BHARAT TEST SUITE by Raju Bros Softech Pvt ltd

Learning Centre · Serial troubleshooting

Recover a changed
Windows COM port.

A saved COM number can change when a serial adapter reconnects. BHARAT TEST SUITE can use captured USB identity to locate the device, but the strength and uniqueness of that identity determine how reliable the match is.

Read the SCPI query guide
/01

Identify the connection problem

Reviewed 15 October 2026 · Raju Bros Softech Pvt ltd · Based on documented application behavior; validate your station.

  • Stop production and leave the fixture in its approved safe state before reconnecting or rebinding an adapter.
  • Use an authorised configuration account to change device settings. Record the saved device name, old COM number and current Windows port before editing.
  • Confirm Windows detects the intended physical adapter. Check power, cable and its vendor driver if no COM port appears.
Example scenario. An adapter previously appeared as COM3 and now appears as COM7. These numbers illustrate a Windows reassignment; they are not required settings. Identify the physical adapter before changing the saved device.
/02

Refresh, identify and save

  1. Open the existing device

    In Device Configuration, select the saved serial device. Use REFRESH COM PORTS and select the intended connected adapter; do not create a second record just because its port number changed.

  2. Inspect the captured identity

    Review VID, PID, USB Serial Number, USB Instance ID, USB Location Path, Container ID, Hardware ID and Friendly Name where available. Prefer a genuine unique serial number. If the status is LOCATION LOCKED, keep the adapter on the same physical USB port.

  3. Review automatic detection status

    Check Auto Detect By USB ID and the Auto Detect Safety message. The application can disable auto-detection when duplicate identities are found during save. Read the resulting warning; do not assume the checkbox stayed enabled.

  4. Save and verify the actual device

    Use TEST CONNECTION to inspect the detected COM port and match explanation, then SAVE DEVICE. Recheck the saved Auto Detect status. Run the instrument’s supported read-only identification query from Maintenance to confirm the physical device.

  5. Check reconnection during commissioning

    When it is safe to do so, reconnect the adapter under your station procedure and repeat the detection and identification checks. Record the result before returning the station to production.

Device configuration Inside the software
Actual application capture · COM / Serial setup for a new device, before instrument details are entered.
/03

How the application chooses a port

With Auto Detect By USB ID enabled, the current implementation checks the following identity matches in order. A unique match can be selected at each stage.

Order Match
1 VID + PID + USB serial number
2–5 VID + PID with USB instance ID, USB location path, container ID, then hardware ID
6 Friendly name
7 A currently unique VID/PID pair
Fallback Saved COM Port, then Last Known COM Port, then runtime Current COM Port, when no blocking ambiguity remains

If multiple devices remain ambiguous, detection returns an error instead of choosing a fallback port. With automatic detection disabled, the saved-port path is used. Friendly-name, VID/PID-only and COM-number matches are weaker evidence than a unique serial number: confirm instrument identity after a reconnect.

/04

Resolve duplicate-adapter warnings

Duplicate USB identity

Two adapters may share VID/PID or even the reported serial identity. Saving can disable Auto Detect for affected devices and use fixed COM settings. Read the warning and verify each physical connection deliberately.

Location-bound adapter

An adapter without a usable unique serial may rely on USB location or instance identity. Moving it to another USB socket or hub can invalidate that binding. Reselect and save only after identifying the intended adapter.

Stronger replacement identity

For a station that depends on automatic reconnection, choose hardware with a verified unique USB serial number. Recommission its saved binding and read-only query before production use.

/05

Troubleshooting and expected evidence

Observed result Next action
Not found by USB identity or fallback COM port Check physical connection and driver, refresh the list, and compare the captured identity with the saved record.
Multiple COM devices match Identify each adapter, inspect duplicate warnings and avoid guessing from VID/PID alone. Review unique-serial hardware or a deliberate fixed-port arrangement.
Detected port, but a query times out Port recovery succeeded only at detection level. Check the instrument address, serial parameters, protocol and framing using the SCPI guide.
Auto Detect disabled after saving Read the duplicate-identity warning. Record the fixed COM mapping and validate it; do not treat this state as automatic recovery.
Will USB auto-detection always survive moving to a different socket?

No. A unique USB serial number is stronger than a location-based identity. A location-locked adapter must remain on its expected USB port or be deliberately rebound and checked.

Why should I check the reply after the COM device is found?

Port detection establishes a connection identity match. A supported query helps confirm that the intended instrument is behind that adapter before any state-changing operation.

Connect and check a SCPI instrument ↗ Documentation and support ↗

Need help with your test station?

Share your instruments, intended workflow and the question you need to resolve.

Discuss your station

BHARAT TEST SUITE · Application screen