Re: fixed point digital low pass filters

Jan 06, 2008 0 Replies


>> to generate code for a first order Butterworth floating point


> >> The input values to the filters are fixed point 16bit ADC values.
> >> low pass filter with 250kHz sampling frequency, and a 100kHz corner
> >> frequency. This would require a DSP to run on, since I need 6 of
> > these
> > Probably even MSP430 or 68HCS12 could be sufficient.
>
> IIRC both of these processors top out at about 40MHz clock speed. So
> you're saying he can run six second-order, 32-bit precision filters in
> 160 clock ticks on a 16-bit processor?

Where did the second order and 32 bit precision come from? What I said that it could be possible to fit six first order filters @ 16 bits @ 250kHz into HCS12 or MSP430.


Interesting.

"If you give me $1000, I will do it much better and more efficiently" (tm)


>> Can I convert the floating point code to fixed point?
> > It is certainly possible, however I don't know if you can :)
>
> One can make this conversion with proper guidance; I don't know if anyone
> could with Vladimir as his only source of information.

Wasn't that an exact answer to the question asked?


>> Here's the floating point code that mkfilter generates:
> > [...]
> > What a horrid code.
>
> And thank you for increasing world knowledge by saying why.

I certainly kneel before the prophets who can preach about 2 x 2 = 4, and who can say a lot without telling anything.


VLV


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