[clarry]

> Over I2C, you can interact with 127 devices with just 2 pins.

In practice, I don't see that many chips offering 7 bits of address configuration. You buy a chip, it has a hardwired address. Maybe a pin or two for selecting another address.

[photojosh]

There was the design I did quite a few years ago now. Grabbed a old design, changed the board shape, put a third I2C device on. Everything powered up beautifully first go... and it was only then we worked out two of the devices from different vendors had the same I2C address. <facepalm>

[danellis]

That's still seven bits of address, though. If you're lucky, the hardwired part will be different enough between chips that you can still have a significant number of them on a bus.

[rcxdude]

I've yet to get above 4 devices without conflicts. Even with evenly distributed addresses, you reach about 50% chance of conflict with 13 devices because of the birthday paradox.