After the Jetson TX2 NX serial port opens UART1, it cannot be powered on after shorting RXD-TXD and CTS-RTS in RS232 mode

Hi!
After using TX2NX, in order to adapt to our custom backplane, after opening UART1, after shorting RXD-TXD and CTS-RTS in RS232 mode, the system is stuck in the NVIDIA interface and cannot enter the system; if the RXD-TXD and CTS-RTS are disconnected, they can enter the system smoothly. Where do I need to change it? Thank you!

Do you happen to know which device special file is associated with this UART? I am going to guess that in the bootloader stage it is “/dev/ttyS0”, which is for the serial console. If the bootloader detects serial UART activity on that particular UART during boot, then it will assume that there is activity requesting dropping into the U-Boot prompt/console.

If you happen to have another UART of the correct level setting, and assuming it is set to 115200 8N1 (no CTS/RTS flow control), then you might see activity by connecting to this (instead of loopback mode). If so, then that is the problem, and you’d have to either use a different UART, or else disable serial console on that UART during bootloader stage.

Hello!
How do I disable the serial console on this UART during the bootload phase? Now that I’ve opened the i2c@c250000 let /dev/ttyTHS2 get to work. Thank you!

That information is somewhere in the bootloader docs, but I don’t know from memory. Would someone have a reference URL to describe disabling or changing the serial console port in boot stages?

Incidentally, I still don’t know why “/dev/ttyTHS2” is group “tty”. This is somewhat unusual since this is the DMA-capable driver, but earlier boot stages always use the legacy driver.

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