I2C Multi-Master Network?

Forum 2005-2010 (read only) Hardware Interfacing
1

I've been tinkering with an Arduino for a while now, and have happily got it talking to a variety of devices, and now an I2C RTC.

I have two Arduinos running different 'halves' of my application. Let's call them A (the slave) and B (the master). There's also an I2C RTC.

I'm wondering if there's any way I can have the slave (A) occasionally be a master so that it can get the time from the RTC. The rest of the time, it'd be a slave, waiting for the real master (B) to tell it what to do.

Of course, it's possible I could have the master (B) get the time and then push that into the slave (A), but that seems rather round-about to me. I can imagine that if both masters start talking at the same time Bad Things could happen, but I can't find anywhere to confirm.

Any ideas? Thanks for your help!

2

Hi,
you are right things will happen if you have two masters on the bus at the same time.
You get an error code from Wire.endTransmission for a failed transmission (you have to check the library sources for the error type), but the much easier solution is to have the a single master controlling the bus.

Don't be cruel to yourself :slight_smile:
Eberhard

3

Thanks for the confirmation.

So it looks like it's technically possible, although with quite a bit of exception handling, and possibly a light protocol layer to back off and wait after an error etc. In other words, it's quite nasty.

Thanks again - I think I'll keep it simple :wink: