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[Jeff Geerling] has been adhering to the various open up supply time assignments for some time now, and is last but not least able to demonstrate a working and cost-effective remedy for nanoseconds-correct timekeeping in your neighborhood lab. The chance of a very low-price tag time server came about with the introduction of the Raspberry Pi CM4 compute module back again in Oct 2020, whose Broadcom community chip (BCM54210PE) supports PTP (Precision Time Protocol, IEEE-1588) 1PPS output and hardware-dependent time stamping. Even with the CM4 details sheet specifying PTP guidance, it wasn’t obtainable in the kernel. An challenge was elevated in Feb very last yr, and Raspberry Pi kernel aid was ultimately produced this month.
[Jeff] demonstrates how straightforward it is to get two CM4 modules to synchronize to within just a number of tens of nanoseconds in the online video below the break. That alone can be very valuable on numerous initiatives. But if you want definitely secure and complete time, you will need a stratum 1 exterior resource. These time servers, named grandmasters in PTP nomenclature, have historically been specialized pieces of kit costing tens of hundreds of dollars, utilizing precision oscillators for security and RF signals from stratum gadgets like navigation satellites or terrestrial broadcast stations to get absolute time. But as Lasse Johnsen, who worked on the kernel updates remarks in the movie:
In 2022 these reason-created grandmaster clocks from the common suppliers are about as suitable as the appliance internet servers like the Raq and Qube were being back in 1998.
It is now achievable to make your own very low-value stratum 1 time server in your lab from open up resource jobs. Two illustrations revealed in the movie. The Open Time Server project’s Timecard employs a GNSS satellite receiver and a Microchip MAC-SA5X Rubidium oscillator. If that’s overkill for your tasks or finances, the Time4Pi CM4 hat is about to be launch for below $200. If accurate time holding is your detail, the engineering is now inside of access of the normal household lab. You can also include PTP to a non-CM4 Raspberry Pi — examine out the Actual-Time HAT that we lined previous yr.
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