DB2.1 1.0

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DB2.1 v1.0 - 2 Button Doorbell
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Developer Alexander Christian
Status In Development
Microcontroller/Board M0dularis+
KNX connectivity MicroBCU


PCB replacement for 2n Entrycom IP Uni doorbell. It will have 2 buttons with RGB background LED light and a speaker for PCM WAVE playback.


M0dularis+ is used as base-controller.

Description Pin Description
GND / KNX GND 1 2 GND from 24V Input
SJ: 3.3V VCC 3 4 24V from 24V Input
PA22/SDA SDA / IO0 5 6 IO3 SJ: PA02/A0 PCM Audio Output via DAC on A0
PA23/SCL SCL / IO1 7 8 ExtINT Application / IO2 SJ: PA18/D10*# ReedRelay Speaker Enable
PWM R on LED1 PA09/D3*# Option0 9 10 Option7 PA17/D13*# PWM R on LED2
PWM G on LED1 PA08/D4* Option1 11 12 Option6 PA16/D11*# PWM G on LED2
PWM B on LED1 PA15/D5*# Option2 13 14 Option5 PA20/D6*# PWM B on LED2
Button 1 PA14/D2# Option3 15 16 Option4 PA21/D7# Button 2

Solder-Jumper (SJ) configuration:

  • IO3: SJ to A0
  • IO2: SJ to D10
  • Application connector: SJ to 3.3V
  • Frontend connector: SJ to 3.3V (but is unused)
  • I2C (on IO0/IO1): PullUp

* = PWM capable
# = INT capable

24V from yellow/white bus connector -> LM2596 step-down buck converter module -> 5V supply voltage for amplifier + LEDs


The software enabled the user to fully have control over the buttons. One idea ist to have multiple states for the buttons. For instance

  • Default (white background light): Rings the bell
  • Postman (yellow background light): Ringing the bell will playback a wave file, telling where he can put the package that you are waiting for. Additional things can be triggered by calling a KNX GroupAddress, f.i. open the garage door half a meter so safely store the package.
  • ...

Open Questions

  • how to get files onto the SPI flash?!

-> see filetransfer via Bus PoC

User Documentation

Developer Documentation

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