[time-nuts] NMEA Checksums

Chris Kuethe chris.kuethe at gmail.com
Wed May 28 02:42:58 EDT 2008

I can't think of a good reason to not checksum delimiters (in any protocol).

If delimiters count, and the checksum matches, you can have more
confidence that the message is structurally sound. Otherwise you can't
be sure if you missed a delimiter or which one until you start
unpacking the message. Since I haven't seen the NMEA spec, I can't
tell you if TXT is a legal message type - but ublox receivers emit
$GPTXT messages. In some cases these free-form messages might have
commas in them, and those commas may be information-bearing.

And it's just easier to keep adding characters until you hit the
ending delimiter or maximum sentence length than it is to keep
detailed state on what you've checksummed,

On Tue, May 27, 2008 at 11:26 PM, Matthew Smith <matt at smiffytech.com> wrote:
> Quoth Chris Kuethe at 2008-05-28 15:54...
>> Commas matter. The checksum runs over every character between the
>> leading '$' and the '*' delimiter.
> Ta!  That means I can use your Oncore function pretty well as-is.
> Cheers
> M
> --
> Matthew Smith
> Smiffytech - Technology Consulting & Web Application Development
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GDB has a 'break' feature; why doesn't it have 'fix' too?

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