Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View

A simple question: Can SMBUS devices and I2C devices mix together
and attach to SMBUS? Or I have use all SMBUS devices or all I2C devices
to attach to SMBUS?


Quoted text here. Click to load it

SMBUS is an extension of I2C (or TWI, as it is also called,
to avoid patent disputes with Philips). It has some special
limitations and special reserved addresses.

If the addresses of the devices do not conflict and the
special properties of SMBUS are not needed, yes.

I'm using SMBUS, I2C and TWI devices together on
a common bus bit-banged by the master processor.


Tauno Voipio
tauno voipio (at) iki fi

SMBus added special broadcast messages within the I2C protocol.  But
everything is still addressed the same way, so unless a device is actually
listening for the broadcast messages, they are benign.  Like Tauno, I
implemented a system with a mix of SMBus and I2C devices without issue.

That said, one of the items SMBus allows is for the pullup voltage to extend
up to 12V, whereas every I2C-specific device I've encountered tops out at
5V.  If you are designing the whole system, there's no issues; if you are
interfacing with a black-box that has a 2-wire SMBus interface, I'd be sure
of a) whether that system expects your system to provide the pull-up or b)
that its' pullup is at a voltage that is not-harmful to yours.

Finally, Philips has the full I2C spec on their site, and you can find the
SMBus spec on www.smbus.org, and more info on the SBS (which spawned SMBus)
at www.sbs-forum.org.


Quoted text here. Click to load it

Site Timeline