AVR-Chat

--- In AVR-Chat@yahoogroups.com, BobGardner@... wrote:
>
> Guitar amps aint real hifi. The speakers dont get much above 3.5KHz, so I think a 20MHz AVR might do a respectable job of a 10bit 9KHz transfer table lookup function and echo chorus type effects. 
> 
> 
> -----Original Message-----
> From: syberraith <syberraith@...>
> To: AVR-Chat@yahoogroups.com
> Sent: Sat, Nov 7, 2009 12:46 pm
> Subject: [AVR-Chat] Looking for the Right AVR for my Project
> 
> 
> 
> I am designing a guitar pedal effect and need a MCU to sample the signal, 
> erform a non-linear function, then generate a control current.
> The project requires one ADC and one DAC these can be separate devices.  
> The non-linear function can be performed without a FPU using CORDIC routines.  
> hese would take a significant number instruction cycles to perform.  
> The function could also be performed with a look up table, which would require 
> ignificant memory.
> I would like to have a sample rate as high as possible, 200K samples per second 
> ould be the highest desired, with 46K being the absolute lowest required.  
> I have been looking at 16 bit devices in the 30 MIPS range and up.  Most of the 
> nes I have seen with sufficient speed have been excessive elaborate.
> So, does anybody know on a simple device with enough speed for my project?
> Regards,
> Fred 
> 
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I see I need to clarify some things.

This is a compression only effect,  It has two states, on an off.  The lookup table would be for a transcendental function, which could also be done with a iterative process that would take up less memory but more instruction cycles.

Yes, dsPICs look promising.  I've been looking at PIC30s and PIC33s, which run at up around 30MHz.  The trouble with them is that they come with a lot of communication peripherals that I lack any need for such as Ethernet or USB etc.  The basic MCU for those is a PIC24 that I think only runs at 16MHz.

I could just as well use a 32 bit device.  Lots of AVR models there with the the same selection problem. 

Being new to MCU and out of practice with coding.  I do need to look at what's been done before in similar projects.

Thanks,

Fred