car-os-sensor/lib/car_os/pps.py

import digitalio
import time

    
class PPS:
    def __init__(self, pin):
        self.pin = pin
        self.gpio = digitalio.DigitalInOut(self.pin)
        self.gpio.direction = digitalio.Direction.INPUT
        self.previous_value = self.gpio.value
        self.current_value = self.gpio.value
        self._update_time = time.monotonic_ns()
        self.gps_set = False
        self._pps_offset = [0, 0, 0, 0]
        self._utc = [0, 0, 0]
        self._previous_timestamp = 0
        self._previous_utc_h = 0
        
    def update(self):
        current_time = time.monotonic_ns()
        self.current_value = self.gpio.value
        if not self.current_value and self.previous_value:
            self._update_time = current_time
            self._pps_offset = [0, 0, 0, 0]
            self._utc[2] = self._utc[2] + 1
        self.previous_value = self.current_value
        current_timestamp = self.utc_timestamp
        if self._previous_utc_h == 23 and self.utc[0] == 0:
            current_timestamp += 86400
        delta = current_timestamp - self._previous_timestamp
        self._previous_timestamp = current_timestamp
        self._previous_utc_h = self.utc[0]
        return max(0, delta)
    
    def update_from_gps(self, gps):
        self._utc[0] = gps.time[0]
        self._utc[1] = gps.time[1]
        self._utc[2] = gps.time[2]
        gps.time_updated = False
    
    def on_gps_fixed(self):
        self.gps_set = True
    
    def update_pps_offset(self):
        ns = time.monotonic_ns() - self._update_time
        s, ns = divmod(ns, 1_000_000_000)
        m, s = divmod(self._pps_offset[2] + s, 60)
        h, m = divmod(self._pps_offset[1] + m, 60)
        _, h = divmod(self._pps_offset[0] + h, 24)
        self._pps_offset = [h, m, s, ns]
    
    @property
    def utc(self):
        self.update_pps_offset()
        m, s = divmod(self._pps_offset[2] + self._utc[2], 60)
        h, m = divmod(self._pps_offset[1] + self._utc[1] + m, 60)
        _, h = divmod(self._pps_offset[0] + self._utc[0] + h, 24)
        return (h, m, s, self._pps_offset[3])
    
    @property
    def utc_timestamp(self):
        return self.utc[0] * 3600 + self.utc[1] * 60 + self.utc[2] + (self.utc[3] / 1_000_000_000)