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lew247

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Joined: 23/12/2015
Location: United Kingdom
Posts: 1702

Posted: 06:36am 20 Jan 2016

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I've built the GPS Synchronised Clock as per Silicon Chip's magazine in March 2009
Modified the clock module, i'm just waiting for one part to arrive

I have run into a problem though, the gps module I have defaults to 9600 baud, not 4800
Is there any way to change the code in the program to 9600 instead of 4800
alternatively I need to find a way to change the gps setting to 4800

I have 2 gps modules, one is the ultimate gps breakout board which works best, its more sensitive
The other is a NEO-6M module
both default to 9600

I have a pc and no arduino built at the moment, so any talking to the gps module will have to be through the pc

unless I can figure a way to change the code to work at 9600 obviously.

Any ideas or suggestions?

jman

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Joined: 12/06/2011
Location: New Zealand
Posts: 711

Posted: 08:46am 20 Jan 2016

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Hi
You can change the line below

open "COM1:4800" As #1 ' open the GPS serial interface

open "COM1:9600" As #1 ' open the GPS serial interface

Regards
Jman

matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 10209

Posted: 08:47am 20 Jan 2016

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Assuming this is the same project as in EPE May2011 (they normally publish the same projects two years behind) then you can change the source as follows:

Change this line:

MOVLW h'33' ; now set SPBRG reg for 4800 baud async serial comms
mode

to:

MOVLW h'19' ; now set SPBRG reg for 9600 baud async serial comms
mode

With a bit of detective work you could upload the hex file from the chip into your programmer, find the relevant hex number 33 and patch it to 19 and then reprogram the chip. Alternatively recompile the source - you would need to download the relevant development environment from Microchip

Edited by matherp 2016-01-21

lew247

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Joined: 23/12/2015
Location: United Kingdom
Posts: 1702

Posted: 08:52am 20 Jan 2016

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Thanks
I figured the easy way, use a terminal program and send the command $PMTK251,4800*14<CR><LF>
What had me totally confused for a long time was how I worked out the checksum, luckily found a calculator online :)

lew247

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Joined: 23/12/2015
Location: United Kingdom
Posts: 1702

Posted: 09:18am 20 Jan 2016

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Found a problem
Although I changed the baud rate to 4800 and it works great, if I disconnect power from the gps module it resets back to the default 9600 baud
Seems the only hope is to somehow modify the baud rate of the program to match
which is highly unlikely

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