Usart/uart

USART stands for Universal Synchronous and Asynchronous Receiver and Transmitter. It is a serial communication protocol that can operate in both synchronous and asynchronous (UART) modes, allowing it to be used for a wide range of communication purposes. In USART communication, data is transmitted one bit at a time over a single communication line or bus. USART is commonly used in microcontroller applications to communicate with other devices such as computers, modems, and other microcontrollers.

USART and UART are communication protocols commonly used in microcontrollers and other devices to facilitate serial communication between devices.

UART (Universal Asynchronous Receiver/Transmitter) is a simple and basic protocol used for asynchronous communication between two devices, typically a microcontroller and a computer or another microcontroller. It provides a means of transmitting and receiving serial data.

USART (Universal Synchronous Asynchronous Receiver/Transmitter) is an expanded version of the UART protocol, offering both synchronous and asynchronous communication. In addition to the basic functionality of the UART, USART provides the option to use a synchronous communication mode, where the clock signal is used to synchronize data transfer between the devices.

Both UART and USART are widely used in various applications, such as RS-232 communication, RS-485 communication, and IrDA (Infrared Data Association) communication, among others.

The wiring diagram for USART (Universal Synchronous Asynchronous Receiver Transmitter) communication depends on the microcontroller and the device it is communicating with. However, here is a general diagram that shows how USART communication is typically set up:

1. Microcontroller USART TX (Transmit) pin connects to the RX (Receive) pin of the device.

2. Microcontroller USART RX (Receive) pin connects to the TX (Transmit) pin of the device.

3. The ground pins of both the microcontroller and the device are connected.

4. Optionally, a common voltage level between the devices can be established with a VCC connection.

It's important to note that some microcontrollers have multiple USART modules and each may have different pin configurations. It's always good to refer to the datasheet of the specific microcontroller to get the correct pinout information.

The circuit diagram for USART (Universal Synchronous Asynchronous Receiver Transmitter) communication is typically composed of the microcontroller and the device it is communicating with. Here's a simple example that shows the basic components involved in USART communication:

1. Microcontroller with a USART module: This is the main component that initiates and manages communication.

2. Transmitter section: This part of the microcontroller sends data to the device. It includes a USART transmitter buffer, a shifter, and a driver circuit to convert parallel data into serial data.

3. Receiver section: This part of the microcontroller receives data from the device. It includes a USART receiver buffer and a serial-to-parallel converter.

4. Serial device: This is the device that the microcontroller communicates with. It could be a computer, a modem, or any other device that has USART communication capabilities.

5. MAX232 or similar level shifter IC: This is an optional component that is used to convert the voltage levels of the USART signals to be compatible with the voltage levels of the serial device.

Note that the specific circuit diagram of USART may vary depending on the microcontroller and the device being used. It is always recommended to refer to the datasheet of the specific components for more information.

A Timing Diagram of USART (Universal Synchronous Asynchronous Receiver Transmitter) displays the sequence of events and the relative timing between the events that occur during the transmission and reception of data using the USART communication protocol.

It typically shows the following signals:

• Transmit Data (TXD): data being transmitted from the USART.

• Receive Data (RXD): data being received by the USART.

• Transmit Clock (TCLK): a clock signal used to time the transmission of data.

• Receive Clock (RCLK): a clock signal used to time the reception of data.

• Start Bit: the first bit transmitted in each data frame, signalling the beginning of a new data word.

• Stop Bit: the last bit transmitted in each data frame, signalling the end of a data word.

• Parity Bit (optional): a bit added for error detection purposes.

Each of these signals has a specific timing related to each other, as defined by the USART protocol being used. The timing diagram shows these relationships and helps to understand the operation of USART communication.

A timing diagram of UART (Universal Asynchronous Receiver Transmitter) displays the sequence of events and the relative timing between the events that occur during the transmission and reception of data using the UART communication protocol.

It typically shows the following signals:

• Transmit Data (TXD): data being transmitted from the UART.

• Receive Data (RXD): data being received by the UART.

• Start Bit: the first bit transmitted in each data frame, signalling the beginning of a new data word.

• Stop Bit: the last bit transmitted in each data frame, signalling the end of a data word.

• Parity Bit (optional): a bit added for error detection purposes.

In UART communication, the transmitting and receiving devices operate at different clock frequencies, and the data is transmitted and received asynchronously, meaning that the transmitting and receiving clocks are not synchronized. This allows for flexible communication between devices with different clock speeds.

The timing diagram shows the relative timing between the data, start and stop bits, and any optional parity bit, helping to understand the operation of UART communication.

#include <avr/io.h>

void UART_init(unsigned int baud)
{
    unsigned int baud_prescaler = (((F_CPU / (baud * 16UL))) - 1);

    // Set baud rate
    UBRR0H = (unsigned char) (baud_prescaler>>8);
    UBRR0L = (unsigned char) baud_prescaler;

    // Enable receiver and transmitter
    UCSR0B = (1<<RXEN0)|(1<<TXEN0);

    // Set frame format: 8 data bits, 1 stop bit
    UCSR0C = (3<<UCSZ00);
}

void UART_transmit(unsigned char data)
{
    // Wait for empty transmit buffer
    while (!(UCSR0A & (1<<UDRE0)));

    // Put data into buffer, sends the data
    UDR0 = data;
}

unsigned char UART_receive(void)
{
    // Wait for data to be received
    while (!(UCSR0A & (1<<RXC0)));

    // Get and return received data from buffer
    return UDR0;
}

void UART_send_string(char *string)
{
    while(*string)
    {
        UART_transmit(*string++);
    }
}

In this code, UART_init the function is used to initialize the UART communication with the specified baud rate. The UART_transmit function is used to transmit a single character, while the UART_receive function is used to receive a single character. The UART_send_string the function is used to transmit a string of characters. The code uses registers specific to the ATmega328P microcontroller, but similar registers exist for other microcontrollers and can be used similarly.

Applications of UART and USART:

1. UART is used in many applications such as personal computers, GPS systems, and Bluetooth devices.

2. USART is commonly used in embedded systems, microcontrollers, and other communication devices to facilitate communication between devices.

Merits of UART:

1. UART is simple to implement and does not require a synchronized clock between the transmitting and receiving devices.

2. UART supports asynchronous communication, which makes it possible to connect devices with different clock speeds.

3. UART is commonly used for low data rate communication, making it ideal for many applications where low data rates are sufficient.

Demerits of UART:

1. UART has a limited data transfer rate compared to other communication protocols.

2. UART has limited error detection and correction capabilities, making it susceptible to data errors.

Merits of USART:

1. USART provides higher data transfer rates compared to UART.

2. USART supports both asynchronous and synchronous communication modes, providing greater flexibility.

3. USART has built-in error detection and correction capabilities, providing more reliable communication.

Demerits of USART:

1. USART requires a synchronized clock between the transmitting and receiving devices, which makes it less flexible than UART.

2. USART is more complex to implement compared to UART, which makes it less suitable for low-cost applications.

In conclusion, UART and USART are both important communication protocols with their advantages and disadvantages. The choice between UART and USART will depend on the specific requirements of the application, such as data transfer rate, error detection and correction capabilities, and cost.