NMEA Checksum?

MJG2514

······ Hi Folks,
······················I have been working on interfacing a BS2px with a GPS Engine. The commands sent to the GPS Module must have the correct checksum to be accepted. Is there a program out there for the BS2 family or a program that can be downloaded·for XP or Vista for this calculation?·
····················· I am aware that it is the XOR of all bytes between the preamble "$" and the "*". How do you do this "by hand"?

························································································ Thanks,

stamptrol

I've interfaced several gps units and never been asked for a checksum. Are you sure your gps can't be configured to be queried by a straight ASCII string? it will make life so much easier.

The other way to do it is to pick one query string that will give you the data you need. Then manually calculate the checksum. Put that query string
into the Stamp program, complete with the checksum. Then, instead of calculating checksum on the fly each time, just fire off the pre-packaged string.

Cheers,

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Tom Sisk

http://www.siskconsult.com
·

Chris Savage

Windows calculator can do XOR...so if you can translate all the ASCII codes for the characters you can do it manually.

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Chris Savage

Parallax Engineering
50 72 6F 6A 65 63 74 20 53 69 74 65
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Jonathan

Is this a Motorola Oncore unit? If so send me a PM, I have some code that will do the checksum, it is very simple.

Jonathan

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