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Is there a way to declare and use circular buffers in C/C++ for the Sharc? I tried searching for some clues with no luck other than finding a few macros in macros.h. I remember someone telling me that these were buggy. I saw a few old posts on the subject but they didn't quite enlighten me :-( I suspect there is no way to use the native support of the processor. I'd appreciate examples or pointers to examples/docs that come with the VisualDSP tools. Cheers Bhaskar |
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circular buffers using C/C++
Started by ●March 9, 2001
Reply by ●March 9, 20012001-03-09
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Hi, I had posted the same question long back,two three times. Nobody replied. Even I suspect ADSP tools supporting circular buffer declaration in C. One more similar problem is declaring a variable at absolute address. Could anyone in the group look into these issues ? Regards, Nagaraj CS --- wrote: > Is there a way to declare and use circular buffers > in C/C++ for the > Sharc? I tried searching for some clues with no luck > other than > finding a few macros in macros.h. I remember someone > telling me that > these were buggy. I saw a few old posts on the > subject but they > didn't quite enlighten me :-( > > I suspect there is no way to use the native support > of the processor. > > I'd appreciate examples or pointers to examples/docs > that come with > the VisualDSP tools. > > Cheers > Bhaskar > > _____________________________________ > Note: If you do a simple "reply" with your email > client, only the author of this message will receive > your answer. You need to do a "reply all" if you > want your answer to be distributed to the entire > group. > > _____________________________________ > About this discussion group: > > To Join: Send an email to > To Post: Send an email to > > To Leave: Send an email to > Archives: http://www.egroups.com/group/adsp > > Other Groups: http://www.dsprelated.com > ">http://docs.yahoo.com/info/terms/ __________________________________________________ |
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Reply by ●March 9, 20012001-03-09
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I never used them, but I believe the old (GNU-based) ADI C compiler had built-in compiler functions that allowed the use of the hardware circular buffers. They directly used specific DAG registers, so they were a bit difficult to use. I think these went away when ADI changed to VDSP. I have always just used the modulus operator in C to implement my circular buffers. This can be a time-consuming operation if you are running on a fixed-point DSP. If you use a buffer length that is a power of 2, you can mask off the upper bits to achieve a faster modulus computation. For example, if you want to increment your circular buffer pointer for a buffer of length 8, you can do: index = (++index) % 8; which is equivalent to: index = (++index) & 0x07; If the compiler is good, it will compile the first statement the same as the second statment. If not, then the second statement will definately run faster, especially on a fixed-point processor. Hope this helps. -Derek ----- Original Message ----- From: nagaraj cs <> To: <> Cc: <> Sent: Thursday, March 08, 2001 10:09 PM Subject: Re: [adsp] circular buffers using C/C++ Hi, I had posted the same question long back,two three times. Nobody replied. Even I suspect ADSP tools supporting circular buffer declaration in C. One more similar problem is declaring a variable at absolute address. Could anyone in the group look into these issues ? Regards, Nagaraj CS --- wrote: > Is there a way to declare and use circular buffers > in C/C++ for the > Sharc? I tried searching for some clues with no luck > other than > finding a few macros in macros.h. I remember someone > telling me that > these were buggy. I saw a few old posts on the > subject but they > didn't quite enlighten me :-( > > I suspect there is no way to use the native support > of the processor. > > I'd appreciate examples or pointers to examples/docs > that come with > the VisualDSP tools. > > Cheers > Bhaskar > > _____________________________________ > Note: If you do a simple "reply" with your email > client, only the author of this message will receive > your answer. You need to do a "reply all" if you > want your answer to be distributed to the entire > group. > > _____________________________________ > About this discussion group: > > To Join: Send an email to > To Post: Send an email to > > To Leave: Send an email to > Archives: http://www.egroups.com/group/adsp > > Other Groups: http://www.dsprelated.com > ">http://docs.yahoo.com/info/terms/ __________________________________________________ _____________________________________ Note: If you do a simple "reply" with your email client, only the author of this message will receive your answer. You need to do a "reply all" if you want your answer to be distributed to the entire group. _____________________________________ About this discussion group: To Join: Send an email to To Post: Send an email to To Leave: Send an email to Archives: http://www.egroups.com/group/adsp Other Groups: http://www.dsprelated.com ">http://docs.yahoo.com/info/terms/ |
Reply by ●March 9, 20012001-03-09
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On Thu, 8 Mar 2001 19:09:05 -0800 (PST), nagaraj cs wrote: > One more similar problem is declaring a variable at absolute address. This one's not too difficult, with some macro magic. Just declare the variable like this: #define my_absolute_object (* (my_absolute_object_type*) 0x123456) You could also declare the address in the LDF file and then declare it extern in the C file: // in LDF file output section // (You'll have to experiment with this to get the syntax and offsets right.) _my_absolute_object = 0x12345; // in C file extern my_absolute_object_type my_absolute_object; |
Reply by ●March 9, 20012001-03-09
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> similar problem is declaring a variable at absolute > address. Another way to do this (other than the macro trick that Ken suggested) is to declare a single word segment in your ldf file at the abolute address you want and then use the placement support of the compiler. So if you want a variable at address 0xC000 then create a segment called my_var_seg in the ldf file which is located at this address and is only 1 word (or however long your variable is) long. Then in your C code you can declare the variable like this... static segment("my_var_seg") int my_var; I think the macro works better with regards to ease of changes and maintenance. Cheers Bhaskar --- In adsp@y..., nagaraj cs <nagaraj_c_s@y...> wrote: > Hi, > I had posted the same question long back,two three > times. Nobody replied. Even I suspect ADSP tools > supporting circular buffer declaration in C. One more > similar problem is declaring a variable at absolute > address. > Could anyone in the group look into these issues ? > > Regards, > Nagaraj CS > > --- bhaskar_thiagarajan@y... wrote: > > Is there a way to declare and use circular buffers > > in C/C++ for the > > Sharc? I tried searching for some clues with no luck > > other than > > finding a few macros in macros.h. I remember someone > > telling me that > > these were buggy. I saw a few old posts on the > > subject but they > > didn't quite enlighten me :-( > > > > I suspect there is no way to use the native support > > of the processor. > > > > I'd appreciate examples or pointers to examples/docs > > that come with > > the VisualDSP tools. > > > > Cheers > > Bhaskar > > > > > > > > _____________________________________ > > Note: If you do a simple "reply" with your email > > client, only the author of this message will receive > > your answer. You need to do a "reply all" if you > > want your answer to be distributed to the entire > > group. > > > > _____________________________________ > > About this discussion group: > > > > To Join: Send an email to > > > > > > To Post: Send an email to > > > > To Leave: Send an email to > > > > > > Archives: http://www.egroups.com/group/adsp > > > > Other Groups: http://www.dsprelated.com > > > > > > ">http://docs.yahoo.com/info/terms/ > > > > __________________________________________________ > |
