I’ve wanted to build a low-cost open source Linux system that could function as a PTP grandmaster for a while now. This should be pretty doable with

FriendlyElec NanoPi R5S as PTP Grandmaster Clock with GNSS/GPS Discipline

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2024-10-13 22:30:09

I’ve wanted to build a low-cost open source Linux system that could function as a PTP grandmaster for a while now. This should be pretty doable with IEEE 1588 readily available (if you know where to look) and low-cost GPS receivers with reasonable quality 1PPS outputs.

One of the most compelling features of the NanoPi R5S is that it’s easy to buy from many vendors (I ordered from Amazon.com) and comes with an enclosure. Once you receive it’s ready to go as a router with no other messing around.

For Ethernet, the RK3568 processor has two integrated Ethernet MACs (GMAC) that support IEEE 1588-2002 (version 1) and IEEE 1588-2008 (version 2) and works with PTP over UDP (layer 3) and over Ethernet (layer 2). The GMAC also supports Jumbo frames (up to 9018 bytes, 9022 for tagged VLAN packets). In addition to this seems to support frames up to 16kB which I’ve never seen or used and definitely don’t have hardware to use with it.

Initial testing shows that linuxptp and the 5.10 Linux kernel “just work” out of the box on FriendlyWrt and was able to synchronize with another device on my network. Driver and hardware support can be verified by reviewing the kernel boot logs: