[time-nuts] Connecting my Oncores

Matthew Smith matt at smiffytech.com
Tue Apr 1 22:32:50 EDT 2008

Hi Folks

Now that I've got a computer ready to be a time server, I am now 
fiddling about with my GPS modules, checking that they are working and 
the like.

As I have yet to build and interface board for my Trimbles (requires a 
very fine pitch IDC connector, which is on backorder), I am testing my 
Oncores, for which I have an interface box that I got through eBay and 
have hacked to pass the 1PPS signal to DCD (this was unconnected when I 
got it).

I tried talking to all three units using minicom - a VP and to GT+s at 
both 9600bps and 4800bps.  The VP kept spouting binary stuff at me, 
which seemed to make most sense at 9600bps.  The GT+s wouldn't do a thing.

I then fired up Windows through VMware (quite surprised to see that it 
found my USB to serial adapter), acquired a copy of VisualGPS and, after 
changing the port speed, managed to get the VP initialised so that it is 
now sending NMEA data, which I can now get via minicom under Linux.

What is puzzling me about the VP is why I was unable to get this working 
myself.  Through minicom, at both 9600bps and 4800bps, I typed @@Ci, 
which the manual tells me should get the device into NMEA mode.  Nothing 
happened at all - didn't even get the characters echoing back at me. 
Yet VisualGPS managed to do this OK.

One of the GT+s is being totally dumb - to start with, both were, one 
has now initialised at 4800bps and is spewing NMEA data, but is not 
registering any satellites or a position - does this just need to be 
left to its own devices for a while?  Don't really know what to do with 
the other one; there is a rechargable lithium battery on it - it's 
showing 1.75 Volts.  Wonder whether I should unsolder this and try the 
unit without it.  Really wish there was SOMETHING on the boards - a 
jumper or whatever - that would guarantee me a factory reset.



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

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