[sdiy] 1v /oct with ADC question

[Mike HEQX]

Gordon,

I understand what you're saying, however the adc will be quantizing the 
voltage to 8 bit resolution so i'll get too many digital steps for the 
true 1v / oct

i'm basically doing a player piano so the binary values are simply 
addressing key switches from 1 to 61

the CV output is a good side effect since the engine of this thing is 
basically an analog sequencer.

So maybe the problem is already solved? I just let the ADC have 64 steps 
even though the player piano will be missing a few notes on the top end 
that the cv out will actually produce.

That may get strange, but I can't see another way to do it.

Mike



On 11/30/2016 3:41 PM, Gordonjcp wrote:
> 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.
>