PPS Source (Non-GPS)

A non-GPS PPS Source, such as a radio, may also be used for clock timing. It cannot be used for synchronization since there is no time data, but it can be used to ensure a clock ticks accurately.

To configure a Non-GPS PPS source:

  • Navigate to Services > NTP

  • Click the PPS tab

  • Configure the settings as follows:

    Serial Port

    All serial ports detected on the firewall are listed. Select the port with the GPS attached. On-board hardware serial ports start with cuau, USB serial ports are prefixed with cuaU.

    Fudge Time 1

    Specifies a constant to be added to the PPS signal as an offset, to account for delay between the transmitter and receiver.

    Stratum

    Used to configure the stratum of the PPS source. The default value is 0 so the PPS source is preferred over all others. If another clock must be preferred instead, set the stratum value higher than the stratum of the preferred clock.

    Flags
    Falling edge PPS signal processing

    When set, the falling edge of the PPS signal is used for timing, rather than the rising edge.

    Kernel PPS clock discipline

    When set, the OS Kernel will use PPS directly for timing.

    Record a timestamp

    Record a timestamp once for each second, which is useful for constructing Allan deviation plots.

    Clock ID

    A 1-4 character identifier used to change the PPS Clock ID. The default value is PPS.

  • Click Save