[sdiy] Tap Tempo LFO

[Eric Brombaugh]

On Dec 9, 2009, at 5:18 AM, Antti Huovilainen wrote:

> On Tue, 8 Dec 2009, Eric Brombaugh wrote:
> 
>> Using a general-purpose MCU to create a clock for a BBD is probably out of the question for most garden-variety processors. While a lot of them have divider-based timing generators built-in, the high-frequency resolution is probably not adequate to support decent timing & frequency control at the rates needed to clock a BBD.
> 
> Here I disagree. A simple VCO is not that hard to do if you stick to V/Hz and disregard linearity. A PLL would also be dead simple to do, too.
> 
> With the VCO you need to build a calibration table and/or adjust the frequency on the fly, but that's hardly rocket science.

Perhaps I need to defend the statement above with a little more detail:

* 'general purpose MCU' means an inexpensive processor with a normal complement of peripherals like low-res ADCs, timers, GPIO, etc. Think a PIC or AVR.

* I thought the OP was talking about creating a BBD clock source without using any other external components - that was my assumption in this first paragraph. Further on I discussed the possibility of adding an external PLL or programmable oscillator.

So I believe we agree - with a simple external oscillator and minimal control it would be possible to create a clock for a BBD using a cheap MCU.

Eric