IQMath problem

Liu Xiaoyong

Other Parts Discussed in Thread: CONTROLSUITE

Hello,

I have trouble with IQmath working.

_IQ iqTemp1, iqTemp2, iqTemp3, iqTemp4;

iqTemp1= _IQfrac(_IQ(2.3456));
iqTemp2= _IQfrac(_IQ(-2.3456));
iqTemp3= _IQfrac(_IQ(0.3456));
iqTemp4= _IQfrac(_IQ(-0.3456));

and I get the results are

iqTemp1= -0.3456; iqTemp2= 0.3456; iqTemp3= -0.3456; iqTemp4= 0.3456, the mark of the result is opposite. any ideas?

over 11 years ago

0 Gautam Iyer over 11 years ago

Guru 192875 points

Hi Liu,

Did you check this doc out:

1781.IQmath_Quickstart.pdf

Also check this example:

Regards,

Gautam

0 Liu Xiaoyong over 11 years ago in reply to Gautam Iyer

Prodigy 30 points

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

0 Gautam Iyer over 11 years ago in reply to Liu Xiaoyong

Guru 192875 points

the mark of the result is always opposite.

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

Regards,

Gautam

0 Liu Xiaoyong over 11 years ago in reply to Gautam Iyer

Prodigy 30 points

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

Regards,

Liu

0 Gautam Iyer over 11 years ago in reply to Liu Xiaoyong

Guru 192875 points

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)

0 Salvatorre over 10 years ago in reply to Gautam Iyer

Expert 1460 points

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.

0 Vishal_Coelho over 10 years ago in reply to Salvatorre

TI__Mastermind 20850 points

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.

0 Salvatorre over 10 years ago in reply to Vishal_Coelho

Expert 1460 points

Code Composer Version: 6.0.1.00040

Compiler version: TI v6.2.9

Optimization Level 3

Speed vs size tradeoff 5

0 Vishal_Coelho over 10 years ago in reply to Salvatorre

TI__Mastermind 20850 points

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.

0 Salvatorre over 10 years ago in reply to Vishal_Coelho

Expert 1460 points

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"

0 Vishal_Coelho over 10 years ago in reply to Salvatorre

TI__Mastermind 20850 points

You can download the compiler from this link:

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

0 Salvatorre over 10 years ago in reply to Vishal_Coelho

Expert 1460 points

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.

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