Fix slow OBD value load on dashboard (BUG-19)

BUGS.md

@@ -37,6 +37,22 @@ When CLOSED, move the entire entry to Resolved — don't duplicate.
   - Keep `systemd-timesyncd` for online NTP; fall back to the RTC (DS3231) and optionally
     GNSS time when offline.
 
+### BUG-19 — Dashboard OBD values slow to appear while the car is running
+- **Status**: `OPEN` 2026-08-13
+- **Phase**: 29
+- **Symptom**: on the Pi dashboard, the speed/RPM/coolant/fuel/throttle cards stay on
+  "—" for a long time after the page loads (or after ignition) before populating, even
+  though the car is running and OBD is connected.
+- **Cause**: the value cards were populated **only** by socket.io push events from the
+  OBD polling threads — the dashboard never pulled a current snapshot on load, so a
+  freshly loaded page had to wait for the next poll tick (plus any reconnect/probe
+  latency). `/api/obd/status` only returned the connection state, not the actual
+  values, so there was no REST fallback either.
+- **Fix**: emit a full current-value snapshot on socket connect, and extend
+  `/api/obd/status` to return live speed/RPM/coolant/fuel/throttle/MIL so the dashboard
+  fills the cards immediately on load (and every 15 s) via REST. Needs in-car
+  verification.
+
 ---
 
 ## Resolved

app.py

@@ -203,11 +203,19 @@ def gps_status():
 
 @app.route('/api/obd/status')
 def obd_status():
+    port = app_obd._find_obd_port()
+    connected = app_obd._is_car_connected()
     return jsonify({
-        "adapter_present": bool(app_obd._find_obd_port()),
+        "adapter_present": bool(port),
-        "port": app_obd._find_obd_port(),
+        "port": port,
-        "car_connected": app_obd._is_car_connected(),
+        "car_connected": connected,
-        "status_label": "Connected" if app_obd._is_car_connected() else "Disconnected",
+        "status_label": "Connected" if connected else "Disconnected",
+        "speed": app_obd.get_fresh_speed(),
+        "rpm": app_obd.rpm,
+        "coolant_temp": app_obd.coolant_temp,
+        "fuel_level": app_obd.fuel_level,
+        "throttle_position": app_obd.throttle_position,
+        "mil_on": app_obd.get_fresh_mil(),
     })
 
 @app.route('/api/trip/<int:trip_id>')

modules/app_obd.py

@@ -271,9 +271,51 @@ def get_fresh_speed(max_age=5):
     return speed
 
 
+def emit_current_state():
+    """Push the current OBD values to a newly connected dashboard.
+
+    The polling threads only emit on their next tick, so a freshly loaded
+    page would otherwise sit on "—" until then. Emitting a snapshot here makes
+    the cards fill immediately on connect/reconnect instead of waiting for the
+    next poll cycle (or a reconnect/probe round-trip).
+    """
+    connected = _is_car_connected()
+    app_events.socketio.emit(
+        "obd_status", obd_status[1] if connected else obd_status[0]
+    )
+    if connected:
+        app_events.socketio.emit("obd_speed", get_speedtime())
+        app_events.socketio.emit("obd_rpm", rpm if rpm is not None else "-")
+        app_events.socketio.emit(
+            "obd_coolant_temp",
+            coolant_temp if coolant_temp is not None else "-",
+        )
+        app_events.socketio.emit(
+            "obd_fuel_level",
+            fuel_level if fuel_level is not None else "-",
+        )
+        app_events.socketio.emit(
+            "obd_throttle",
+            throttle_position if throttle_position is not None else "-",
+        )
+        if mil_on is not None:
+            app_events.socketio.emit(
+                "obd_mil", {"on": mil_on, "dtc_count": len(dtc_codes)}
+            )
+        if dtc_codes:
+            app_events.socketio.emit("obd_dtc", dtc_codes)
+    else:
+        app_events.socketio.emit("obd_speed", "-")
+        app_events.socketio.emit("obd_rpm", "-")
+        app_events.socketio.emit("obd_coolant_temp", "-")
+        app_events.socketio.emit("obd_fuel_level", "-")
+        app_events.socketio.emit("obd_throttle", "-")
+
+
 def obd_connection():
     """Emit current state for a newly connected browser and ensure OBD is running."""
     start_obd()
+    emit_current_state()
 
 
 def _persist_car_connected():

static/js/yaris.js

@@ -314,9 +314,26 @@ async function refreshObdStatus() {
         if (el) el.textContent = status.adapter_present
             ? (status.car_connected ? 'Connected' : 'Adapter only')
             : 'Not detected';
+
+        // Fill the value cards from the REST snapshot so they appear immediately
+        // on load, even if the socket connection is slow to establish. Socket
+        // events keep updating them live afterward.
+        if (status.car_connected) {
+            fillObdValueCard('obd-speed', status.speed, 'km/h');
+            fillObdValueCard('obd-rpm', status.rpm, 'rpm');
+            fillObdValueCard('obd-coolant', status.coolant_temp, '°C');
+            fillObdValueCard('obd-fuel', status.fuel_level, '%');
+            fillObdValueCard('obd-throttle', status.throttle_position, '%');
+        }
     } catch (e) {
         // Socket events will eventually update it
     }
 }
+
+function fillObdValueCard(id, value, unit) {
+    if (value == null) return;
+    const el = document.getElementById(id);
+    if (el) el.textContent = value + ' ' + unit;
+}
 refreshObdStatus();
 window.setInterval(refreshObdStatus, 15000);

tests/test_app_obd.py

@@ -72,5 +72,59 @@ class ClearDtcCodesTest(unittest.TestCase):
         mock_mark.assert_called_once()
 
 
+class EmitCurrentStateTest(unittest.TestCase):
+    def setUp(self):
+        self._saved = {
+            name: getattr(app_obd, name)
+            for name in (
+                "speed", "rpm", "coolant_temp", "fuel_level",
+                "throttle_position", "mil_on", "dtc_codes",
+            )
+        }
+
+    def tearDown(self):
+        for name, value in self._saved.items():
+            setattr(app_obd, name, value)
+
+    def _emitted(self, mock_emit):
+        return {call.args[0]: call.args[1] for call in mock_emit.call_args_list}
+
+    def test_connected_emits_current_values(self):
+        app_obd.speed = 42.5
+        app_obd.rpm = 1200
+        app_obd.coolant_temp = 88.0
+        app_obd.fuel_level = 60.0
+        app_obd.throttle_position = 12.0
+        app_obd.mil_on = False
+        app_obd.dtc_codes = []
+        with patch.object(app_obd, "_is_car_connected", return_value=True), \
+             patch("modules.app_events.socketio.emit") as mock_emit:
+            app_obd.emit_current_state()
+        emitted = self._emitted(mock_emit)
+        self.assertEqual(emitted["obd_status"], "Connected")
+        self.assertEqual(emitted["obd_rpm"], 1200)
+        self.assertEqual(emitted["obd_coolant_temp"], 88.0)
+        self.assertEqual(emitted["obd_fuel_level"], 60.0)
+        self.assertEqual(emitted["obd_throttle"], 12.0)
+        # speed is emitted as [time, speed]
+        self.assertEqual(emitted["obd_speed"][1], 42.5)
+
+    def test_disconnected_emits_dashes(self):
+        app_obd.rpm = None
+        app_obd.coolant_temp = None
+        app_obd.fuel_level = None
+        app_obd.throttle_position = None
+        with patch.object(app_obd, "_is_car_connected", return_value=False), \
+             patch("modules.app_events.socketio.emit") as mock_emit:
+            app_obd.emit_current_state()
+        emitted = self._emitted(mock_emit)
+        self.assertEqual(emitted["obd_status"], "Disconnected")
+        self.assertEqual(emitted["obd_speed"], "-")
+        self.assertEqual(emitted["obd_rpm"], "-")
+        self.assertEqual(emitted["obd_coolant_temp"], "-")
+        self.assertEqual(emitted["obd_fuel_level"], "-")
+        self.assertEqual(emitted["obd_throttle"], "-")
+
+
 if __name__ == "__main__":
     unittest.main()