Raspberry Pi Hat for KNX/EIB, the standardized protocol for smart home automation.
It allows your Raspberry Pi to connect to your home and operate it with your favourite KNX ready home automation software (Home Assistant, Jeedom, OpenHAB...) and makes an incredibly low cost Supervisor.
It can also act as a very cost effective KNX IP Gateway or Router with knxd and can be used to program your participants with ETS.

Features:

• Isolated KNX/EIB TP-UART interface (NCN5121)
• 12-24V up to 2A DC-DC step-down power suppy input
• Real Time Clock (DS3231)
• 32kb EEPROM (AT24C32)
• GPIO Compatible with Raspberry Pi and nanoPi M4 (jumpers for selecting correct UART pins: 8/10 or 19/21)

Installation:

KNX Hat provides 2 external connectors:
- DC 12-24V up to 2A Input for powering the raspberry Pi
- KNX/EIB Twisted Pair Bus connector

The Raspberry Pi MUST NOT be powered by 2 external sources at the same time, for example, USB and external DC 12-24V input.

Before installation: Select the correct UART pins by positioning both jumpers either on left or on right depending on your device GPIO pinout (see Compatibility section).

By default, Jumpers are positioned at left for Raspberry Pi compatible GPIO where UART uses Pin 8/10.

The DC-DC step-down converter is not soldered and is changeable for easier maintenance.

For mechanical mounting, it is recommended to use Raspberry Pi adapted 11mm M2.5 nylon spacers/standoffs (not provided, but can easily be found at all Raspberry Pi sellers). Metal spacers are not recommended as they may damage the PCB, and create short circuits. GPIO header and connections are close to mounting holes.

Usage:

For Raspberry Pi users: enable i2c, i2c-rtc and disable rpi3 bluetooth (shared serial line):

echo "i2c-dev" | sudo tee -a /etc/modules
echo "i2c-bcm2708" | sudo tee -a /etc/modules
echo "enable_uart=1" | sudo tee -a /boot/config.txt
echo "dtparam=i2c_arm=on" | sudo tee -a /boot/config.txt
echo "dtoverlay=i2c-rtc" | sudo tee -a /boot/config.txt
echo "dtoverlay=pi3-disable-bt" | sudo tee -a /boot/config.txt

Remove console=serial0,115200 console=tty1 in /boot/cmdline.txt

- KNX:

For maximum compatibility, the NCN5121 serial line is set to 19200bps and 8E1.
More details on knxd setup can be found on knxd project page.

For Raspberry Pi users: enable hardware serial:

sudo sed -ibak "s/console=serial0,115200//g" /boot/cmdline.txt
sudo systemctl disable hciuart # Disable Software uart
sudo systemctl stop serial-getty@ttyAMA0.service
sudo systemctl disable serial-getty@ttyAMA0.service

Install knxd:

sudo apt install knxd

Testing example:

knxd --eibaddr=1.1.63 --client-addrs=1.1.64:5 -D -T -S -b tpuarts:/dev/ttyAMA0
(/dev/ttyAMA0 may change depending of your device)
For knxd service to load at startup:
- Edit /etc/knxd.conf file
- Change KNXD_OPTS line
- Run sudo systemctl start knxd

- RTC:

echo "ds3231 0x68" | sudo tee /sys/class/i2c-adapter/i2c-1/new_device
(i2c-1 may change depending of your device)
You can then use commands like:
- sudo hwclock -s (set the system time from the RTC)
- sudo hwclock -w (set the RTC from the system time)
The RTC uses a usual CR2032 backup battery (not provided).

- EEPROM

echo "24c32 0x50" | sudo tee /sys/class/i2c-adapter/i2c-1/new_device
(i2c-1 may change depending of your device)

- RTC and EEPROM configuration persistence after reboot

Add these commands to rc.local:
echo "24c32 0x50" | sudo tee /sys/class/i2c-adapter/i2c-1/new_device
echo "ds3231 0x68" | sudo tee /sys/class/i2c-adapter/i2c-1/new_device
hwclock -s
(i2c-1 may change depending of your device)

Compatibility:

Jumpers on Left: (TX Pin 8 / RX Pin 10)

• Raspberry Pi
• Odroid C2/C4
• ROCK Pi 4
• ASUS TinkerBoard S
• Libre Le Potato
• BananaPi M4/M5

Jumpers on right: (TX Pin 19 / RX Pin 21)

• NanoPi M4