Software & Communication Architecture

# Model layer — runs entirely on a worker QThread.
# Never touches a Qt signal: it just parks the newest reading behind a lock.
class OBDModel(QThread):
    def __init__(self, port="/dev/ttyUSB0"):
        super().__init__()
        self._lock = threading.Lock()
        self._latest = Telemetry()
        self._running = True

    def snapshot(self):
        """Thread-safe read, called from the GUI thread's timer."""
        with self._lock:
            return self._latest

    def run(self):
        connection = obd.OBD(self.port, fast=False)
        while self._running:
            snapshot = Telemetry(
                rpm=self._query(connection, obd.commands.RPM),
                coolant_c=self._query(connection, obd.commands.COOLANT_TEMP),
                speed_kmh=self._query(connection, obd.commands.SPEED),
            )
            with self._lock:
                self._latest = snapshot  # publish only — no signal here
            time.sleep(0.05)  # 20 Hz poll rate


# Controller layer — GUI-thread QTimer samples the snapshot at 30 Hz.
# This is the ONLY place a pyqtSignal is ever emitted.
class DashboardController(QObject):
    rpm_changed = pyqtSignal(object)

    def _poll(self):
        telemetry = self._model.snapshot()
        self.rpm_changed.emit(telemetry.rpm)