Step 1: UART, Baud Rate and Polling Mechanism

UART is a hardware communication protocol used for asynchronous serial data transmission between devices without a shared clock signal.

UART communication typically uses TX (transmit) and RX (receive) lines and sends data in the form of frames consisting of a start bit, data bits, optional parity bit, and stop bit. A commonly used configuration is 8N1, which means eigh data bits, no parity bit, and one stop bit.

UART is widely used in embedded systems for debugging, data logging, and communication with external devices due to its simplicity and reliability.

Proper UART operation requires correct configuration of baud rate, data bits, parity, and stop bits on both communicating devices.

Baud rate is the speed at which data is transmitted over a serial communication channel, measured in bits per second (bps). For example, a baud rate of 9600 bps means 9600 bits are transferred every second.

Both the transmitter and receiver must be configured with the same baud rate. A mismatch in baud rates will result in incorrect or unreadable data during communication.

Baud rate directly affects communication reliability and timing. Lower baud rates are generally more reliable over longer distances, while higher baud rates allow faster data transfer but require more accurate clock configuration.

In microcontrollers, the baud rate is generated by dividing the system clock using a baud rate generator register, making correct clock and register configuration essential for successful UART communication.

Polling is a technique in which the microcontroller repeatedly checks the status of a peripheral register to determine whether an event has occurred, such as receiving or transmitting data.

In UART polling mode, the CPU waits until a specific status flag (for example, transmit buffer empty or receive data available) is set before performing the corresponding operation.

Polling is simple to implement and easy to understand, making it suitable for small or low‑complexity applications, but it can be inefficient because the CPU remains busy checking flags instead of performing other tasks.