[time-nuts] GSyncQ GPS Evalution Kits && NTPns
bruce.griffiths at xtra.co.nz
Fri Apr 25 06:06:58 EDT 2008
Pekka Niemelä wrote:
> Hi Bruce, thanks for bearing with me. :)
> On 4/25/08, Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:
>> If you want, you can easily construct your own external RS422 to RS232
>> Just use a Max 232 to convert the RS232 signals to TTL/CMOS and connect
>> RS422 receiver and transmitter chips to that.
>> RS 485 transceivers chips can also be used instead of RS422 transmitters
>> and receivers, just connect them as drivers or receivers as required.
>> If you need a circuit schematic I can send you one.
> Hmm, if you would have schematics that would be really great. Can I download
> them from somewhere? I'm not 100% that I understand what you're saying, but
> I guess the schematics talk more than thousand words. :)
I need to create them first, I can then place them with my collection of
circuits, references etc on Didier's site:
Should be ready by 1200 UTC.
What I am really saying is that if one uses a few chips on a circuit
board one can just connect the GPS cable to the 2 RS422 receivers and RS
422 transmitters on the card.
A Soekris serial port would then connect to the RS232 transceiver chip.
The TTL/CMOS signals from the 2nd RS422 chip would connect to the
appropriate Soekris header pin so you can use the higher resolution timer.
No plug in RS422 card is then required.
Remember of course that the RS422 signal is differential and the cable
pair associated with each RS 422 signal has to be terminated in in the
correct characteristic impedance at the receiver (~100 ohms).
Can you buy components from Farnell or RS components these appear to be
good sources for some parts of Europe (for Germany at least)?
If so I can easily check the availability of the required parts.
> The other option is ofcourse to just buy the transciever. But even in that
> case I would need to drop the voltage with the max 232? That is, the 1PPS
> signal that we drive into the Soekris?
> Novatel also use Deutsch connectors on some of their enclosures.
> Hmm, so it's an industry standard? Wikipedia doesn't know anything about it.
> warm regards,
> P. Niemelä
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