Minicom/serial/ttyS0 issue on Raspberry Pi

[gwu22]

Hi,

I am using RPI GPIO TX, RX, and GND pins to connect to a serial port on a network device. It was working months ago with minicom but now I am having a strange problem. I tried using minicom, screen, cu but all are having the same problem. Its almost like the RPI console is 'leaking' into the serial port input. I get text such as 'Login incorrect' and 'Raspbian GNU/Linux 11 rpi3bplus ttyS0' being sent without my input to the network device. The network device keeps returning 'Unknown command' and then starts having an offset scrolling issue.

I am using the following minicom command: minicom -b 9600 -o -D /dev/ttyS0

I've attached a screenshot showing an example.

What may be causing this? How do I fix it?

Thanks.

[cleverca22]

is there a console=serial0 in /boot/cmdline.txt?

[gwu22]

is there a console=serial0 in /boot/cmdline.txt?

There was! I removed it and everything is working again!

Thanks so much!