Any Benefit? Modifying GPS Module's baud rate

fish

Hi all,
Dumb·question, but it never (usually)·hurts (physically)·to ask.
Is sx-blitz going to be the cheapest and/or easiest and/or·only way to modify the gps module's baud rate?

Johnnymac's gps hacking doc.
http://www.parallax.com/dl/docs/cols/nv/vol7/col/NV139.pdf

I'm not at the point to answer the question 'In that 1000ms gap between·NMEA data·updates, will the increased output rate of the module·provide any usable benefits ?'.
I'm really just·thinking about some optimizations down the road.

Anyone who has tweeked the gps mod this way offer any advice or a few words on your experience?·
Any thoughts about this would be appreciated.

thx
fish

<edited>I forgot to mention that I am currently using the Propeller to talk to the GPS module.



Post Edited (fish) : 5/15/2007 2:37:53 PM GMT

M. K. Borri

What I find is that the GPS generally behaves as if taking 1 position reading per second regardless, but the full complement of NMEA strings takes longer than 1 second to send -- thus for example why sometimes the GPRMC string is different than the GPGGA coordinates wise, they were taken on different seconds.

What you can do instead of having it up the baud rate is have it only output the string you are using (GPRMC for me), I know the LocSense EB40 lets you do that and that's really the absolute lowest end for GPS modules, so Parallax's probably does have an option to do it.

Do keep in mind that the NMEA standard specifies 4800 baud, so if you have to care about that sort of thing, you will have to reduce the output rather than up the baud.

fish

Thanks M. K.,
I use the extended fullduplexserial now to parse only the sentence and element I need (GPRMC for me also).
I am using a nokia color lcd and spin (except for the spi engine which is assembly) which is ok, but not super fast.
I even optimize to only display what has changed since last sentence was read.
Basically I do my screen updates in that 1 sec in between NMEA updates.
I still have to implement my tracking history lines and waypoints, etc. so there a few unknowns.
Any speed gained by upping the baud seems like a good thing. But it may not be enough to matter or bother with.

Thanks for the feedback.
fish

M. K. Borri

Well, again, if you can get 1 position fix per second, it's not worth it to go beyond that. If you're currently getting 1 fix every 2 seconds, there IS room for improvement [noparse]:)[/noparse]

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http://forums.parallax.com/showthread.php?p=650217

meow, i have my own topic now? (sorta)

Chris Savage

Fish,

Bear in mind that while you could increase the baud rate for the SX sending data to the host, the Polstar GPS unit is still only sending its data at 4800 bps to the SX every second and you cannot increase that. Take care.

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Chris Savage
Parallax Tech Support

M. K. Borri

In that case, try to reduce the sentences being sent (just send gprmc and parse that for example).

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http://forums.parallax.com/showthread.php?p=650217

meow, i have my own topic now? (sorta)