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jcpole
10-16-2006, 11:47 AM
Hi all...

I'm trying to use a Propeller to accept serial I/O from a GPS module that outputs NMEA at 4800 baud.· When I activate the GPS module, the Propeller only displays random characters on the CRT.· The GPS module does have a level shifter installed, so that is not the problem.· When I direct the serial output to a BS2px at 4800 baud, this circuit works perfectly, so I'm confused.

Does the Propeller support 4800 baud?· Does the standard serial I/O object from the library support a 4800 baud connection?

Does anyone have any ideas as to why I'm not seeing valid NMEA strings?

The circuit is built with a Propeller demo board, an external LCD TV display, an Axiom GPS module, and a few short jumpers.· Nothing fancy, but it just·doesn't seem to want to·work for me.· I've removed all of my NMEA parsing logic, so the program is nothing but a stripped-down "in one ear and out the other" I/O redirector.

Does anyone have a working serial terminal object/demo program that can run (and has been tested) at 4800 baud?

Thanks...

Jamie


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Jamie C. Pole
Principal Consultant
J.C. Pole & Associates, Inc.
http://www.jcpa.com/

Mike Cook
10-16-2006, 08:42 PM
Jamie,

Try the attached, it will take the NMEA data and sent it to the TV display. Start of an unfinished project, might get you going.

Since the output from the Axiom GPS receiver is already RS-232, I'm using a MAX232 chip to get it to the Propeller. I'm not sure if FullDuplex.spin supports inverted mode. Too many projects, too little time to play!


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Mike (http://www.allsurplus.net/)

Post Edited (Mike Cook) : 10/16/2006 1:22:11 PM GMT

Harley
10-16-2006, 10:54 PM
Jamie,

Look at FullDuplexSerial driver, about 1/2 way down the first page. The 'mode' has 4 bits to control whether or not to invert rx, tx, etc. I have just begun to use this at 38400 baud, should provide what you want at 4800.

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Harley Shanko
h.a.s. designn

jcpole
10-17-2006, 02:05 AM
Thanks for that info - I wasn't sure if a MAX232 would be necessary.· I'll also take a closer look at the driver...

Jamie

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Jamie C. Pole
Principal Consultant
J.C. Pole & Associates, Inc.
http://www.jcpa.com/

Harley
10-17-2006, 02:35 AM
Jamie said...

Thanks for that info - I wasn't sure if a MAX232 would be necessary.· I'll also take a closer look at the driver...



For my application, the Prop interfaces to another board which uses a PIC16F871 which has a uart. I'm presently only using a resistor in series with that tx output to the Prop rx input. So do not need a voltage translator device. Nor will I to a second Prop. Working great.

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Harley Shanko
h.a.s. designn

jcpole
10-17-2006, 05:57 AM
Mike, does the Axiom module accept commands to change the baud rate for NMEA output?

The specs seem to indicate that it does, but those commands are never given (at least not that I can see)...

Thanks...

Jamie


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--
Jamie C. Pole
Principal Consultant
J.C. Pole & Associates, Inc.
http://www.jcpa.com/

Mike Cook
10-17-2006, 11:58 AM
It's in the NMEA documentation, (look for $PSRF100), you'll need to compute the checksum for the sentence, to make it work.

Also the 'Conductor' program will allow you to configure baudrate.



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Mike (http://www.allsurplus.net/)

Post Edited (Mike Cook) : 10/17/2006 4:02:35 AM GMT

jcpole
10-17-2006, 11:27 PM
Thanks Mike...

Jamie

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--
Jamie C. Pole
Principal Consultant
J.C. Pole & Associates, Inc.
http://www.jcpa.com/