RRU Setup Raspberry PI

Set up the Raspberry Pi 4:

Configure the internal serial port:

Add user to dialout group:

sudo usermod -aG dialout $USER
newgrp dialout # or log off / log in

Disable serial console:

sudo systemctl stop serial-getty@ttyS0.service
sudo systemctl disable serial-getty@ttyS0.service

Set overlay: This moves /dev/ttyAMA0 to where the UART RX/TX pins are located (GPIO14/15).

# Backup the config file
sudo cp /boot/firmware/config.txt /boot/firmware/config.txt.bak
sudo sh -c "echo 'dtoverlay=miniuart-bt' >> /boot/firmware/config.txt"

Enable UART:

sudo raspi-config
# Select "Interface Options" > "Serial Port" to enable UART
# Login Shell -> No
# Hardware -> Yes
# Reboot

Check if the serial port is present:

ls -hal /dev/ttyAMA0

This should return something like:

oe3anc@rru:~ $ ls -hal /dev/ttyAMA0    
crw-rw---- 1 root dialout 204, 64 Apr 25 10:12 /dev/ttyAMA0

Connecting the Raspberry Pi to the RRU

On the Pi 4, I used these pins:

Pi 4	RRU
14	TX
15	RX
17	NRST
27	PA
GND	GND

A good overview of the pinout: https://pinout.xyz/