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Check the HMI RS232/485/422 port COM with a loopback test on RX and TX pins
What is a loopback test
A loopback test involves sending and receiving data from a single COM port. A signal is sent by a device and returns to it after traversing part or all of a network.
This is a primary method to troubleshoot serial communication issues and ensure that a COM port is functioning properly.
The loopback test provides information about:
- problems present on a network of serial devices
- the existing means to determine if a peripheral is functioning correctly
How to Perform a Loopback Test
- RS-232: Connecting the transmit pin 3 (TX) to the receive pin 2 (RX)
- RS-422 and RS-485: Connect TX+ pin to RX+ and TX- to RX-
Wirring of the HMI serial port
HMI D-sub 9 pins 1 2 3 4 5 6 7 8 9 View from outside |
RS232, RS485 and RS422 pins |
HMI-Tool test project
Download the project for testing
Wirring issue
If you don’t see this indicator light blinking on your HMI, it’s probably a wiring cable problem. |