I built a system that uses both UART1 and UART2 for remote control and troubleshooting of devices. The entire system works fine except that I can’t boot the Rock Pi E with a 40 cm cable plugged into UART2 (only connect to GND, Tx, Rx on the RockPiE; the other end of the cable is floating).
I did some troubleshooting and I suspect that since UART2 is also used in the bootloader to interupt the boot process, I suspect that this floating Tx cable causes issues and interrupts the boot process.
I tried changing the bootdelay to 0 using
setenv bootdelay 0
But I get an error that the MMC didn’t respond to voltage change command.
So… is there another way to modify this bootdelay to try to see if it resolves my issue?