SatPulse

SatPulse is an open source program which makes it easy to run a time server for your local network that enables much more precise synchronization than is possible in a typical NTP-based setup. It runs only on Linux.

A typical NTP stratum-1 server, running on, for example, a Raspberry Pi, connects the PPS (pulse-per-second) output of a GPS receiver to a GPIO or a serial port pin. SatPulse is designed to work with PTP (Precision Time Protocol) and requires a different hardware setup, where the PPS output of the GPS is connected to a PPS input pin on the ethernet controller. The precision comes from taking advantage of the hardware support for PTP in the ethernet controllers on both the server and the client. For more details, please read the Introduction.

There are only a few suitable ethernet controllers with a PPS input pin available at low cost. One notable example is the ethernet controller included in the Raspberry Pi Compute Module 4 and 5, when combined with a IO board that exposes the SYNC_OUT pin. Note that the Raspberry Pi 4 and 5 do not have this capability. For more on supported hardware, please see the Hardware page. It is possible to buy all the necessary hardware for less than $150.

SatPulse does not by itself provide a complete time server: rather it is designed to combine with the PTP (Precision Time Protocol) server provided by the LinuxPTP project, which is called ptp4l. It can also connect to the NTP server provided by the chrony project. This enables a time server that supports both NTP and PTP.

Once you have the necessary hardware see the Quick-start guide, to get started.

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