I2C slave address - Choosing address for a slave

mvaraujo · Joined: 20 Feb 2004 Posts: 59 Location: Brazil

Hi!

How do you guys choose addresses for your I2C slave devices?

I have a situation that I'm communicating some different circuit boards using I2C (they are different PWBs but, they are inside the same product). There's only one master and the others are slaves. I can have a situation where memory IC or RTC will be populated on the master device board, but there's no other situation that I'll need to hang I2C application boards or ICs on the bus.

The answer could be: just choose any one! But I would like to read how you handle these issues!

Thanks,

Marcus Araujo
Brazil

rnielsen · Joined: 23 Sep 2003 Posts: 852 Location: Utah

Download the I2C specification at http://www.semiconductors.philips.com/acrobat/literature/9398/39340011.pdf. It will tell you what addresses are reserved and what range is valid to use. Just remember that the address needs to be an even number because the LSB is used as the R/W bit.

Ronald

mvaraujo · Joined: 20 Feb 2004 Posts: 59 Location: Brazil

Ronald,

That's exactly what I did before! Considering that few ranges that are reserved (0000xx, 1111xxxx, etc) you would take any number, right?

I understand the issue involving the R/W LSB bit, thanks!

Marcus

rnielsen · Joined: 23 Sep 2003 Posts: 852 Location: Utah

Looking at the address table, you could assign an address between 0x08 - 0xF6. If you have any other I2C devices in your design you might want to assign an address close to it's address but anything should work.

Ronald