[ntp:questions] almost decided which new PPS GPS to buy
David J Taylor
david-taylor at blueyonder.co.uk.invalid
Sun Mar 4 18:51:19 UTC 2012
> Hi all,
> From my reading, it appears that I need to add the following to the Sure
> Electronics package of parts:
> 1) DB-9 Male - DB-9 Female serial cable
Correct. I got mine from Amazon. Search for "2m 9 Pin Serial / RS-232
Extension Cable M-F".
> 2) Motherboard header - DB-9 port adapter
Correct, if you don't already have a serial port on your PC. Check that
the motherboard has the COM port header, of course!
> 3) Plastic box for mounting. Misc hardware like screws, standoffs, etc.
> (David T. or others, I don't suppose you can suggest any specific part
> numbers for those hardware items from Radio Shack [do you have those in
> the UK], Mouser, or DigiKey. Just thought I'd ask.)
I used N90BQ from Maplin.
and filed out the openings for the connectors.
> My plan of attack is as follows, although the sequence may vary:
> A) Get the unit working "at all", using USB NMEA data only. I would
> hope to see performance equal to my BU-353.
I only use USB for power. Not data.
> B) Get the unit working with NMEA data from the RS-232 port, going
> through a Trendnet TU-S9 USB - Serial converter, based on the Prolific
> chipset. Performance should, again, be similar to the BU-353 (which
> also uses the Prolific chipset internally).
> C) Get the unit working with NMEA data from the RS-232 port, going to a
> real serial port. I have to tinker with the motherboard on another
> computer to do that.
Find an old computer with a serial port, and run the software Sure
> D) Get the unit working with NMEA + PPS, with data from the RS-232 port,
> going through the TU-S9, which claims to pass all the handshaking
> signals. I'll have to do the mods that David recommends on the board
> for this. Hopefully, the same procedure will still work on the recent
> boards. This is where I'm hoping to get + / - 1 ms performance.
> E) Get the unit working with NMEA + PPS, with data from the RS-232 port,
> going to a real serial port on the other computer.
> This should be an interesting adventure, hopefully ending with a time
> server running at 100 us accuracy or better.
You are confusing me with how many computers you have! Designate one as
your stratum-1 server, and get it right, with the serial I/O, adding the
header should you need it.
As you already have something which works, I would take a much more
- get serial I/O somehow and check the unit works, applying power via the
- carefully, add the PPS/DCD modification (two wires to solder) which
translates the TTL-level from the board to the RS-232 level required by
- use my Serial LEDs program to verify the PPS signal.
- configure NTP around the new unit.
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