Can i2c communication work with 2 devices of diff. VCC

mailtoarup · ‎2006-12-05

Posted on December 06, 2006 at 04:30

mailtoarup · ‎2006-11-27

Posted on November 28, 2006 at 01:27

Dear Sir,

I am having 2 devices On i2c bus .One is MCU with VCC = 5.0V and another

device with VCC = 3.3 V. Is it possible to have i2c communication between 2 devices in this case ?? Pls note both devices have i2c peripheral.

Pls help.

Thanks

Arup

wolfgang2399 · ‎2006-11-29

Posted on November 29, 2006 at 09:04

Hi Arup,

with a simple levelshifter your problem should be solved.

I attached a circuit diagram to this message. Hope it'll help you.

You should take the levelshifter to each of the both lines SDA and SCL.

When you take the mcu as master (clock only by the master 5V), you don't need the transistor and R1/C1 with the SCL-line.

C1 is not nessacary but brings a better pulse form.

R1 should be about 20 times the value of the pullup resistor of your 5V-busline (depends on the current gain of the transistor T1).

Regards

WoRo

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mailtoarup · ‎2006-12-05

Posted on December 06, 2006 at 04:30

Dear Mr. woro,

Thanks for the level shifter ckt.would you pls give a brief idea of how it works.

thanks,

Arup