Id like to transfer audio rate signals in the 0..5v range into/out of Axoloti.
e.g. imagine say an oscillator as output, or feeding a audio signal 0..5v into to drive a env follower.
( 2 channels in and out is fine for now, I'm after a simple solution )
and wondered if anyone can point me in the right direction:
I see 2 options:
A) GPIO, this is 0. 3.3v, ive got a fair idea how to scale this to 0..5v.
has the advantage i can take as many channels as there are analog gpio. (and could multiplex for more, albeit reducing SR)
BUT, I see 2 issues
i) i think currently we can only drive gpio at k-rate, so I'm guessing id need to modify firmware? ive not looked yet, so this is just a 'feasible' or not question... will it have significant cpu impact due to extra io.
ii) i write an audio rate gpio in/out which i use instead of audio out, then use this in my patches,
pain to differentiate patches, but its ok.
will there be aliasing issues? as I don't have the codec which I suspect has anti aliasing filters?
B) take audio in/out RTS and scale the -1.3.. +1.3v to 0..5v, centred around 2.5v
no idea how to do this, i assume i need opamps, but cant find an obvious reference.
output is just adding +2.5, and amplifying by ~ 2xm no idea how to do this
input, reduce by 2.5v, and scale by half, again no idea
I'm assuming the codec wont allow me to just input/output 0...1.3v ? ie. do it in software?
also id be a bit concerned id send in a bit too much voltage, can cause damage.
(though I'd assume the audio input is protected to a higher peak to peak voltage, and will just clip?)
thanks for any pointers
another side note...
i see the midi/power part of the board has 0..5v where it connects to the main part, if i chop off the part, can i use this to power axo from 0..5v?
(what would i need to do do disable usb , i.e. what do i connect to vbusend)
... its not a major thing, i can connect a 9v to barrel, but a bit tidier to drive it from 5v.