The polling thread owns the ELM327, so reading/clearing trouble codes from
the GUI thread would race PID reads and corrupt the stream. Add a one-off
command path that serializes ad-hoc link work onto the polling thread.
obdcore/scheduler.py:
- PollScheduler.run_oneoff(fn, timeout) enqueues a callable (queue.Queue +
threading.Event) and blocks for its result, re-raising the callable's
exception. tick() drains queued one-offs at its very top, so they run on
the same thread that does PID reads -- never concurrently. When the
scheduler thread isn't running, the job is drained inline on the caller
(still serialized vs tick(), safe because nothing else touches the link).
gui/controller.py:
- Controller.read_dtcs() -> {"stored","pending","permanent"} (modes 03/07/0A,
svc 0x43/0x47/0x4A) and clear_dtcs() -> bool. Both route through the
scheduler one-off when a scheduler exists, else call the link directly.
gui/main.py:
- Diagnostics menu (Read Codes / Clear Codes...) and a right-side QDockWidget
listing codes grouped Stored/Pending/Permanent. Each row is code +
description + system from DtcDatabase; no_start codes are flagged bold red.
- Clear is guarded by a confirmation warning (erases codes + freeze frame;
honest "the code comes right back" / permanent-codes-won't-clear tone from
run_clear in obd_reader.py). On confirm: clear, then re-read immediately and
show whatever returned, reporting active faults that came straight back.
tests/test_diagnostics.py:
- one-off returns its value, re-raises exceptions, is drained before a tick's
PID reads, and runs on a live background thread while polling continues.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016yT89n4zR4qbrySoSiEyZs
Foundation for the PySide6 + pyqtgraph Windows GUI, shared with the terminal
tool. Pure data/IO -- no Qt, no curses.
obdcore/
link.py ElmLink -- ELM327 serial (Mode-01/22, ATRV, DTC read/clear)
mock.py MockLink -- synthetic crank for tests + GUI dev (no truck)
registry.py PidRegistry (verified Ford 6.0 PIDs + confidence) + DtcDatabase
scheduler.py PollScheduler -- prioritized round-robin polling, dead-PID park,
derived channels; tick() is fake-clock test-drivable
store.py TimeSeriesStore (ring buffers + min/max) + CsvRecorder/replay
Design centers on the ELM327 bandwidth limit (~7-15 reads/sec): the active
view subscribes PIDs at chosen rates; acquisition runs off the UI thread;
the GUI only reads the store. FICM_M (09D0) promoted to verified after the
2026-06-30 on-truck crank read (48.0V, intermittent).
tests/test_obdcore.py: decoders vs real truck bytes, crank ramp + peak,
derived BOOST, dead-PID park/revive, record/replay roundtrip -- all pass.
ARCHITECTURE.md: layers, data model, GUI plan, 6.0 stock-PID limits
(no EGT/oil-PSI), feature backlog, P0-P5 roadmap.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016yT89n4zR4qbrySoSiEyZs
justin