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GPS NMEA Input Command to trigger GPS unit

Posted on 2004-08-11
Medium Priority
Last Modified: 2008-03-10
I have written a bespoke software application to monitor a Leadtek GPS 9532 mouse receiver.

Before I can use my software I must first initialise the GPS unit with Winfast Navigator (the software suppied with the GPS unit).

Once the GPS has been initialised with Winfast Navigator, I can then shut Winfast Navigator down and launch my own software.

I only need to load Winfast Navigator each time I power up the GPS unit.

Whilst most GPS units blindly output the NMEA data, it appears that this Leadtek unit requires an input message to be sent to it before it will output any data.

Can someone please identify what this input message is - its driving me mad.

Regards in advance

Question by:mnewett
LVL 55

Expert Comment

by:Jaime Olivares
ID: 11774941
>I only need to load Winfast Navigator each time I power up the GPS unit.
I thought all GPS need to be configured only once. Will investigate...
LVL 55

Expert Comment

by:Jaime Olivares
ID: 11775143
Ok, I guess your GPS start allways in SIRF protocol, so you have to send a command to switch.
SIRF is a messy binary protocol, but have found a manual:
Command 129 will switch but you have to send extra control characters.
LVL 55

Expert Comment

by:Jaime Olivares
ID: 11775159
Also explained here:

ASCII 129, or
Hex 81
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Author Comment

ID: 11779225
I have tried sending the following string exactly as it appears below - with no carriage returns or line feeds. Still no luck.


Should the message be send as a single string - or should it be split up and sent as 3 strings (start sequence, payload and end sequence)?

Should I be including carriage returns or line feeds?
LVL 55

Expert Comment

by:Jaime Olivares
ID: 11779535
are you sending an ASCII "string"? Or you are sending true binary data?

ASCII string will have 64 bytes long, binary string will have 32 bytes. The correct answer is the sencond one.
Also you must not include CR or LF at the end


Expert Comment

ID: 11827392
Hi mnewett,

Have you found a solution for the GPS initialization? If the question is open, please let us know so we can help you.

Author Comment

ID: 11887372
Thanks for the advice guys - but I've finally found the problem.

The flow control within my application was defaulting to ON instead of OFF - hence the need to run Winfast Navigator in order to initialise the flow control correctly first

I have now found a way of fixing the problem

Accepted Solution

DarthMod earned 0 total points
ID: 12026937
Submitted to PAQ with points refunded (500)

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