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Jan 10, 2007, 03:25 PM
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C-compiler - decoding NMEA


I am waiting for my BlackBox platform. In the meantime I can experiment with a 16F628 on a breadboard

I downloaded a C-compiler (http://www.sourceboost.com/Products/Products.html). Setting up (it contains its own IDE) and writing the first application was almost trivial. I wrote some code on a PC for parsing NMEA messages and it functioned right away on the 16F628.

I am now developing code on a PC to calculate bearing and distance between 2 points. First I wrote code using floating-point operations and trigonometric functions. I already eliminated the latter and now try to circumvent the floating-point operations.
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Jan 10, 2007, 05:54 PM
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Out of band data


It should be possible to encode GPS data in the audio and display it on an LCD panel for a lot less money and screen real estate. There's also the vertical blanking interval which is probably accessible for a PIC.
Jan 11, 2007, 10:20 PM
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Quote:
Originally Posted by FredericG
I already eliminated the latter and now try to circumvent the floating-point operations.
how hard is that to do? had you considered using one of these. i haven't used it but it's something i'd like to try when i get to buildling my own hardware. i first need to find out how seamless code is when you're using a c compiler. would be nice to just write your c code with floats, compile, load, and you're done.
Last edited by 4mla1fn; Jan 11, 2007 at 10:40 PM.
Jan 12, 2007, 04:10 AM
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Quote:
Originally Posted by Jack Crossfire
It should be possible to encode GPS data in the audio and display it on an LCD panel for a lot less money and screen real estate. There's also the vertical blanking interval which is probably accessible for a PIC.
I understand that you propose to beam down the raw data via the audio (this boils down to a MODEM I suppose) or in the “dead” time (not sure how to call it) in the video signal or perhaps use a mechanism used by teletext. Once on the ground we have much more processing power and possibilities. However, even than, I would want to place the calculated data on the screen.
I have been thinking about this approach. I did not do it because:
- I want to calculate the heading and distance to pilot on the plane anyway for the rudder-home functionality
- With my knowledge, it would increase complexity.

Perhaps it would be nice idea for a next project.


Frederic
Jan 12, 2007, 04:19 AM
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Quote:
Originally Posted by 4mla1fn
how hard is that to do? had you considered using one of these. i haven't used it but it's something i'd like to try when i get to buildling my own hardware. i first need to find out how seamless code is when you're using a c compiler. would be nice to just write your c code with floats, compile, load, and you're done.
There are also libraries for floating point operations but I suppose they are big. The compiler supports 32 bit operations. This provides good resolution but it is fixed point. So you constantly have to watch for under- and overflow.
I am working on code that only uses 32 bit integer operations and use as prerequisite that the distance is not bigger than 5000m, which is for sure acceptable for this project. I am almost there and it does not look too difficult. I also need a sinus-function and for this a use a lookup table (array) with pre calculated values.

Frederic
Feb 07, 2007, 01:53 AM
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GPS Telemetry - ARPS


Quote:
I understand that you propose to beam down the raw data via the audio (this boils down to a MODEM I suppose) or in the “dead” time
Interesting (OLD) thread on this subject: https://www.rcgroups.com/forums/show...98#post3713098

http://www.rc-cam.com/forum/index.php?showtopic=1691
Last edited by FredericG; Feb 22, 2007 at 12:04 PM.


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