Using KNX Ultimate with kBerry on Raspberry Pi 3 (UART / FT1.2)

This guide explains how to connect a kBerry KNX interface directly to a Raspberry Pi 3 and use it with KNX Ultimate over the hardware UART (ttyAMA0) using the FT1.2 (TPUART) protocol.

This procedure was tested with Raspberry Pi OS Bookworm on a
Raspberry Pi 3 (November 25, 2025).

1. Prerequisites

• Raspberry Pi 3 (Model B or B+)
• Raspberry Pi OS (Bookworm recommended)
• kBerry KNX interface mounted on the GPIO header
• Node-RED with KNX Ultimate installed
• Basic terminal access (SSH or local console)

2. Wiring / Hardware Overview

The kBerry uses the Raspberry Pi’s primary UART:

• TX / RX: GPIO14 (TXD) and GPIO15 (RXD)
• GND: Common ground between Raspberry Pi and kBerry
• Power: Provided via the GPIO header

Make sure the kBerry is properly seated on the Raspberry Pi GPIO header and that no other HAT is conflicting with those pins.

3. Disable Bluetooth and Enable the Hardware UART

3.1 Edit the correct config file (Bookworm)

sudo nano /boot/firmware/config.txt

Add (or ensure you have):

enable_uart=1
dtoverlay=pi3-disable-bt

3.2 Disable ModemManager (if present)

sudo systemctl disable --now ModemManager

3.3 Disable Bluetooth service

sudo systemctl disable --now bluetooth.service

4. Disable Serial Login Console / Enable Hardware UART

Start the configuration tool:

sudo raspi-config

Then navigate through the menus:

• Interface Options (or Interfacing Options on older systems)
• Serial Port

You will see two questions:

• “Login shell to be accessible over serial?” → choose No
• “Enable serial port hardware?” → choose Yes

Finish and exit raspi-config, then reboot when asked (or manually later).

5. Verify UART

ls -l /dev/serial0
ls -l /dev/ttyAMA0
dmesg | grep tty

Expected:

/dev/serial0 -> ttyAMA0
/dev/ttyAMA0 exists

6. Add Node-RED user to dialout

Linux uses the dialout group to grant access to serial ports like /dev/ttyAMA0 or /dev/ttyUSB0.
The user that runs Node-RED must belong to this group, otherwise KNX Ultimate cannot open the serial port.

If you installed Node-RED with the official script, the service user is usually nodered. On some systems it may be pi or another user; adapt the commands accordingly.

Check the current groups:

id nodered   # or: id pi

Add the user to the dialout group:

sudo usermod -aG dialout nodered

After changing group membership, log out and log in again for that user, or simply reboot:

sudo reboot

This step is only needed when you use a serial gateway; pure KNX/IP setups do not require dialout.

7. Configure KNX Ultimate

In the KNX Ultimate gateway node:

• Interface type: Serial FT1.2 / TPUART
• Serial port: /dev/ttyAMA0
• Baud rate: 19200
• Data bits: 8
• Parity: Even
• Stop bits: 1

8. Troubleshooting

No /dev/ttyAMA0

• Check /boot/firmware/config.txt entries
• Reboot
• Re-check dmesg

/dev/serial0 → ttyS0

• dtoverlay=pi3-disable-bt not applied
• Re-check config file path
• Reboot

Serial cannot be opened

• Ensure the Node-RED user is in dialout (id nodered)
• Check that no other program is using /dev/ttyAMA0
• Verify that the KNX Ultimate gateway node is configured for /dev/ttyAMA0

Done.