mantabernd

Thank you for your fast reply.
 
I kinda got it working. I thought it's enough to set the uart speed once but you need to make it on every boot. So I wrote  startscript what sets the uart speed to 1500000 bit/s and it's working without timeouts. 
It's not my goal yet because the AP6212a datasheet says that it's possible to work with 3000000 bit/s. Unfortunately I'm not able to set this speed.
 
 Furthermore Bluteooth audio streaming is not running very stable. I know it from Raspberry Pi with 4.x kernel and it was really easy and smooth. It seems that it's a problem connected to 3.4 kernel.
 
Can you give me any info about how to activate blutooth on 4.x kernel? I already tried to make it work but with 4.x mainline release you don't have this fex file to activate the hardware modules. I got stucked with building a new device tree.  Maybe you can give me some more info about it?
 
Do you know when a 4.x kernel will be officially available for Nano Pi Neo Air?
 
Thanks a lot
Regards
Bernhard