[sdiy] "lunetta"/CMOS sound-making equivalents in C Programming???

[Tom Wiltshire]

One other possibility that no-one has mentioned is to use a variable clock for the micro. The PICs can be clocked anywhere between 20MHz and virtually DC. So you can set up some routine in code that produces your waveform or dividers or whatever, and then feed a basic squarewave VCO into the chip to clock it. That way, you avoid the aliasing, you get to add CV control of the rate, etcetc. This would be great for staircase waveforms and such like. Since power consumption is related to uP clock speed, it should use next to no juice too.

Just a thought. I've never tried it, but it's always seemed like a solution looking for a problem.

Tom


On 23 Mar 2012, at 15:05, nvawter at media.mit.edu wrote:

> 
> yes, definitely.  although, many simple CMOS logic tasks on microcontrollers, such as dividers, can run decently fast, e.g. around 100-500 kHz.
> 
> Another thing worth considering might be to dither and/or randomize the sample rate.  sound crazy?  sure is!  but it would distribute the noise floor a bit more equitably.
> 
> alternatively, external signals can trigger interrupts in the micro to execute the computations.  while that adds some overhead, for some classes of processing, it will curtail aliasing.
> 
> -Noah
> 
> 
> Quoting Olivier Gillet <ol.gillet at gmail.com>:
> 
>> Keep in mind that by doing this CMOS emulation stuff in code on a
>> micro, you'll have to decide on the time base (sample rate) at which
>> you refresh your variables ; and you'll get nasty aliasing problems
>> unless you work at a very high sample rate.
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