[time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

STR . strykar at hotmail.com
Sat Aug 13 22:32:13 EDT 2016


I recently bought 2 ublox PCI-5S mini-PCI GPS modules and have ordered a PCengines APU2C4 board I hope to install it in.

Others have found it can provide PPS output http://emerythacks.blogspot.in/2013/01/u-blox-pci-5s-cheap-gps-module-for-your.html

This is the x-64 AMD SoC by PCengines - http://www.pcengines.ch/apu2c4.htm

Schematics - http://www.pcengines.ch/schema/apu2c.pdf

User manual (Page 8 has a nice overview of the board) - http://www.pcengines.ch/pdf/apu2.pdf

I would like to install and power the GPS from the mini-PCI slot and output PPS directly on to one of the serial ports on the SoC board for ntpd.

Since mini-PCI uses  3.3V and serial uses 5V I guess, I'm not sure how to achieve this and am concerned I might fry the board.

Do I need a MAX 232 voltage converter?

Can this be done using the mini-PCI slot for power?

I have posted my issue on the PCengines forum and got 1 response so far that suggested I connect to COM3 on the GPIO header  -


I'm not sure where exactly, these are the GPIO pins on the board http://imgur.com/a/bAZLb

When someone says "LPC serial IRQ and system interrupt latency will add up to noticeable jitter" does that mean the jitter would be equally bad from any serial port on the board or just from the 3rd serial off the GPIO pins?

Here, someone else claims the PPS should have less jitter in a similar setup - http://pcengines.info/forums/?page=post&id=CD275C4D-8050-408A-BD16-6F50468C74C2

I'm hoping someone here could help me out with this as I'm well in over my head by now.



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