[sdiy] Digital modular backplane - update

Paul Maddox yo at VacoLoco.net
Mon Mar 31 23:26:38 CEST 2014

You could also use a 'snap' mode (I think some waldorf synths do this)

I do this on gorf (optional mode you can turn on/off)

In gorf if the velocity of a step is say 50% and the knob is at 75% then 
as you turn it the value doesn't suddenly jump as it would in example C 
(which I personally have no problem with).
instead it shows "hi" as the knob is higher than the value it's 
changing, so you keep turning it, when you get the to value it 'snaps' 
and at THAT point the knob starts changing the parameter.
Similarly if the knob is at 25%, with the value at 50% it shows "lo".

you could replace "Hi" and "Lo" with a red/green LED. heck even one 
inside the pot shaft.

Rotary encoders aren't that hard to implement, nor a simple LED ring. 
and given the front panel is going to need some sort of micro it could 
handle the LEDs and encoders without much effort.
If there's space in the FPGA (someone mentioned using an FPGA) then why 
not grab one of the many FPGA CPU Cores that are free online and use 
that to run the front panel LEDs/Encoders.

the touch screen idea is a valid one also, I mean why not, LCDs are 
relatively cheap and touch screens can be had for a few pennies more 
(check ebay).

I'm NOT quite so convinced about the iPhone thing though, you *could* 
make it work using the contactless thing, but you'd need to keep moving 
the iPhone, or buy a lot of them :)


On 31/03/2014 12:53, Roman Sowa wrote:
> W dniu 2014-03-31 10:59, John Slee pisze:
>> (a) motorised pots/faders (do these introduce a bunch of noise?), or
>> (b) encoder + digital pot + some kind of position indicator (LEDs?)
>> (c) ordinary pots and no "balancing" as you describe it, a la Roland
>> Jupiter and probably countless other analog synths
>> Of these, (a) and (b) are going to be expensive (relative to decent
>> quality ordinary pots), (b) will require a more complicated design, and
>> (c) is just plain awful.
> and there's also pot ala Poly6. When you reach top of the knob, and 
> still wish to go higher, you have to first turn it down, to push down 
> the virtual range. I don't know if it sounds clear. It's a bit anoying 
> when you have to pump the value quickly down for a moment, but 
> guaranteed no sudden jumps with touch of the knob.
> For me the best choice is no-detent high resolution encoder with at 
> least 30 tiny LEDs around. Far from being cheap or affordable.
>> And then you have other inputs, such as toggle/rotary switches. I
>> suppose you could replace those with momentary buttons and some
>> kind of indicator. I'd prefer that most of the time actually.
> I like the irreplaceable feel of flat lever toggle switch, but on the 
> other hand nice pushbutton with maximum 4 LEDs around indicating 
> current state is just as much appealing
> and now the time for a very stupid joke, please don't ban me for this:
> why not use touchscreen displays for entire module panels and forget 
> about all the knob-related problems? Or simply make special brackets 
> for iphone to match rack rails, put a few dozens of those in, and 
> voila, modular synth of our times...
> Roman
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