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

KD0GLS kd0gls at mninter.net
Wed Jun 11 21:10:14 EDT 2014


Note however that the M12+T’s I/Os are 3V, not 3.3V and not 5V.

On Jun 11, 2014, at 19:46 , paul swed <paulswedb at gmail.com> wrote:

> 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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