USB audio + touchscreen problem

[ArthurJam]

Hello,

I need help for my personnal project.
I have a raspberry pi 2 with a USB soundcard in order to get a better sound compare to onboard sound output.
But if i use a touchscreen ( like this one : http://www.wvshare.com/product/3.5inch-RPi-LCD-A.htm ), i cant have a clear sound.
I hear pop and crack. To avoid this, i need to run a lower value of txbuflen on the screen. I found this solution thanks to this issue : https://github.com/raspberrypi/linux/issues/971
But this solution slows down dramatically the refresh of the screen.

Notro (a contributor to fbtft driver) says :

It's probably a buffer underun in the usb audio device. But I know to little about the processor internals to say anything about where the bottleneck is

Someone have a idea to avoid this ?

Sorry for my poor english.
I will appreciate any help.
Thx.

[ArthurJam]

Hello,

When I play a sound on my usb card, the screentouch is really laggy.
Do The raspberry can have two periphericals in live use ?
My screentouch use RPI.

Thanks