The phase vocoder from the Pd help examples (Audio examples -> I07) does exactly what you are looking for.

You could build the whole stack and use Pd as a backend. There are some javascript libraries that send OSC messages so the frontend could communicate with Pd over OSC. I haven't tried this and don't really know if it works but I'm thinking of trying that for a project.I'll let you know if I succeed (and maybe if I fail too)

I would avoid the Pduino library and write both the Pd patch and the arduino code if you are experiencing glitches. The problems might also be on the hardware side.
To read more than one button per input you can use a multiplexer.
Also you can buy a bigger board, the Arduino Mega has 54 digital pins...
Using more than one Arduino at the same time should be no problem, you can have multiple [comport] objects in your patch that read different devices.

I don't know this firmata, I tried to use an old one a couple of years ago but decided to write the arduino and pd code myself, and now I'm very happy that I did.
In my experience projects done with externals don't age as well as the ones where I know all the code.
What are you trying to do? The ardiuno serial.write and read are not very difficult to use and there is a lot of documentation and examples available online.

Hello,

i´m having truble to make Pd to work at low latency in Ubuntu Studio 12.04.
I get Pd and Jack to work together with my Audio Interface (Alesis IO4) but only at a frames/Period of 1024, which means a latency of 45.2 ms.
As soon as I try to lowe the Frames/period to lower the latency, I get an Audio I/O error from Pd.
I tried to mess around with the oder parameters, but the only one who appears to affect Pd (and the latency) is the Frames/Period.
I also tried to use the configuration explained here: https://help.ubuntu.com/community/HowToJACKConfiguration , but it doesn´t work either.
I really need to get the lowest latency possible, because I work with live instruments and proccesing.

Any thoughts?

Hey,
thank you both for the infos. Sadly neither of the possibilities worked. I have been trying almost everything and can´t get good results.

I also have Pd on windows, and I have tried to make it work there with jack and asio. Under windows, I get Pd and jack to work in with very low latencies (2 ms) but the sound does not come from my USB sound card, but from the laptop speakers. And when using Max/MSP 5 with the exact same configuration everything works just perfect.
It is very frustrating, because I find Pd much better than Max, but in this case I don´t see any other solution as to rewrite the patch in Max.

I hope to find a better solution and be able to work in PD.