Spin Semiconductor

Hello out there, and firstly: CONGRATULATIONs on providing this fine chip!

3 simple questions from someone who hasn`t dug into the programming side of the FV-1 yet,
but for now is looking at the "black box" as a quasi-analog component:

what is the resolution of the ADC (or ADCs)
at the POT pins 20 to 22 ?;

at which repeat-rate are the voltages being read?;

and are they being read simultaneously by 3 ADCs,
or (sequentially) multiplexed by 1 ADC.

Thank You for any feedback
(no pun intended)

kindest regards,
Ton / "puretube".

9-bit resolution on the POTS

While they are updated at Fs, there is some internal filtering of the pot causing it to have about a 100mS time constant.

Each POTX has it's own ADC, not multiplexed

thanks!

Hi Frank,

Could you share more details on the 9-bit adcs for the pots and their filtering?

Specifically, could you say more about the implementation and\or characteristics of the "about 100ms time constant" filtering ?

Also, any other info pertinent to applying one of the POT inputs as a dynamically-varying CV input (as in an analog envelope signal input where 9-bits and a 100 ms TC might be quite adequate) ?

Thanks,

mr coffee

They are pretty basic ADCs. They have some filtering and hysteresis in them to provide a stable value out. As this filtering and hystersis block is clocked it results in a 125mS time constant at 32KHz sample rate.

I would need to talk to Keith to get more detail on the circuit if you need it.

mr coffee wrote:
Also, any other info pertinent to applying one of the POT inputs as a dynamically-varying CV input (as in an analog envelope signal input where 9-bits and a 100 ms TC might be quite adequate) ?

You know you can just use the values for adcl and adcr for extracting envelopes, right? If you need an additional CV input, you can use one of the audio inputs, assuming you don't need stereo in. Instead of tying up a POT parameter for a simple envelope control, you can just use the value of adcl or adcr as the instantaneous value for your envelope detector. There's a limiter program that covers this pretty well, and you can snag some of that code for use in controlling an LFO or other parameter.

Like I said, if you need a dedicated external input (like a compressor sidechain,) you can use the other analog input. If you want to actually use a DC voltage, you'd want to use the POT pins, since the analog inputs are AC-coupled.

One last thing - if you're changing the POT inputs quickly, you might want to put in some smoothing code to prevent "zipper" noises when ramping them up or down. I had some issues with this, using a POT to control my delay times, and with the smoothing code it works in a much less "digital-sounding" way, if that makes sense.
Substitute whatever POT you're using for pot2.

Matt Farrow