4 ms·
The most straightforward thing is to just run the CPU with an accurate clock frequency. You'll have to replace the Quartz next to the clock-generation chip next
by cnvogel 11y ago
The most straightforward thing is to just run the CPU with an accurate clock frequency. You'll have to replace the Quartz next to the clock-generation chip next to your CPU/Chipset by something which is very accurate.
http://phk.freebsd.dk/soekris/pps/ http://phk.freebsd.dk/soekris/pps/
https://deltafabri.wordpress.com/2015/03/08/under-60-ns-an-atomic-stratum-1-ntp-server-hardware/ https://deltafabri.wordpress.com/2015/03/08/under-60-ns-an-a...
For the cost, it's about $150 or so for a used GPS with precise 10 MHz reference frequency output, there's a different PLL IC (different from the ClockBlock module) from Silabs which is available from Adafruit for <$10, but I don't know if the xtal there can be exchanged for a 10 MHz frequency. The C-revision of the used IC can be, though... https://learn.adafruit.com/adafruit-si5351-clock-generator-breakout/overview https://learn.adafruit.com/adafruit-si5351-clock-generator-b...
- jacquesm 11y agoThat's straightforward if you're a hardware hacker, it wouldn't slow me down much but I think that for most software oriented people building your own time-server and verifying that it works is out-of-scope. GP probably meant to hook this straight into their PC and the CPU you refer to is actually the CPU of a separate board rather than the main CPU (where thermal drift will usually make the oscillator less than reliable over longer periods of time).
- cnvogel 11y agoOk, if you want something off the shelf, then there are things like this: https://www.meinbergglobal.com/english/products/pci-express-clocks.htm https://www.meinbergglobal.com/english/products/pci-express-... But I don't know what functionality they actually provide available over the pci-express port, if one is unlucky, it's only the serial port to the GPS receiver ;-).