Spin Semiconductor

Hi everyone !

Although I bought my SKRM boards a year ago, I've only just started my foray into programming the FV-1 chip... oh well, blame it on: life, family, and a little fear of failure, maybe ?! (I did jolt down some cool ideas 'though). I do think I've skimmed the whole wealth of knowledge base/forum info, and probably missed something...

A I've read something to the effect of: "a pot reg. value of 51 is approx. 2 hz in a LFO"... is there a graph/table, where values could be looked up? Say: "LFO pot reg. value of 0=0,25 hz, 10=0,6 hz, ... 100=27hz OR Min/Max values (in hz) of LFO are:... for example. An equation, maybe ?

B Likewise, I just can't for the life of me ! figure out an RDFX value (for a specific freq.) of a filter ...any graph/table/equation that could help ? (EDIT: found it ! in "Adjustable shelving filters": x *Fs/2pi. But what if I want say, 12 or maybe 24 db/oct ?

I think it could speed up my understanding of the FV-1...

TIA !

(please pardon my ignorance , I'm an intuitive, self-taught EE... well, more of an unschooled tinkerer, if you will... OK: flunked math, actually ! )

For LFO, see http://www.spinsemi.com/Products/appnot ... N-0001.pdf it has the equation for LFO frequency.

I see you found the knowledge base info. For a higher order filter for 12 or 24 db/octave you will need to study different digital filter structures. A biquad is a typical IIR structure that can give a 2nd order response, see http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt

Hey, thanks Frank !

Actually just found this : LFO "spanning from one cycle every 24 seconds to about 30Hz when clocked with a 32768 crystal" from knowledge base : "Working with the LFOs"...

I'll read through that link & see what I can make up of it... (EDIT: just read some of it: Oh. My. God. )

IRT increasing filter slope: so, just copying a filter code many times over won't cut it, I guess ? (how naïve can I be...)

...say: can we have a look at the codes over at "Free DSP Programs" (I'm thinking of act_xover.spin for maybe a 24db/oct filter snippet example) or are they "not for your eyes/hear only" ?

While cascading 1st order sections will increase the slope it will not give you an actual 2nd or higher order response. It may be OK for what you are doing so give it a try.

Feel free to use the code from the Free DSP Programs area on the Spin site.

Well, err... how do I acces those ? I click, d/l, SpinSemi IDE opens but can't seem to find it anywhere... sorry, such a noob !

Depends on your browser. You want to save them to your computer then open SpinAsm. You may need to right click on them and select to save the file.

When you're using the cho rdal function to read the sin lfo directly, from where to where does the result go?, -1 to 1?, depends on the memory samples used in the initialization?

Yes, +/-1

frank wrote:Yes, +/-1

Thanks!. According to what I read you can only read the SIN LFO?.

Sweetalk wrote:

frank wrote:Yes, +/-1

Thanks!. According to what I read you can only read the SIN LFO?.

You can read the sin or cos value out of either LFO. Just use SIN0, COS0, SIN1 or COS1.