Rhythm generator

[Curtin, Steven D (Steven)]

Hello WJ,

This sounds very similar to what I've been doing with programmable logic.  I
have a Philips PLD that counts down from a master clock which is a 555.
This clock can also be adjusted by hand for tempo changes.  The PLD can also
be programmed to have touch-switches enable and disable each of the counts.
If you add together a bunch of these pulses and run each through a variable
attenuator you have the basics of the Blacet "Digital Pattern Generator".
I've run out of gates and pins with the PLD and am migrating the design to a
Lucent FPGA.  The eventual idea is to have a Serge touch keyboard I have
flip between different "pages" of AND and OR gates for different pulse
combinations.  I just have the pad PCB for the Serge TKB, none of the
electronics, since that can all be done with the gates in the FPGA.  I have
a design for doing this which was prototyped on the PLD before I ran out of
logic on that chip.  Let me know if this would help you out.  I'm not
planning on making a product out of this or anything, but I am planning to
publish the design and make it easy for other people to replicate.  I have
to clear this with the Lucent IP department but they're pretty reasonable
about this sort of thing- it's not an active market for them.

Steve C

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Steven Curtin  
Lucent Technologies Microelectronics
ph: (732)957-2996   fax: (732)957-6878
http://www.emf.org/subscribers/curtin/
sdcurtin at lucent.com
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> ----------
> 
> The first idea I had was:
> Generate a square-wave (e.g. using a 555 timer) at frequency f.
> Put this through a counter to generate square-waves at frequencies
> f/2, f/4, f/8, f/16, etc.  8 bit counters are widely available, giving
> me all frequencies from f to f/128.
> Now for each drum sound, select some of these square-waves and
> perform a logic AND on them.  Use the result as the trigger for that
> drum sound.
> e.g.  I select f, f/4 and f/16 for the bass drum.  Take the logical
> AND of these three waves and use it for the trigger line of the bass
> drum (If you're having trouble following this, try drawing a graph of
> the function f AND f/4 AND f/16).  The bass drum triggers whenever
> this function rises from logic 0 to logic 1.
>