Fix pps clock when not connected to gps

lib/car_os/system_clock.py

@@ -0,0 +1,47 @@
+import time
+
+class SystemClock:
+    def __init__(self):
+        self._update_time_ns = time.monotonic_ns()
+        self._time = (0, 0, 0, 0)
+        self._previous_timestamp = 0
+        self._previous_utc_h = 0
+
+    def update(self):
+        self._update_time()
+        current_timestamp = self.utc_timestamp
+        if self._previous_utc_h == 23 and self.utc_time[0] == 0:
+            current_timestamp += 86400
+        delta = current_timestamp - self._previous_timestamp
+        self._previous_timestamp = current_timestamp
+        self._previous_utc_h = self.utc_time[0]
+        return delta
+
+    def _update_time(self):
+        current_time = time.monotonic_ns()
+        time_diff = current_time - self._update_time_ns
+        self._update_time_ns = current_time
+        s, ns = divmod(self._time[3]+time_diff, 1e9)
+        m, s = divmod(self._time[2]+s, 60)
+        h, m = divmod(self._time[1]+m, 60)
+        _, h = divmod(self._time[0]+h, 24)
+        self._time = (h, m, s, ns)
+
+    def update_from_pps_clock(self, pps_time, pps_ref_monotonic):
+        self._time = pps_time[:]
+        self._update_time_ns = pps_ref_monotonic
+        self._update_time()
+        self._previous_timestamp = self.utc_timestamp
+
+    @property
+    def utc_time(self):
+        self._update_time()
+        return self._time
+
+    @property
+    def utc_timestamp(self):
+        return self._time[0] * 3600 + self._time[1] * 60 + self._time[2] + (self._time[3] / 1_000_000_000)
+
+    @property
+    def update_time_ns(self):
+        return self._update_time_ns