I have a Raspberry Pi 4 with Buster and on top of it a 4G HAT.
This HAT allows communicating via RX and TX pins.
I want to communicate with this HAT via RX and TX pins but with an Arduino Nano. It works when Arduino and the 4G HAT are connected without the Raspi4.
The problem is that when I connect everything (Raspi4, 4G HAT on top of it and Arduino), the communication between Arduino and the 4G HAT is lost because both (from Raspi and Arduino) serial ports "collide".
How do I permanently deactivate RX and TX serial communication from Raspberry? I tried to disable Serial with
raspi-config but it does not work (e.g. GPIO15 is still high)