Beware that analogue inputs (can) have noise (they fluctuate a little). 
The analogRead() command converts the input voltage range, 0 to 5 volts, to a digital value between 0 and 1023.

If you can settle with 12 inputs the Uno will suffice:
http://arduino.cc/en/Main/ArduinoBoardUno


p.s.: Multiplexing/de-multiplexing is the ability of addressing (or conversely be addressed) of several outputs with fewer inputs. You have chips that do that, example with 3 binary digits you can multiplex to 8 outputs, with 000 being the first, 001 the second, etc,.. up to the 111, which would be the 8th. People also call it MUX and DEMUX.

On Sun, Apr 10, 2011 at 2:44 PM, Pierre Massat <pimassat@gmail.com> wrote:
Hi Pedro, thank you for this quick response.
- Yes, size does matter, because it all needs to fit in a stombox. But the boards don't seem to be to large anyway...
- Price matters too (i'm not gonna buy the one at at 130 or something).
- What is multiplex? I need something like 12 simple switches (digital inputs??), and maybe 3 or 4 analog inputs (i v'e read on their website that one can have up to 6, is that right?). The only thing that really matters concerning the analog inputs is the "resolution". I just read somwhere on their website that one board outputs integers from 0 to a little more than 1000 for it's analog inputs. If this is true, this would mean than i would get a resolution that's a little less than 10 times higher than that of my gamepad. But there seems to be different boards with different a difference resolution (i'm assuming it's 8, 16 or 32 bit, am i right?). I don't know if i can order any pre-assembled model with any board.

I also saw that the board could power LEDs. This could be very interesting, because i'm going to assign a switch to the connection of the expression pedal (analog) with certain parts of my patch. So for instance at startup the pedal controls effect 1, and if i push the button i goes to effect 2, etc., and only goes back to effect 1 after it's reached the last pedal-controlled effect. So it'd be nice to have one LED for each effect on my stompbox so that i know exactly which one is currently controlled by the pedal. Do you think I could program this easily?

Pierre

2011/4/10 Pedro Lopes <pedro.lopes@ist.utl.pt>
They have a lot of models (not accounting for spin-offs done by other folks, which some are great - long live open hardware), I think there are some more parameters for choosing an arduino model:
- Does size matters? 
- Does price matters?
- 8 buttons + 1 potentiometer (in a pedal). Extendability up to 12. 
  - do you wanna multiplex[1], or simple coding?

 Maybe if you really want a lot of inputs, Duemillianuove will not suffice, and maybe Mega is the way to go, but its more expensive and bigger. 

[1] http://www.arduino.cc/playground/Learning/4051

On Sun, Apr 10, 2011 at 2:14 PM, Pierre Massat <pimassat@gmail.com> wrote:
Hi all,
I sorry to start yet another thread about arduino, but i'm too lazy to search the archives and i suppose that they are upgrading the different models frequently.
I have been using a hacked gamepad-turned-stompbox to control my live patches, and right now i feel that it's time to build something else that would suit my needs more closely.
I have to choose between a decent gamepad that i could hack and a arduino board. Only, i don't know anything about arduino. So it'd be nice if a list member could help me a little bit.
Here's what i have right now :
- 8 buttons + 1 potentiometer (in a pedal).
I'd like to have more buttons (I could have 12 using the game controller, can i have more with a arduino board?). And it'd be nice if could have more "analog" pots (i could have up to 4 using the gamepad, but they're hard to solder...).
Also, i'd like to know the "resolution" of the analog inputs of a arduino board. Is it higher than that of a gamepad? That'd be cool because i could have a smoother control over certain values in my patch.

And finally, what do i need to connect the arduino board to Pd? Is it the HID object or something different?

Any help welcome.

Cheers!

Pierre

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--
Pedro Lopes (MSc)
contact: pedro.lopes@ist.utl.pt
website: http://web.ist.utl.pt/Pedro.Lopes / http://pedrolopesresearch.wordpress.com/ | http://twitter.com/plopesresearch




--
Pedro Lopes (MSc)
contact: pedro.lopes@ist.utl.pt
website: http://web.ist.utl.pt/Pedro.Lopes / http://pedrolopesresearch.wordpress.com/ | http://twitter.com/plopesresearch