Does Studio directly support fractional/fmul?

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madhun
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Posted by madhun: Thu. Sep 3, 2015 - 01:48 PM
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Hi,

 

I will be diving down the rabbit hole of DSP on an MEGA644A. I see it has fractional multiplication capabilities, but can I use them in C?  Or do I have to do it in assembly?  Are there any examples of how to do this?

 

Thanks!

Tim Ressel
Portland, OR
timr@earthling.net

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Tools, Atmel Studio (AVR-related)
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Gold Markclawson
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Posted by clawson: Thu. Sep 3, 2015 - 02:11 PM
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I forget when it was added exactly but sometime from about avr-gcc 4.8 onwards it gained fixed point:

 

https://gcc.gnu.org/wiki/avr-gcc...

 

So if you have 4.8, 4.9 or 5.0 then you should find this supported and "under the hood" I think you are going to find it is implemented using FMUL.

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madhun
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Posted by madhun: Tue. Sep 8, 2015 - 04:09 PM
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I should add that I am using Studio 6 for coding. It would be nice if the compiler supported fixed point variables and operations.

 

--tr

 

Tim Ressel
Portland, OR
timr@earthling.net

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ka7ehk
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Posted by ka7ehk: Tue. Sep 8, 2015 - 06:46 PM
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According to Cliff, it does support fixed point.

 

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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Gold Markclawson
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Posted by clawson: Tue. Sep 8, 2015 - 07:44 PM
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Yup, as Jim says I just told you thta 4.8 onwards has fixed point support. Studio 6.2 has GCC 4.8.1 so you have it.

 

See:

 

https://gcc.gnu.org/onlinedocs/g...

 

You may want to inspect the asm that generates to verify that FMUL etc are in use.

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