  • For successful communication, both the transmitter and receiver must operate at the same baud rate. If the rates differ, data integrity can be compromised.
  • When setting up UART communication between devices, configuring the same baud rate on both ends is essential.

Flow Control (Optional):

  • UART communication can include optional hardware or software flow control mechanisms (e.g., RTS/CTS or XON/XOFF) to manage data flow between devices to avoid data overflows or underflows.

Applications of UART:

UART is used in various applications, including but not limited to:

  • Interfacing microcontrollers with sensors, displays, or other peripheral devices.
  • Communication between microcontrollers or embedded systems.
  • Serial communication between computers and peripherals (e.g., serial ports, RS-232).
  • Debugging and logging data in development and testing scenarios.

Overall, UART is a simple yet effective serial communication protocol that remains widely used due to its ease of implementation, flexibility, and compatibility across a broad range of electronic devices and systems.