Timepulse

The u-blox module outputs a configurable pulse signal on GPIO 5. This is typically used as a PPS (Pulse Per Second) signal for time synchronization. On supported HATs, the same signal also drives the LED, so changing the timepulse configuration may also affect the visible blink pattern.

The waveform below starts with an annotated 1 Hz pulse at 10% duty cycle so you can see how polarity decides whether the rising or falling edge lands exactly on the top of the second. The lower examples show the same GPIO 5 output at 5 Hz / 10%, 10 Hz / 50%, and a fix-dependent transition where pulseWhenNoFix uses one waveform until the receiver has a fix and fixedPulse takes over.

If the receiver has no fix, pulseWhenNoFix can emit a different waveform or disable the output entirely. A common pattern is a slower pulse / no pulse before fix and a different period or duty cycle once the receiver is locked.

config.timepulsePinConfig = TimepulsePinConfig {
    .active = true,
    .fixedPulse = { .frequency = 1, .pulseWidth = 0.1f },
    .pulseWhenNoFix = std::nullopt,
    .polarity = ETimepulsePinPolarity::RisingEdgeAtTopOfSecond
};

config.timepulse_pin_config.active = true;
config.timepulse_pin_config.fixed_pulse.frequency = 1;
config.timepulse_pin_config.fixed_pulse.pulse_width = 0.1f;
config.timepulse_pin_config.polarity = JP_GNSS_TIMEPULSE_POLARITY_RISING_EDGE;

config['timepulse_pin_config'] = {
    'active': True,
    'fixed_pulse': { 'frequency': 1, 'pulse_width': 0.1 },
    'pulse_when_no_fix': None,
    'polarity': gnsshat.TimepulsePolarity.RISING_EDGE
}

Note

Kernel PPS Conflict — If you use the kernel PPS driver (dtoverlay=pps-gpio,gpiopin=5) for chrony/gpsd, do not call enableTimepulse() from the library — both use GPIO 5 and cannot coexist.