[time-nuts] Virgin time nutter fell at the first M12+ hurdle

paul swed paulswedb at gmail.com
Wed Jun 11 15:26:29 EDT 2014


Chris is correct many GPS receivers do not output anything till queried.
Further it seems the TX and RX data may need to be swapped. That has bagged
me a few times because it depends on the perspective. Easier to just try
swapping them.
The max series does indeed perform the the logic translation a +5 signal
ttl/cmos to -12V rs232.
Regards
Paul
WB8TSL


On Wed, Jun 11, 2014 at 1:50 PM, Chris Albertson <albertson.chris at gmail.com>
wrote:

> First off if you are getting PPS on the PPS pin the GPS is working.   By
> default I don't think the MT12 outputs any serial data unless in response
> to a query.   By default it is not a NEMA device.
>
> The protocol is binary so it would be rely hard to control it with a Window
> terminal  program
>
> The simplest way to use the MT12 is to connect it to an NTP server.  You
> may not want to run NTP, you want a GPSDO but NTP knows how to get the MT12
> running and NTP has a good log file that you can read to track what the GPS
> is doing.    There are other software for controlling MT12 and other Oncore
> series GPSes that are better but NTP is already installed on many computers
>
> The other thing to watch with serial RS232 is the polarity.  I'm pretty
> sure the MAX chip acts as an inverter.  That might be good because RS232
> uses negative logic with a low voltage being a "one" and a higher voltage
> being a "zero"   Well at least on the data pins, the control, I think is
> positive logic.  If you get the polarity wrong it does not work
>
>
>
> On Wed, Jun 11, 2014 at 9:04 AM, Stephen <si at 2si.co.uk> wrote:
>
> > Hello everyone,
> >
> > After reading quite a bit from your archives i've decided to try a put
> > together a 10MHz reference.
> >
> > I've picked up a oncore M12+T GPS card and have tried to initialise it
> but
> > without any success thus far.
> >
> > The user manual for the M12+T seems to suggest that i should be able to
> > hook the txd and rxd pins to a MAX3232 and be able to use the Winoncore
> > software to configure the card.
> >
> > At power up the M12+T pins 1 & 2 are at 3V. After 10 seconds pin 2 sinks
> > to 0V, pin 1 idles at 3V and pin 4 give 1PPS.  No serial output from the
> > card at all.
> >
> > Anyone have experience of connecting an M12+T to rs232?
> >
> > Stephen
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>
>
>
> --
>
> Chris Albertson
> Redondo Beach, California
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