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

[David J Taylor]

Hal,

Thanks, this had me look closer at the outputs and not all RS232 chip 
breakout boards shift all signals, it seems to be 4-6 lines at most.
I've seen some MAX3232 (RS232 to TTL) converters, but the better ones only 
shift Rx, Tx, CTS, RTS, VCC and GND.

If I read what was suggested here earlier correctly, I need DCD for the PPS 
signal and Rx, Tx for NMEA.
I plan to use this with pfsense/gpsd which lets you choose between rising 
and falling edge for PPS signal processing.

I'll go ahead and order https://www.sparkfun.com/products/11189 as it 
appears to do all RS232 signals and can handle voltages > 5V.

Thank you all again!
==========================================

On a couple of PCs I've installed recently, RS232 add-in boards respond to 
the 3.3V DCD signal, although not to 3.3V data lines.  This from a ublox 6M 
on a Chinese add-in board.  Whilst this would obviously be unsuitable for a 
stand-alone system, if you only need the PPS precision and have a suitable 
source of coarse second, it may be good enough.  It's working for me on a 
Windows-10 PC using the loopback_ppsapi-provider.dll.

Cheers,
David
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