I've just tried this, being back in the office, and booting without the UART cable attached and subsequently plugging it does get me a login prompt.
One thing I have noticed is that there is no pull up on the RXD line - it actually has a pull down - which isn't ideal. If you can SSH into the Pi 5 (or use a keyboard and display), attach and detach the Debug UART cable while running this command:What you will see is that the RX line goes low when the cable is disconnected, when it should really stay high. You can try adding the following to /etc/rc.local to see if it makes a difference:However, the system isn't designed for hot-plugging, and there is the possibility of glitches on the lines that might be interpreted as "break" signals etc. This can cause getty to try a different baud rate, at which point your console is going to be non-responsive. You can check the current baud rate (from another console) using "sudo stty -F /dev/ttyAMA10 -a".
One thing I have noticed is that there is no pull up on the RXD line - it actually has a pull down - which isn't ideal. If you can SSH into the Pi 5 (or use a keyboard and display), attach and detach the Debug UART cable while running this command:
Code:
$ pinctrl poll UART_TX_FS,UART_RX_FSCode:
pinctrl UART_RX_FS puStatistics: Posted by PhilE — Wed Feb 28, 2024 10:42 am