I have complete instructions on how to use a raspberry pi as an NTP server.
Ping me if you want them Chip Blach On Fri, Jun 17, 2022, 8:08 AM David Taylor <david-tay...@blueyonder.co.uk.invalid> wrote: > On 17/06/2022 03:03, Daniel O'Connor wrote: > >> Yes, Thiebaud, USB is not good enough for PPS signals! > > This is absolutely false. > > > > If you are using it for NTP then GPS+PPS over USB is quite adequate > (from personal experience). > > > > Ian Lepore (RIP) who worked for Micro Semi and worked on FreeBSD did a > bunch of tests on a PPS over USB setup and found it more than > > acceptable for keeping a PC in (good) time. Here's the thread: > https://lists.freebsd.org/pipermail/freebsd-arm/2019-August/020263.html > > > >> See if your motherboard has a true serial port - perhaps just as a > header but not a back connector. If not, just set the offset of the PPS to > ~10.3 milliseconds (10.3 - IIRC the offsets are in milliseconds but please > check). Plus or minus 10.3, try it and see! Not perfect, but better than > nothing. > >> > >> You might find better results using that GPS/PPS with a Raspberry Pi as > a stratum-1 server and offering that as a server on your LAN. > > The next level would be something where you can do an input capture on > the PPS I don't think there are any pre canned solutions. I made one with a > Beagle Bone Black and a uBox GPS module but it's not exactly turn key. Or > for a server then you would need a fancy (ie $$$$) internal card. > > > > The Raspberry Pi does not have an input capture timer, but I believe you > can do better with DMA hackery (I haven't tried though). > > If a 125 us uncertainty in the PPS is something you can tolerate, so be > it. If > you are bothering with PPS then presumably you want better accuracy than > can be > achieved without it. > > No need for DMA hackery. Standard NTP with the Raspberry Pi can handle > PPS on > a GPIO signal with a couple of edits to allow the PPS support already > built > into the kernel to be attached to the appropriate GPIO pin. Not out of > the > box, but very little effort required. > > The Raspberry Pi can act as a server for hundreds of clients. If you mean > a > PC-based Windows server, that's not something I would immediately > recommend, > but if you must a £20 serial card may be all you need to add. > > -- > Cheers, > David > Web: http://www.satsignal.eu > -- > This is questions@lists.ntp.org > Subscribe: questions+subscr...@lists.ntp.org > Unsubscribe: questions+unsubscr...@lists.ntp.org > > > > >
