[sdiy] 1v /oct with ADC question

[Gordonjcp]

On Wed, Nov 30, 2016 at 02:10:30PM -0500, Mike HEQX wrote:
> Hi folks,
> 
>  I want to use an ADC to create discreet note values so I am looking
> at an 8bit ADC.
> 
> I only need 6 bits to get to 64 values. ( I really only need 61 of
> those values to make 5 octaves plus 1 )
> 
> I want to scale the voltage across my pot so that I get 1v / oct
> output for cv usage at full scale, and I also need to produce 61
> discreet values from the adc at the same full scale. So it looks
> like I have to do something mathematical, but I know not what do do.

You need to run your 6-bit DAC off 5.333V because that way you will automatically get 1V/octave.

5.333V / 64 = 0.08333V/semitone
0.08333 * 12 = 1V/octave

Build it just like in the DAC section of the TB303.

-- 
Gordonjcp MM0YEQ