AVR-Chat

On Nov 7, 2009, at 11:46 AM, syberraith wrote:

> I am designing a guitar pedal effect and need a MCU to sample the  
> signal, perform 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.  These would take a significant number instruction cycles  
> to perform.
>
> The function could also be performed with a look up table, which  
> would require significant memory.

How many positions can one put one's foot on the pedal? Surely no more  
than 256. Then you need only 256 pre-calculated entries in your lookup  
table. Even at 32 bits each this is only 1k bytes.

> I would like to have a sample rate as high as possible, 200K samples  
> per second would be the highest desired, with 46K being the absolute  
> lowest required.

Musicians can change the position of their foot faster than 46 kHz? I  
don't know for sure but is a safe bet there is a low pass filter on  
the current input to the effect box.

--
David Kelly N4HHE, dkelly@HiWAAY.net
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Whom computers would destroy, they must first drive mad.