Barcode Scanner Serial Port Connection (RXD, TXD, VCC, GND) Guide

The serial cable of a barcode scanner contains four critical pins: RXD (Receive Data), TXD (Transmit Data), VCC (Power

Positive), and GND (Ground). Connection strategies must be adjusted according to the target device type:

Connection to PC/Industrial Computer RS232 Port

Cross-connect data lines:

Scanner RXD → Device TXD

Scanner TXD → Device RXD

Connect GND to device GND for common grounding

VCC connection depends on power supply capability:

If the computer port cannot supply power, use an external 3.3V or 5V power source (select according to scanner specifications)

Connection to PLC (RS232 Interface)

Standard RS232 pinout:

Scanner pin 2 (TXD) → PLC pin 3 (RXD)

Scanner pin 3 (RXD) → PLC pin 2 (TXD)

Scanner pin 5 (GND) → PLC pin 5 (GND)

For RS485 interface:

Connect scanner GND to PLC RS485 interface B (D-) pin

Connection to Microcontrollers/Development Boards (e.g., ESP32)

Basic connection:

Scanner TX → Board RX (e.g., ESP32 UART1_RX on GPIO9 - refer to board manual)

GND to board GND

Voltage level considerations:

Add level-shifting module if voltage mismatch exists (e.g., 5V to 3.3V)

Power options:

VCC can be sourced from board's 3.3V power interface (observe current limits)

Or use separate power supply

Important Notes:

Always verify pin definitions in the device manual to prevent faults

Ensure baud rate and protocol settings match between devices

Industrial applications may require additional signal conditioning

(Technical Note: This translation maintains precise technical terminology while adapting connection descriptions to international standards.

Voltage specifications and interface types are preserved with exact values for accurate implementation.)