Custom Dobiss master hardware
This solution to replace the master of this Dobiss lighting switch bus consists of:
- A Raspberry Pi 5 4GB
- A Raspberry Pi Pico
- A logic level shifter (Adafruit 4-channel I2C-safe Bi-directional Logic Level Converter - BSS138)
- A 1k Ohm resistor
- A SH-C30A DSD TECH USB to CAN Bus Adapter
The Pi Pico handles the low level communication. It generates the reset pulse and requests the unique ID if a presence pulse is detected. The unique ID is received and communicated to the Pi 5 by UART.
The Pi 5 acts as power supply and processes the messages which are sent on the bus.
The low side of the logic level shifter is connected the 3.3 V pin (pin 1) and a ground pin (pin 9) of the Pi 5. One of its low side pins (A4) is connected to a GPIO pin (pin 20) of the Pi Pico.
The high side of the logic level shifter is connected to the 5V pin (pin 2) and a ground pin of the Pi 5. Finally a high side pin (B4) is connected to the data wire of the bus (D).
The bus itself (the D wire) is connected to the 5V pin with a 1K Ohm pullup resistor.
The Adafruit Permaboard shows the Raspberry Pi Pico, Logic Level Shifter and connections to other components.
A. This is the screw terminal for the 5V side of the board. It powers both the Raspberry Pi pico on pins 38 & 39, powers the high side of the logic level shifter and to the One Wire Buses using the pull up connectors. The screw terminal is connected to pins 4 & 6 of the Raspberry Pi 5.
B. These pins connect to pins 1 & 2 of the Pi Pico which is the UART interface. It connects to the pins 8 & 10 of the Raspberry Pi 5 and communicates the received circuit ids to the RPB 5.
C. This is the screw terminal for the 3.3V side of the board. It powers the low side of the logic level shifter. The screw terminal is connected to pins 1 & 9 of the Raspberry Pi 5.
D. These wires are connected to the data wire side of the UTP cable going to the lighting switches. (This wire is connected to the terminal 'D' in the original Dobiss Module. Do not connect the bus to both the Dobiss Module and the microcontroller!)
E. These wires are connected to the ground wire of the UTP cable going to the lighting switches. (This wire is connected to the terminal 'M' in the original Dobiss Module. Do not connect the bus to both the Dobiss Module and the microcontroller!)