[Jeff Geerling] has been adhering to the several open up source time tasks for some time now, and is at last capable to reveal a doing work and reasonably priced answer for nanoseconds-exact timekeeping in your regional lab. The risk of a very low-value time server came about with the introduction of the Raspberry Pi CM4 compute module back in Oct 2020, whose Broadcom network chip (BCM54210PE) supports PTP (Precision Time Protocol, IEEE-1588) 1PPS output and components-dependent time stamping. Irrespective of the CM4 knowledge sheet specifying PTP assist, it was not out there in the kernel. An concern was elevated in Feb last yr, and Raspberry Pi kernel assistance was eventually released this thirty day period.
[Jeff] demonstrates how effortless it is to get two CM4 modules to synchronize to in just a handful of tens of nanoseconds in the video underneath the break. That by itself can be extremely valuable on quite a few assignments. But if you want really steady and absolute time, you have to have a stratum 1 external source. These time servers, referred to as grandmasters in PTP nomenclature, have usually been specialised pieces of package costing tens of countless numbers of bucks, working with precision oscillators for security and RF indicators from stratum units like navigation satellites or terrestrial broadcast stations to get complete time. But as Lasse Johnsen, who worked on the kernel updates remarks in the online video:
In 2022 these purpose-built grandmaster clocks from the conventional sellers are about as relevant as the equipment internet servers like the Raq and Qube have been back again in 1998.
It is now attainable to create your personal low-price tag stratum 1 time server in your lab from open resource jobs. Two examples revealed in the video. The Open Time Server project’s Timecard utilizes a GNSS satellite receiver and a Microchip MAC-SA5X Rubidium oscillator. If which is overkill for your jobs or budget, the Time4Pi CM4 hat is about to be launch for beneath $200. If precise time preserving is your thing, the technologies is now within achieve of the regular property lab. You can also insert PTP to a non-CM4 Raspberry Pi — check out the Actual-Time HAT that we protected last 12 months.