Date   : Sun, 21 Nov 2010 21:25:34 +0100
From   : rick@... (Rick Murray)
Subject: Using a Beeb for engine monitoring

On 21/11/2010 21:00, Mark Usher wrote:

> You could use the serial output of a GPS locator, I believe that some can
> output speed and distance and just co-ordinates.

Pretty much every GPS ought to do at least that. As it will probably 
communicate using NMEA "phrases", it may be best to simply pick up the 
ones you need and ignore the rest. On numerous GPSs, it is possible to 
fine-tune the data offered, and also the refresh rates, but this will 
rely upon non-standard "control" codes.

You might want to receive the info listing the number of active 
satellites and also the xDOP values, for this provides a suggestion as 
to the accuracy of the data. I have been "moving" across the back field 
when completely motionless, and while I have an exact fix of my 
location, even with 9 satellites in view, the height is constantly 
altering between 78 and 95 metres. But then we're dealing with distances 
measured using differences of the speed of light from constantly moving 
objects - it's a wonder the system works at all.

You can see a (partial) example of the NMEA info at:
   http://www.heyrick.co.uk/blog/index.php?diary 100912

I think most GPSs work at either 4800bps or 9600bps, so sufficient for a 
Beeb to talk to it.


> Then you only need the fuel level from the car. You use Google maps,
> err, I mean the Domesday Disc to plot the route ;-)

I'm not sure the route actually matters, you'd just need to know the 
distance travelled, and that you ought to be able to determine 
point-by-point from the GPS replies and some scary maths. Indeed, the 
system could be made quite adaptive by knowing the speed you are 
currently moving so able to predict MPG/estimated from these inputs.
Or, at the very least, it won't be any less accurate than the Windows "x 
minutes remaining" file copy report.


Best wishes,

Rick.

-- 
Rick Murray, eeePC901 & ADSL WiFI'd into it, all ETLAs!
BBC B: DNFS, 2 x 5.25" floppies, EPROM prog, Acorn TTX
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