I2C and HotPlug

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#1
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Hi all,

Here I come again back to the best AVR forum to ask for some experience.
I'm planning to do some I2C communications, single master, multiple slaves. The idea is to have a logging station, so each slave is nothing but a simple sensor (temperature or whatever).

This is the question: is it neccesary to power on every slave before starting the master?
It's obvious that the master won't be able to find them otherwise, but what I mean is..

1) Do the avr pins have high-impedance when the avr is off? That should be so in order for the pullups (at the master side for instance) to keep the lines high. (I should test this, I haven't yet)

2) if a device is powering on and other two are communicating, will it be able to turn on silently in order to avoid interference on the lines?

Maybe I should try these first in practice, but I wanted to know other's experience with this.

Thanks a lot!

Carlos

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When the avr is not powered up then you can phantom power by having volts on a pin, remeber the protection diodes.

Do you intend to have an AVR at every logging point? Then if so why the I2C, look at using the usarts in multidrop mode.

Keep it simple it will not bite as hard

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Well it's good news to hear that about pins.

Yes, I'm planning to have an AVR at every logging point, why do you think usart in multidrop mode will be better?

you mean like avr's multiprocessor mode?