Ardcore Expander: A4 and A5 to act like A2 and A3?

Discussion and Support for our Atmospheric Modification Devices.

Moderators: Kent, loss1234

Post Reply
User avatar
Alwaysnew
Wiggling with Experience
Posts: 361
Joined: Thu Feb 23, 2012 8:55 am
Location: Stockholm

Ardcore Expander: A4 and A5 to act like A2 and A3?

Post by Alwaysnew » Mon Oct 28, 2013 9:46 pm

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
Wiggling with Experience
Posts: 304
Joined: Sat Sep 12, 2009 11:29 pm

Post by loss1234 » Fri Nov 15, 2013 11:25 pm

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

User avatar
Neo
Ultra Wiggler
Posts: 900
Joined: Wed Jul 06, 2011 2:22 am
Location: Bogota

Post by Neo » Sun Nov 24, 2013 6:05 am

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?

User avatar
AsceticUnderground
Common Wiggler
Posts: 136
Joined: Sun Nov 25, 2012 9:22 pm
Location: London
Contact:

Post by AsceticUnderground » Sun Nov 24, 2013 9:15 am

Using analogread(4) or 5:
0 volts = 512
+5volts = 1024
-5volts = 0

thats what id expect to see

User avatar
Neo
Ultra Wiggler
Posts: 900
Joined: Wed Jul 06, 2011 2:22 am
Location: Bogota

Post by Neo » Sun Nov 24, 2013 9:40 am

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?

User avatar
AsceticUnderground
Common Wiggler
Posts: 136
Joined: Sun Nov 25, 2012 9:22 pm
Location: London
Contact:

Post by AsceticUnderground » Sun Nov 24, 2013 10:09 am

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
Wiggling with Experience
Posts: 304
Joined: Sat Sep 12, 2009 11:29 pm

Post by loss1234 » Fri Nov 29, 2013 4:08 pm

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
Wiggling with Experience
Posts: 304
Joined: Sat Sep 12, 2009 11:29 pm

Post by loss1234 » Fri Nov 29, 2013 6:17 pm

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.

Post Reply

Return to “SNAZZY FX”