[OT] My latest I2C bus – it’s time to brag

kender · Joined: 09 Aug 2004 Posts: 768 Location: Silicon Valley

Colleagues,

Thanks for the good tips on I2C bus that you have given me recently!

Now, I’d like to brag about the I2C bus in the project that I’ve just completed. It has the some interesting features:

* Four PICs: 1 master, 3 slaves. “simple” peripherals too: EEPROMs, I/O expander, pot.
* 2m cable. One of the slave PICs is at the end of the cable.
* The cable is hot-plugable.
* 300W @ 500kHz going through the same cable during I2C communication. High voltage in some modes of operation, high current in others. It’s EMI from the I2C’s perspective.
* Galvanic isolation of one of the branches.

Designing and bring it up was a lot of fun.

- Nick http://www.prolifictec.com

bsturm · Joined: 23 Feb 2009 Posts: 29

Congrats, it is a lot of work to get all that working reliably isn't it. I spent a solid week on my design with a master/slave board system. At first, it was not hot pluggable. By the end, it recovered nicely from cable unplugs and replugs.

newpicer_ · Guest

you both using the hardware i2c module?

bsturm · Joined: 23 Feb 2009 Posts: 29

I am using the hardware I2C...

kender · Joined: 09 Aug 2004 Posts: 768 Location: Silicon Valley

bsturm · Joined: 23 Feb 2009 Posts: 29

I haven't had a problem with the bus getting stuck recently, but I do have the WDT enabled just in case. It is not the nicest way of getting unstuck, but it is better than nothing.

I may end up writing my own master too, but I hope to not have to. I have an excellent book on I2C from Square1 Electronics with great examples if I need to get further into it.