So I want to connect multiple LED Panels with dynamic addressing to a Master Controller. Seems like SMBus should be able to do that, however I don't find any Library for the Arduino framework. Does SMBus require Hardware implementation and if if works in Software is there a library for that and does it even work on the ATTiny?

  • SMBus and I2C are almost the same. Just a few specs between them. So... why SMBus and not I2C which is by far more ubiquitous?
    – Majenko
    Jul 26, 2021 at 14:12
  • @Majenko Because I really want the ARP feature of SMBus that enables me to use dynamic adressing. If there's a simpler solution to have dynamic adressing I'd love to hear that too Jul 26, 2021 at 14:49
  • The ATMega TWI Arbitration module only (afaict) works in master mode. So you would have to write a bit-banged slave emulation with arbitration built in. Doable, but not nice.
    – Majenko
    Jul 26, 2021 at 15:15
  • @Majenko so is there a better solution? Jul 26, 2021 at 15:24
  • ARP's your big sticking point. However since you need to allocate a UUID to each device anyway you could just allocate a unique I2C address to each device instead? Then you can scan the I2C bus looking for what I2C addresses exist.
    – Majenko
    Jul 26, 2021 at 15:30

1 Answer 1


The AVR chips lack hardware support for bus arbitration when operating as a slave device in I2C, which would be required for it to work as SMBus with ARP.

You would have to write your own bit-banged driver to act as a slave whilst monitoring the SDA pin whenever it transmits to look for bus collisions.

A better solution would be to allocate each device a unique address using an address space of your choosing (to give you enough addresses for uniqueness) at build / programming time. A bus of some design (maybe RS485 would be a good choice for this) can then be scanned looking for, and cataloguing, what addresses are in use.

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