IQMath problem

Hi Liu,

Did you check this doc out:

1781.IQmath_Quickstart.pdf

Also check this example:

Regards,

Gautam

Hi Gautam,

Thanks for your suggestion. Yes, I had check the example, But I can not get the same result, the mark of the result  is always opposite.

Regards,

Liu

 the mark of the result  is always opposite.

That's very strange, Liu. Did you try with _IQxfrac like _IQ24frac?

Regards,

Gautam

I test the _IQ15frac, the mark of result is opposite. but the _IQint function is correct .

Regards,

Liu

After researching a lot here's what I concluded:

This is not an error, there is a misunderstanding of how the functions work.

Here's an example:

-2.3456 when rounded down (truncated) to the integer portion is -3.0.  The fraction is .6544.  When you add -3.0 to .6544 you get -2.3456 .

This is because IQmath does not use floating point numbers, but uses fixed point numbers, and simple fixed point operations.

Check accordingly and revert.

Regards,

Gautam

(Note: The above extract has been taken from http://e2e.ti.com/support/microcontrollers/stellaris_arm/f/471/p/176794/1045860.aspx)

Gautam,

I discovered the same issue as Lui. There is an error. Example 1 from the IQMath Library v1.6.0 doesn't yield the same results in the processor. However TI wants to define it, it needs to be consistent with the documentation.

Hi,

I have tried the example cited in the documentation and it works fine. I am unable to reproduce the issue. Can you specify the build settings e.g. CGT version, compiler options - optimization etc.

Code Composer Version: 6.0.1.00040

Compiler version: TI v6.2.9

Optimization Level 3

Speed vs size tradeoff 5

Hmm i wonder if this is a CGT issue, I tried with compiler tools v6.4.0 with -O3 and -opt_for_speed=5 (GLOBAL_Q=24) and it works fine. Also im using IQMath lib v160.

Could you update the compiler to 6.4.0 and try again.

The best I can do is 6.2.10 (same results). I checked for updates, but I don't have the option to upgrade to 6.4.0.

I am also using the IQMath Library v160.
"C:\ti\controlSUITE\libs\math\IQmath\v160\include"

You can download the compiler from this link:

http://software-dl.ti.com/codegen/non-esd/downloads/download.htm#C2000

I figured out the problem after adding the latest compiler. It helped to point to the issue.

1. I was using the wrong compiler include: "C:\ti\ccsv5\tools\compiler\c2000_6.1.7\include" while using compiler 6.2.10

2. I was using the wrong IQMath.Lib resource file. My include is C:ti/controlSUITE/libs/math/IQmath/v160/include, but I was using c:\tidcs\DMC\c28\v32x\lib\dmclib\cIQmath\lib\IQmath.lib instead of C:\ti\controlSUITE\libs\math\IQmath\v160\lib\IQmath.lib.

Note: When I switched to 6.4.1, my project no longer fits. I'm sticking with 6.2.10.