Raspberry Pi Zero W / Raspbian 12 - UART serial port loopback test

Raspberry Pi Zero W / Raspbian 12 - UART serial port loopback test

1. Install minicom:
  sudo apt-get update
  sudo apt-get install minicom

2. Run raspi-config:
  sudo raspi-config

  Go down to this and press Enter:
    3 Interface Options

  Then go down to this and press Enter:
    I5 Serial Port Enable/disable shell messages on the serial connection

  Answer the questions in the same manner:
    Would you like a login shell to be accessible over serial? No
    Would you like the serial port hardware to be enabled? Yes
  
  Do Ok several times, then Finish.
  
  If you get a reboot question, do so since it needs to enable UART.

3. Connect a jumper wire between 8/GPIO14/RX and 10/GPIO15/TX.

4. Run this to start minicom:
  minicom -D /dev/serial0
 
5. Type something on the keyboard, the text you write is sent from pin 10 to pin 8.
   Disconnect the wire, try to type again, note that no text is printed.
   Reconnect and note that the text is printed again.

Source: https://forums.raspberrypi.com/viewtopic.php?t=178079 (klricks)