Problem Description
A PEAK PLIN-USB interface (IPEH-004052) running PLIN-View Pro 3.2.0.174 transmits correct frames in Publisher mode — the oscilloscope shows the expected frame values. In Subscriber mode, however, the transmitted frame ID (0x15) appears on the oscilloscope as a meaningless multi-byte value (0x3F635547). The LIN slave and the PLIN hardware are powered from the same 12 V supply, so a missing supply or ground offset between the nodes is not the cause.
Root Cause
This is expected bus behavior, not a PLIN-View Pro bug. In Subscriber mode the master only sends the frame header — break field, sync field (0x55), and the protected identifier — and then releases the bus for the slave to append the response data bytes. When no slave answers, the oscilloscope captures only that raw header sequence and any protocol-agnostic decode of the waveform renders it as a long nonsense number instead of the clean ID 0x15. The correct frame value seen in Publisher mode confirms the PLIN hardware, cabling, and PLIN-View Pro configuration are working; the fault is the missing slave response.
Diagnostic Procedure
- Confirm the observed waveform contains the break field, the sync byte 0x55, and the protected identifier — this matches the reported scope capture and confirms the master side is transmitting correctly.
- Inspect the LIN slave device: verify it is running, configured to respond to the requested frame ID, and connected to the same LIN bus line and ground.
- Re-capture the bus after fixing the slave. A working exchange shows the master header immediately followed by the slave's data bytes and checksum on the same frame.
Because Publisher mode already produces a correct frame on the scope, do not spend time changing PLIN-View Pro settings or swapping the PLIN-USB hardware; direct all troubleshooting effort at the slave side.
Verification
The issue is resolved when the oscilloscope shows a complete frame: break, sync (0x55), protected identifier matching the requested ID, followed by the slave's response bytes. If the header still appears alone with no response bytes, the slave remains the fault — check its firmware state, its LIN configuration, and its physical connection to the bus.
FAQ
Why does my LIN frame ID show as garbage on the oscilloscope in Subscriber mode?
Because the slave never responded. The scope is showing the raw master header — break field, sync field 0x55, and protected identifier — decoded as one meaningless number instead of the sent ID.
Does PLIN-View Pro support sending subscriber frames?
Yes. Sending subscriber frames with PLIN-View Pro is fully supported; a correct Publisher-mode capture on the same setup confirms the software and PLIN-USB hardware are not the problem.
What should I check when a LIN master header gets no slave response?
Check the slave device: confirm it is powered, running, wired to the same LIN line and ground, and configured to answer the requested frame ID. A valid frame shows the slave's data bytes immediately after the header.