UART Protocol

UART Protocol Pin Configuration

The Universal Asynchronous Receiver-Transmitter (UART) protocol involves a set of physical pins used for serial communication between devices. These pins handle the transmission and reception of data, as well as provide additional control signals for synchronization and error detection. Here’s a detailed breakdown of the key UART pins and their functions:

Device A	Device B
Tx	Rx
Rx	Tx
GND	GND

1. TX (Transmit) Pin

• Function: The TX pin is used to transmit data from the UART transmitting device (such as a microcontroller or computer) to the UART receiving device.
• Description:
  • The transmitting device sends serial data through the TX pin, which is transmitted one bit at a time.
  • The signal is typically in the form of a logic low (0) or logic high (1), with a start bit marking the beginning of data transmission.
  • The transmitting device drives the TX pin, while the receiving device listens to it on its RX pin.
• Common Pin Names:
  • TXD (Transmit Data)
  • TXD0 (Transmit Data Pin 0)

2. RX (Receive) Pin

• Function: The RX pin is used to receive data sent from the UART transmitting device.
• Description:
  • The receiving device listens to the RX pin for incoming serial data.
  • When data is transmitted from the TX pin of the sending device, it is received on the RX pin of the receiving device, typically in the form of a stream of bits.
  • The signal received on the RX pin is processed by the receiving UART module to reconstruct the original data.
• Common Pin Names:
  • RXD (Receive Data)
  • RXD0 (Receive Data Pin 0)

3. RTS (Request to Send) Pin (Optional)

• Function: The RTS pin is used for hardware flow control to signal that the transmitter is ready to send data.
• Description:
  • When the RTS pin is low (active), it indicates that the transmitting device is ready to send data and is requesting permission to send data to the receiver.
  • The receiving device can assert the CTS (Clear to Send) pin in response to indicate whether it is ready to receive data.
  • If RTS is high, the transmitter indicates that it is not ready to send data, typically because the receiver’s buffer is full.
• Common Pin Names:
  • RTS (Request to Send)
  • RTS0 (Request to Send Pin 0)

4. CTS (Clear to Send) Pin (Optional)

• Function: The CTS pin is used for hardware flow control to signal that the receiver is ready to receive data.
• Description:
  • The CTS pin is an input for the receiving device. When it is low (active), it indicates that the receiver is ready to accept data.
  • If the CTS pin is high, it means the receiver is not ready to receive more data, and the transmitting device should wait.
  • The CTS pin works in conjunction with the RTS pin to enable flow control between devices.
• Common Pin Names:
  • CTS (Clear to Send)
  • CTS0 (Clear to Send Pin 0)

5. DTR (Data Terminal Ready) Pin (Optional)

• Function: The DTR pin is used by the transmitting device to signal that it is ready to communicate and exchange data with the receiving device.
• Description:
  • The DTR pin is usually an output from the data terminal (transmitter) to the data communication equipment (receiver).
  • When DTR is asserted (low), it indicates that the transmitting device is ready for communication.
  • It is often used in conjunction with other control pins to establish the connection.
• Common Pin Names:
  • DTR (Data Terminal Ready)
  • DTR0 (Data Terminal Ready Pin 0)

6. DSR (Data Set Ready) Pin (Optional)

• Function: The DSR pin is used by the receiver to signal that it is ready to receive data from the transmitting device.
• Description:
  • The DSR pin is an input on the receiving device. When it is low, it signals that the receiving device is ready to receive data.
  • If DSR is high, it indicates that the receiver is not ready, and the transmitter should pause data transmission until DSR is asserted.
• Common Pin Names:
  • DSR (Data Set Ready)
  • DSR0 (Data Set Ready Pin 0)

7. RI (Ring Indicator) Pin (Optional)

• Function: The RI pin is used to signal the presence of an incoming call or data connection in some communication systems, especially in modems.
• Description:
  • The RI pin is used in devices like modems to indicate the arrival of a ring signal, often from a telephone line.
  • It is typically used in conjunction with the DTR pin to establish the connection.
• Common Pin Names:
  • RI (Ring Indicator)
  • RI0 (Ring Indicator Pin 0)

8. GND (Ground) Pin

• Function: The GND pin is essential for completing the electrical circuit between devices and ensuring proper signal transmission.
• Description:
  • The GND pin provides the common ground reference for all signals, including TX, RX, and control pins.
  • Proper grounding ensures accurate signal interpretation and helps prevent data corruption due to floating voltage levels.