Time

Boreas is designed to provide an accurate time reference via an internal oscillator.

The oscillator is a temperature compensated disciplined oscillator.

For a device with a GNSS receiver, when a GNSS fix is available, the internal oscillator uses GNSS time to precisely correct itself to within the accuracy specified for the GNSS receiver.

When a GNSS fix is lost, time accuracy will slowly drift.

The time can be accessed via the following means:

• A dedicated 1PPS Signal. This is the preferred means to obtaining the most accurate timing output.

• A 1PPS output over GPIO or the Auxiliary port, see 1PPS Output of the Dynamic Pin Functions.

• A built-in Precision Time Protocol (PTP) version 2 server for synchronisation with network-connected devices which require high accuracy time. The PTP server broadcasts PTP messages (Sync, Follow Up, Announce) to multicast IP address 224.0.1.129. The PTP broadcasts are sent whenever an Ethernet connection is established and cannot be disabled.
  
  - PTP version: 2, generic profile
  - Master output: UDP multicast
  - Clock sync: 2-step (1-step used as fallback if necessary)
  - 1PPS output: Internal clock / GNSS
  - Protocol: IEEE 1588
  - Delay mechanism: E2E (delay request-response)

• A built-in Network Time Protocol (NTP) server:

  • The NTP message will be broadcast on the IP address of the device, on UDP port 123.

Note: The time filter will need to be initialised before the device will start sending NTP or PTP messages.