Hello,
I have a problem and I would like to have an advice.
I have a I2C bus 3.3 V and I want to connect an arduino uno to it. Arduino must be powered with 7V so I can't feed the arduino with the bus so I would like to have an alternative. Should I power the arduino with a batterie? and how would I connect it to the bus then? only with the gnd sda and scl?
Thank you for the help!
Arduino must be powered with 7V so I can't feed the arduino with the bus
Sorry that doesn't make any sense.
The 7V you feed into the power in jack gets reduced to 5V by the regulator, you can not run an arduino directly from 7V.
The I2C bus is an open collector bus, that means it just pulls down so you should have no problem in connecting it to a 3V3 I2C bus.
The only snag is that you will have to disable the Arduino's internal pull up resistors either by hacking the existing library or using something like the "master I2C" library which has calls to enable or disable the internal pull up resistors.
You can get it here:-
Only possible problem is, the high level threshold in an I2C bus for the arduino is 0,7*Vcc. Running on 5V that'll be 3,5V (According to th datasheet).
Nevertheless it'll work most of the time, but i would use one of these:
Or create something like it.
I WAS WRONG!
Just looked at the datasheet some more, the correct high level is 0,6*Vcc!.
That'll be 3V, not 3,5V.