Troubleshooting Dual RS232 Ports on VCAN1401-Mesh

Troubleshooting Guide: When One RS232 Port Does Not Work on VCAN1401-Mesh

This document summarizes a real case and provides a clear procedure to help customers diagnose why one RS232 port works and the other does not, even when both ports have identical settings.

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1. Problem Description

A customer using the VCAN1401-Mesh radio encountered the following issue:

• The radio has two RS232 ports.
• Only one port works normally.
• The second port outputs only the following message at boot and then stops responding:

▒/EV-INFO start▒▒j
$CFGSYS,h10

• Both ports are configured identically (AT Command mode, 9600 UART).
• On another radio, both ports work correctly, so the customer suspects a hardware issue.

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2. Step 1: Verify UART Settings in Web UI

Navigate to:

Setting-Tool → UART

Confirm the following for both RS232 ports:

• UART mode is set correctly
• Baud rate matches your device
• Protocol (AT command or Data UART) is correctly selected
• No unexpected changes were made

In the customer’s case, both ports were configured properly and matched the settings on the working radio.

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3. Step 2: Provide Parameter Screenshots

If the problem persists, provide:

• Web UI screenshots of both UART ports
• Any wiring photos
• A short video showing the behavior

This helps engineers check for configuration inconsistencies that may not be obvious from text alone.

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4. Step 3: Check Possible Hardware or Wiring Issues

Even if the Web UI settings are correct, the issue may come from:

• Loose or damaged TX, RX, or GND wires
• Wrong pin mapping
• Poor contact in the connector
• Short circuits on the port
• Damaged external serial device

In many cases, the serial wiring is the root cause, not the radio module.

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5. Step 4: Perform a UART Loopback Test (Important)

To confirm whether the RS232 port hardware is functioning, use this method:

(1) Switch the port to normal “Data UART” mode

AT Command mode may block echo responses.

(2) Prepare a loopback

• Short TX and RX together on the cable connected to the problematic port.
• Keep GND connected.

(3) Use a serial terminal

• Open your RS232 terminal on a PC
• Send characters (e.g., “12345”)

(4) Check the result

✔ If characters echo back:

The port hardware is working (TX, RX, and GND lines are good).
The issue is likely external wiring or device connection.

✘ If characters do not echo back:

This strongly indicates:

• Incorrect cable wiring
• Damaged connector
• Short/open circuit on TX/RX
• Hardware failure of the serial port on the radio

This test quickly narrows down whether the issue is internal or external.

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6. Step 5: Report Results to Support

Share:

• Loopback test results
• Photos of wiring
• Any additional observations

This allows engineers to determine the next step: repair, replacement, or further debugging.

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7. Conclusion

When one RS232 port works and the other does not on a VCAN1401-Mesh radio, the issue is typically related to wiring or hardware on the non-working port.

Following these steps—especially the loopback test—helps confirm whether the problem is external wiring or the port hardware itself.