More FPU questions

halfblinddado

Hello,

After a lot of mucking around I finally got this to work. However' In the code snippet below I get the an output of 135 degrees which is correct.

'

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Variable Definitions

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coord1········· VAR·· Word············· ' signed word variable
coord2········· VAR·· Word············· ' signed word variable
coord1To VAR Word
coord2To VAR Word
junk VAR Word
'

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Generated Code

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·· coord1To = 25··· 'y
·· coord2To = -25··· 'x
·· coord1 = 0····· 'y
·· coord2 = 0····· 'x
·· coord1 = coord1To - coord1
·· coord2 = coord2To - coord2
·· SHIFTOUT FpuOut, FpuClk, MSBFIRST, [noparse][[/noparse]SELECTA, heading, LEFT,
··· LOADWORD, coord1.HIGHBYTE, coord1.LOWBYTE, FSET0,
··· LOADWORD, coord2.HIGHBYTE, coord2.LOWBYTE, ATAN2, 0, RIGHT, FSET0]
·· SHIFTOUT FpuOut, FpuClk, MSBFIRST, [noparse][[/noparse]SELECTA, heading,
··· FWRITE0, $42, $65, $2E, $E1, FMUL0]
· ' Heading is output *180/Pi

· DEBUG CR, "Heading = "
· GOSUB Print_Float
· DEBUG CR, "Done.", CR
· END


However if I change the input to the following I get -135 degrees? Shouldn't I get 225 degrees?

·· coord1To = -25··· 'y
·· coord2To = -25··· 'x
·· coord1 = 0····· 'y
·· coord2 = 0····· 'x

As you can see I'm no math wiz but I would like to know how to get the degrees for the complete circle.

Thanks,

Mike

Carl Hayes

Notice that -135 degrees is the same direction as 225 degrees. If you want your answer always positive, simply add 360 if it's negative.

If you really want a brain teaser, try to devise an algorithm for averaging several headings.· It's surprisingly hard to come up with a way that will work for any combination of headings.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
· -- Carl, nn5i@arrl.net

Post Edited (Carl Hayes) : 2/16/2009 5:55:01 AM GMT

halfblinddado

Carl,

Thanks for your reply. That works great. I knew it had to be something simple.

Now if I can just get the fpu to determine if the output is a negative or positive number.

Mike

halfblinddado

Ok So now I am able to get angles in degrees I modified the code and was able to find the heading from the google campus to hangar 1 at moffet field on Google maps. I took out the degrees and just used the fractional minutes.

Can someone tell me how to get the whole number, degrees and minutes such as -122.083893 into the FPU?

Thanks,

Mike

·· coord1 = 19036··· 'y
·· coord2 = -2653··· 'x
·· coord1To = 24785···· 'y Current position
·· coord2To = -3235····· 'x Current position
·· coord1 = coord1To - coord1
·· coord2 = coord2To - coord2
·· DEBUG DEC coord2.HIGHBYTE, CR
·· DEBUG DEC coord2.LOWBYTE, CR
·· SHIFTOUT FpuOut, FpuClk, MSBFIRST, [noparse][[/noparse]SELECTA, heading, LEFT,
··· LOADWORD, coord1.HIGHBYTE, coord1.LOWBYTE, FSET0,
··· LOADWORD, coord2.HIGHBYTE, coord2.LOWBYTE, ATAN2, 0, RIGHT, FSET0]
·· SHIFTOUT FpuOut, FpuClk, MSBFIRST, [noparse][[/noparse]FSTATUSA] '
·· GOSUB Fpu_Status····························· 'status 1 = negative 0 = positive
·· DEBUG ? status_Sign, CR······················ '
··· IF status_Sign = 0 THEN
····· SHIFTOUT FpuOut, FpuClk, MSBFIRST, [noparse][[/noparse]SELECTA, heading,
····· FWRITE0, $42, $65, $2E, $E1, FMUL0]
··· ELSE
····· SHIFTOUT FpuOut, FpuClk, MSBFIRST, [noparse][[/noparse]SELECTA, heading, LEFT, LEFT, FSET, heading,
····· FWRITE0, $42, $65, $2E, $E1, FMUL0, RIGHT, FSET0, LOADWORD, $01, $68, FADD0,
····· RIGHT, FSET0]
··· ENDIF
· ' Heading is output *180/Pi. For negative numbers add 360

· DEBUG CR, "Heading = "
· GOSUB Print_Float
· DEBUG CR, "Done.", CR
· END