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Ardcore Expander: A4 and A5 to act like A2 and A3?
MUFF WIGGLER Forum Index -> SNAZZY FX  
Author Ardcore Expander: A4 and A5 to act like A2 and A3?
Alwaysnew
Is it possible to assign the same type of funtionality for knobs A4 and A5 as for A2 and A3? The latter two seem to go from 0 to 1023 CCW to CW whereas the knobs A4/A5 seem to be only affected by the input on A4/A5, i.e. not possible to just manually set to e.g. 0.
loss1234
the difference between a2/A3 is that A4 and A5 are not NORMALLED to 5 volts

why? because they provide a very different functionality (and a really nice one)

they are BI POLAR inputs


so whereas inputs A2 And A3 look for a 0-5 input, A4 and A4 can take a waveform which goes from -5v to +5v and convert it into an offset arduino voltage


this is very very useful for the quantizer and the glissando, etc


so their whole setup is different

i hope that helps
Neo
Should we be using analogRead(4) and analogRead(5)? l seem to get strange values with those. l'm feeding +5v into the jacks and getting very big numbers that only change for the first half of each knob's travel. Is this expected behaviour?
AsceticUnderground
Using analogread(4) or 5:
0 volts = 512
+5volts = 1024
-5volts = 0

thats what id expect to see
Neo
That's what I expected but it's not what happens. The big numbers was my mistake. Here's what's happening:

5v in
ccw=521 centre=1023 cw=1023

0v in
ccw=520 centre=520 cw=520

-5v in
ccw=521 centre=0 cw=0

So rotating the knob from centre to cw does nothing, no matter what the input voltage.

Dan, could you explain to a mere mortal with almost zero electrical engineering background what I'm seeing here? Is my expander buggered?
AsceticUnderground
I did exactly what you did above and replicated your results, so this is how the expander is meant to work i would presume.

I always thought that the knobs were basically attenuators, but you have to work with the assumption that 512 is your 0 because its the effective middle value of a bipolar signal that has had a bias of 512 (half of 1024) added to it to keep it within a positive range.

What i did find though looking at this more closely now was that with the knob at 12 o clock i could sweep the range with a +-5v input, however when i put the knob fully cw i could sweep the whole range with an input between roughly +-3.3v
loss1234
yes... you do want to use analogRead (4) and (5)

compare putting a -5v/+5v input in

these are optimized for bipolar inputs

as such you may have to adjust the knob when using
0-5v inputs

there is nothing wrong with your expander


ill try to get an example up soon
loss1234
The knob is just an attenuator. Using +-5 will give you full range 0-1023.

Using 0-5 will give you between 511 and 1023.

0V should give ~512.
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