[time-nuts] Connecting my Oncores

randy warner randy at geodetics.com
Wed Apr 2 20:39:58 EDT 2008


The battery can indeed cause some problems if you don't have the software
necessary to reset the receiver to a known state. The simplest thing to do
is get a copy of Rick Hambly's TAC32 at cnssys.com. TAC32 will light up just
about any Moto receiver ever made no matter what state it is in. If TAC32
can't talk to any given receiver the receiver is most likely toast. I'm not
sure how smart gpsd is, but it may not know about switching the receiver
between binary and NMEA mode. Since the gpsd commands you show in your email
specify 9600 baud, I assume you want binary? Visual GPS will only talk to
Moto receivers in NMEA mode at 4800 baud. It is NOT able to switch a Moto
receiver into NMEA from binary.

Randy Warner

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Matthew Smith
Sent: Tuesday, April 01, 2008 8:57 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Connecting my Oncores

Quoth Hal Murray at 2008-04-02 14:08...
>> My manual suggests you need to send
>> @@Ci<mode><cksum><CR><LF> 
> I had a similar problem a while ago.
> I wrote a simple python hack to compute the checksum.  The manual probably

> has an example you can test it on.
> It's also worth checking gpsd.  It knows how to talk to lots and lots of
> units and can smash some of them into a useful state.

Thanks for the suggestions.  I'll play around in Perl to get something 
going and then translate it to C for use as a start-up routine.  (I was 
going to put on of the GT+s in a Nixie clock, so Perl is out of the 
question there ;-))

The GT+s are definitely behaving strangely; I just connected the one 
that finally decided to talk to me to the computer that will be the time 
server and fired up gpsd:

# gpsd -D 4 -n -N /dev/cua00
gpsd: launching (Version 2.34)
gpsd: listening on port 2947
gpsd: running with effective group ID 0
gpsd: running with effective user ID 0
gpsd: opening GPS data source at '/dev/cua00'
gpsd: speed 9600, 8N1
gpsd: garmin_gps not active.
gpsd: no probe matched...
gpsd: gpsd_activate(1): opened GPS (6)

Didn't recognise it, just sat there.  (The documentation mentions 
specifically that it knows about GT+s.)  I re-connected the module to 
the machine with VisualGPS, now I can't get it to talk to me again. 
This doesn't seem right - either the thing should work or not.  I do 
have my suspicions about those on-board batteries and wonder if I would 
be better off without them.

Think I'll use the VP for the time server and leave the GT+s for further 
experimentation unless anyone just happens to know why they aren't 
playing along.



Matthew Smith
Smiffytech - Technology Consulting & Web Application Development
Business: http://www.smiffytech.com/
Personal: http://www.smiffysplace.com/
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