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 r

eception 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.