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The Filter Wizard Blog
Aug 18, 2012

I just posted another contribution to the PSoCaMorph project, the VCF: http://www.elektor-projects.com/contribution/psocamorph-architecture-3-the-vcf.12424.html.  OK, most of the components are not actually in a PSoC, but one of the PSoCs in the system will have its work cut out providing all the control signals.  For this project, I didn't want to use the DFB to do the waveform synthesis and "filtering without filtering" stuff.  I'd much rather use it to do some of the other effects, like chorus and reverb.  Ah, I suppose that means I'd better work out how to do that, then <g>.  Keep sending in all those comments and questions!  best / Kendall

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Aug 13, 2012

The second Filter Wizard article on waveform synthesis schemes for the DFB is up on EE Times Europe now: http://www.analog-eetimes.com/en/more-direct-waveform-synthesis-mr-chebychev-helps-out.html?cmp_id=71&news_id=222903800.  In the article I mention polynomial evaluation stuff in passing, before using an alternative method.  But for quite a few applications, the DFB can be a good engine for rapid calculation of polynomials using Horner's method.  Provided the error bounds imposed by 24bit fixed-point arithmetic are appropriate, this is way faster than doing it in a CPU.  The iterative method is reminiscent of FIR filter execution and leverages the addressing ability of the DFB hardware.  In the end, for the music synthesis task, I opted for... but why give it away - go check out the article!  best / Kendall

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Tags: PSoC® 3
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Aug 06, 2012

Thanks to your votes (OK, and also to my design contributions <g>) the PSoCaMorph has been upgraded to "in progress" at http://www.elektor-projects.com/projects.  Still need people to start building these circuits and to address some of the practical physical issues.  Spend a lot of time over the weekend looking at aspects of the Voltage Controlled Filter.  Lots of external components, so it's going to need a dedicated circuit board.  Time to hit the Rolodex!  Keep the comments coming in.  best / Kendall

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Aug 03, 2012

Just posted the next architecture installment over at the PSoCaMorph project page at http://www.elektor-projects.com/contribution/psocamorph-architecture-2-v-to-i-and-cco-core.12398.html.  I reckon that the basic VCO/CCO design could be very useful in a range of PSoC projects.  If all goes according to plan, the discharge reset time shouldn't be a factor in the voltage-frequency relationship.  I'll be interested to see just how fast it will run and how linear it is - it's another way to make a PLL FM demodulator, if it's linear enough.  Remember, check it out and vote for it.  There are some dev kits on offer for people who are serious about participating.  Next piece - the voltage-controlled filter.  I'm trembling with excitement myself, so goodness knows how you are all feeling  (-8b  best / Kendall

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Jul 31, 2012

I uploaded the first tranche of technical thinking about PSoCaMorph to the website http://www.elektor-projects.com/project/the-psocamorph.12269.html so you can now go and check that out.  Soon I'll put a description of the planned VCO core - it should be useful for other applications too.  After that comes the bit you (well some of you) have all been waiting for - the Voltage Controlled Filter.  OK, it's going to have quite a few external components because PSoC wasn't designed to do these continuously-controlled tasks.  But if you want to make a real oscillator and filter rather than do it all in the digital domain (next Filter Wizard on that out soon, by the way), this should be a good way to go.  I suspect that once the oscillator signal is filtered, though, we'll want to get into the digital domain.  That will happen through PSoC's delta-sigma ADC.  After that... well, I've started mulling over how one would do a credible chorus effect, to make it sound like you're using multiple not-quite-synchronized oscillators.  I think that's going to work better than making multiple actual oscillators, and trying to stop them locking to each other in ways you can't control.  There are some dev kits up for grabs for those of you that really do want to participate and contribute.  Probably a beer or two too, for those of you that actually get these circuits working and (a) can demonstrate them and (b) live somewhere I can get to easily!  best / Kendall

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