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GPS NMEA Input Command to trigger GPS unit

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

1 Solution
Jaime OlivaresSoftware ArchitectCommented:
>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...
Jaime OlivaresSoftware ArchitectCommented:
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.
Jaime OlivaresSoftware ArchitectCommented:
Also explained here:

ASCII 129, or
Hex 81
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mnewettAuthor Commented:
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?
Jaime OlivaresSoftware ArchitectCommented:
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

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.
mnewettAuthor Commented:
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
Submitted to PAQ with points refunded (500)

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