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)
The 4G HAT presumably uses the serial port for a reason.
Serial is point to point protocol, so only 2 devices can be used.
If you want to use Arduino don’t use the Pi or vice versa.
Your question is somewhat unclear, but the Pi4 has 4 additional UART which can be used. See https://raspberrypi.stackexchange.com/a/107780/8697
It is simple to disable the Pi serial – Pins 14/15 will then be configured as inputs, so should have no impact.
NOTE most Arduino have 5V I/O so need level converters to connect to the Pi.