ReSpeaker Core V2.0 custom u-boot without serial port / menu


my ReSpeaker Core V2.0 is connected to an Arduino via 3v3 serial connection (TX/RX/GND). The Arduino cyclically sends sensor readings and accepts messages from the respeaker.
There are two problems in this setting:

  1. If respeaker reboots, uboot catches the data from arduino, interpretes it as a keystroke and enters boot menu (Press any key to interrupt boot…) where it is stuck forever
  2. Arduino gets disturbed by uBoot messages as well as kernel output

Can you please give some guidance how you built u-boot?
Did you have a board file at hand? Dito for other needed files, like devicetree.
Any Repo with the forked DENX code?
I only plan to boot from SD Card - no eMMC, so no bricking :wink:

Any hints on the proper settings for disabling uboot menu - found a variable “silent” - so at least one half of Problem 2 is solved - already found kernel arguments passing serial port for logging and uboot setting for serial device addresses - any chances to set something there like /dev/null in linux?
Is this git a good starting point?

Thanks and best regards