[ntp:questions] Cheap ($29.90) GPS receiver
Hal Murray
hal-usenet at ip-64-139-1-69.sjc.megapath.net
Mon Apr 19 17:29:32 UTC 2010
>How precise can a 4800 baud serial port be in determining the start of a
>start bit? About 1/4800s i.e. about 200 microseconds? Don't the chips
>sample at 8 or 16 times baud rate, so couldn't the start bit be determined
>to ~25-30 microseconds? And if the baud rate was lot higher (the unit
>claims 57600 baud)?
>
>You would be using the unit in a slightly different mode to an existing
>GPS - just detecting the start of an RS-232 burst for the PPS, and then
>reading a message for the actual value....
What you describe could be made to work quite well, but I've never
seen one that works that way.
The data sheet says 1 microsecond. It also says SiRF chip set.
All the SiRF units that I've tested are horrible. They aren't even
trying for good timing.
My guess is that the 1 microsecond was copied from another data
sheet that did have a PPS signal.
If anybody tests one of these, please let us know how well it works.
--
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