Tiny-BCU

Idea

• BCU without ready-to-use KNX Transceiver like OnSemi, Siemens or Elmos
• Small µC that reads/writes the bits to KNX bus and
• "emulates" a reduced KNX TPUART BCU protocol

Benefits

• No dependency to onsemi & co: OnSemi had several times delivery difficulties; Elmos can not be ordered when you're private person, Siemens is not cheap
• better handling wrt. bus powered supply
• easier to build, due to no QFN package
• Parts typically all available at german distributeros/electronic shops
• possibly different and thus easier communication protocol (I2C?)
• possibly more cpu cycles for the sketch due to caching on TinyBCU controller?!

Cons

• not that tiny as MicroBCU due to more parts on PCB
• possibly not significant cheaper than traditional BCU

Requirements

• Transceiver-Part: something to read/write the bits physically from/to KNX bus
• Controller-Part: something that can interpret the bits from transceiver and make it BCU-style readable + write the bits of a telegram to the transceiver
• Supply-Part: voltage and current from bus: at least 3.3V and 5V with about >=50mA, without creating interferrences on the BUS

Transceiver-Part

See: https://github.com/selfbus/hardware-incubation/tree/master/module/UPModule

Supply-Part

See: https://github.com/selfbus/hardware-incubation/tree/master/module/UPModule For instance one can also use the "Polulu" step-down modules to create 3.3V and 5V from up to 40V input. The are multiple candidates available, f.i. from TI

Controller-Part

Something like the Attiny85.

Features:

• Interrupt-Pin: https://hoeser-medien.de/2015/04/attiny85-interrupt-basierend-auf-pinchange-interrupt-library/
• UART via softserial
• ultra low power
• small and also in DIP available --> easy to solder. Even with socket one can remove the chip to program it.

Open questions: How to debug? Maybe develop with Arduino UNO and then port to attiny?

SW: See: https://github.com/selfbus/software-arm-lib/tree/master/sblib/inc/sblib/eib