Troubleshooting & glossary

Symptom-led diagnosis and precise terminology.

15 · REFERENCE

Troubleshooting & glossary

Start from the visible symptom

01

Cannot open RTU port

Close other serial tools, reselect the discovered port, confirm OS permission and adapter presence, then reconnect.

02

Connects but every request times out

Verify Unit ID, serial framing or TCP gateway routing. On RTU, test Unit-ID discovery before scanning addresses.

03

Device returns an exception

Inspect the exception code. Illegal Function points to FC support; Illegal Data Address points to space/range; Illegal Data Value points to quantity or payload.

04

View shows no updates

Confirm the source is running, its Read Plan contains the address, and Health shows completed requests rather than only an open connection.

05

Value is plausible but wrong

Inspect raw words, verify PDU address, width, signedness, byte/word order, then scale and offset—in that order.

06

Trend has no samples

Start every attached source, use numeric/Boolean tags, and ensure the current time window overlaps collected data.

07

Polling becomes slow

Check latency, retries, RTU utilization, oversized ranges, illegal gaps, and whether automation currently owns the connection.

08

Automation cannot run

Check Professional entitlement, active connection profile, validation errors, required parameters/dataset, and read-only status for writes.

Minimal support package

Busloom version, operating system, and transport type.
The exact operation, expected result, and actual result.
Active profile facts with secrets and private infrastructure removed.
A bounded Raw Traffic or Trend session that contains one reproduction.
The project only after reviewing endpoints, notes, and certificate paths.

Glossary

PDU address: Zero-based address carried in the Modbus protocol data unit.
Documentation address: Human-facing notation such as 40001; its base and prefix convention must be confirmed.
Unit ID: Server/slave identifier used on RTU and by many TCP gateways.
Source view: Running acquisition definition that produces raw bits or words.
Tag: Named decoding definition beginning at one address.
Frame: One transmitted or received RTU ADU or TCP ADU shown as protocol evidence.
Session artifact: Read-only saved Trend or Raw Traffic capture that can replay without a device.
Project artifact: Editable .busloom.json configuration used for future work.

STILL BLOCKED?

Send the smallest reproducible device story.

One precise request and its evidence is more useful than an unbounded traffic dump.

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