TB-303 BPM tempo controll

[Byron G. Jacquot]

>No, the frequency counter will not influence the 303, only read the clock
>pulse.
>Things will be different if you let the frequency counter or uC drive the
>303.
>However the 303 timing may be quite stable anyway (it is a uC clock isn't
>it?).

No, the tempo clock in the 303 is a pair of inverters and an R/C network.
It's not a uC timer...with several advantages/disadvantages:

Being out of the micro, it's easy to find it's pulse output to run to other
devices...or easy to remove that clock and substitute an external one.
Since it's an analog RC network, there aren't any ugly issues with the
granularity of possible tempos (it is a 4-bit micro, after all!).

However, it might also have some jitter...though not an incredible amount,
possibly enough to help account for some of the "Feel" of the TB303 sequencer.

There are a couple ways to solve this problem, either would use a
microcontroller...one is to use an "input capture" timer, and monitor the
clock coming off that oscillator, do some math to it, and turn that into
values on 7-segment displays.

The other way would be to replace the internal timer completely, and build a
little DIN-sync generator box using an "output compare" timer, that outputs
master clock and other DIN signals and displays the BPM.  Wouldn't take much
tomake it do MIDI clock as well.

(but can't you find a Roland MSQ-100 or 700 to do the same as well?)

Byron Jacquot