ColdFire/68K Microcontrollers and ProcessorsのトピックRe: trigonometric functions under ColdFire V1

trigonometric functions under ColdFire V1

royjf — Thu, 05 Mar 2009 22:53:31 GMT

Hi, I would like to do arcsinus function (asin()) under coldfire V1 (PCF51AC256AVLKE) but I can't figure out where I can find it. I tried including math.h but it doesn't help.

Any solution ? any workaround using trigonometric identity ? I don't care of computing time (as far as it stays within a certain limit) but I would like to avoid a lookup table.

Thanks

JF Roy

Re: trigonometric functions under ColdFire V1

Kan — Fri, 06 Mar 2009 09:38:51 GMT

Hi JF,

though I am not very familiar with PCF51AC256AVLKE,I know there is a asin() function in the C_4i_CF_Reg(Std)ABI_MATH.a,Have you added this lib in your project?you can find it at the folder C:\Program Files\Freescale\CodeWarrior for Microcontrollers V6.2\ColdFire_Support\msl\MSL_C\MSL_ColdFire\Lib if you install CodeWarrior in that way.

B.R

Kan

Re: trigonometric functions under ColdFire V1

royjf — Fri, 06 Mar 2009 22:47:42 GMT

Thanks

I tried to include directly the file.a but it is'nt working because the file format is not correct (can't include a file.a like if it was a file .h) I am using codewarrior for microcontrollers v6.1 maybe there is something to do with it...

Anyway, so far I created a lookuptable of 37 array of 2 int. The table is not linearly sampled and the points are closer where the asin function changes more quickly. I do "real time" linear interpollation between the points.Also, ma table already include the * 180 / pi() required to do the conversion in degrees so I am saving in computing time. The worst case scenario of error is ±2.8 degrees at +87 and -87 degrees (and this is not likely to be an operation zone). between +75 et -75 degrees the error is very close to 0 so I am happy with this so far. I will come back to the asin() scenario if I eventually need more flash space (requiring to kick out the table).

Thanks

JF Roy