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DSP Processor for Real Time FFT Analyzer

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electronic_engineer

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Hi Guys,

I am in a process of choosing a DSP processor for real time FFT analyzer display developement. My frequency range at the moment is 3Khz to 150KHz. I am using a 14 bit A/D converter to digitize my data. I need to perform a 2048-point FFT.

I am looking for a combination of (DSP+Microcontroller) device, actually I am doing modifications in the existing device that use MCU but I need DSP to process FFT algorithm. I need help from seniors who have ever worked on Real Time FFT Analyzer. Please suggest me some processor for my application so that I could start searching around.

Eagerly waiting for helpful reply.

BR,
EE
 

electronic_engineer

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Jayakarthick

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Think of devices like OMAP L137/138 from TI
It has a strong DSP processor and an ARM processor....

It may suit u :D
 

electronic_engineer

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Jayakarthick said:
Think of devices like OMAP L137/138 from TI
It has a strong DSP processor and an ARM processor....

It may suit u :D

Any one worked with DSP processors for FFT algorithm, please help me out :(
 

mowgli

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For what concern FFT processing almost all DSP are able to do this kind of operations, the limits are applications requirements
- real time 2048 pts => choose a processor with a suitable clock rate and memory to manage all samples
- FFT display => check for a processor which has a native support for video interface or has standard interface to support an external video IF chip. In your application I suppose that the MCU is in charge of managing the display and MMI (Man Machine Interface) but I think that you can move all the functions inside one processor. OMAPs includes one MCU and one DSP and potentially could be able to perform both tasks but I am not experienced on that platform.
You should check also the DaVinci family which supports Windows and Linux embedded OS (if you need it) and are able to perform real time video processing so I think that these CPUs are ok for your application.

Check on TI site: there are many information and maybe some application note for OMAP, DaVinci or C6000 DSP families could help you.

Regards
Mowgli
 

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Thanks for your reply.

My application changed a little, now I am not interfacing the display unit but using PC to analyze the data. I thought usage of OMAP series of T Instrument would be waste of money as it has developed for Video Processing Application..

I went through Atmel Diopsis DCP+MCU unit and found it quite useful, please find the link below
(http://www.atmel.com/products/diopsis/overview.asp?family_id=680)

I think DSP clock which is 100 MHz, is quite much to perform 2048 point FFT or even more, what do you say ?

One difficulty I am encountering is that, I couldn't figure out the actual RAM and ROM momory of the device, some time it shows 370 KB SRAM memory of DSP unit but inside datasheet written this way..

1.7 Mbits of On-chip SRAM:
– 16 K x 40-bit Data Memory Locations (6 Memory Accesses per Cycle)
– 8 K x 128-bit Dual Port Program Memory Location, Equivalent to ~50K DSP

Can you please help me out with memory issue ? Also, will it be possible to do anti aliasing filtering befor doing FFT calculation using this device ?

I will appreciate your help.
 

mowgli

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From the Preliminary summary document

Par. 5.3.4 6-port On-Chip Data Memory System
16K*40-bit on-chip memory => means that you can store in Data memory up to 16K floating point elements, hence there is enough space to store internally the 2048 values to be processed by FFT, plus other constants/variables used by the application to perform calculation (e.g. filter coefficients).
If this is not enough you can use external memory but the SW will run slower because of latency in accesses to external RAM.

Par 5.3.7
It is 8K words by 128-bit dual port memory => if your program is implemented by less than 8k instructions (could be more because a single 128 bit op-code could group more than one instruction) it fits entirely in the internal memory and runs at the maximum speed.
If the internal memory is not enough you have to perform caching / paging of the program instructions in the external memory and execution will be slower (how much depends by the efficiency of memory interface and /or DMA used to fetch instructions from an external ROM).
With optimizations and code compression feature the internal memory is rated by ATMEL to store ~50K DSP equivalent instructions.

Regards
Mowgli
 

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