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

Attila Kinali attila at kinali.ch
Sun Aug 14 05:07:40 EDT 2016

On Sun, 14 Aug 2016 02:32:13 +0000
"STR ." <strykar at hotmail.com> wrote:

> 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.

It depends on where you want to connect it to. You have 3 choices:

1) COM1 after the level converter
2) COM1 before the level converter
3) COM2

Option 1) needs +/-5V, options 2) and 3) work with 3.3V.
But: both options 2) and 3) require you soldering directly
onto the APU board: for 2) you need to unsolder U37 and you will
lose your console serial port. For 3) you need to solder wires
directly onto the pins of U9 as the signals have not been broken
out onto testpoints.

For more information, see the APU schematics and the NCT5104D datasheet.

			Attila Kinali
Malek's Law:
        Any simple idea will be worded in the most complicated way.

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