RockPi4 won't restart or boot when UART2 is used (Console reconfigured already) and receives bytes on RX (GPIO header Pin 10) - Need a U-boot that requires atypical and specific keypress to stop Autoboot

[gpread]

U-boot defaults to "In: serial" and also listens for packets (its assumed that its a keyboard/terminal) so that a keypress can stop autoboot.

I am successfully using /dev/ttyS2 after modifying /boot/armbianEnv.txt (Console=Display) and masking the gettyS2 service. The device/system I have connected to UART2 (/dev/ttyS2) periodically sends bytes.
 

Thus, if a remote restart or a cold boot is performed (power glitch or power reset) while that system is connected to UART2, it triggers the abort of Autoboot. Requiring the other system/device to be disconnected from UART2, a cold boot of the RockPi4 and then reconnection of the system/device to UART2.

 

I don't see any standard way to reconfigure things to avoid use of UART2 during U-boot and of course its useful for dealing with real issues to be able to interrupt autoboot and then interactively control what happens.

 

Hence the best solution I can see would be for there to be a change to the armbian u-boot to look for a specific key or key sequence rather than just any old key/byte that hits the UART2 RX.

Perhaps there could even be a parameter added for use in armbianEnv.txt that allows the abort Autoboot key or key sequence to be defined/redefined ?

Thanks for any/all assistance