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Boardwalk :: Forum List Luminary Micro Forums Design Stellaris 2006

kcrajesh

Junior Boarder 		Click here to see the profile of this user

2007/01/25 04:05

I2C and 5v slave

Is it possible to interface a 5volt slave device on the I2C bus of the 811 Eval. board directly or do should an approprite bidirectional level shifter be used ?

I understand that the 811 pins are 5 volts tolerant, however I am worried about the OLED.

According to the I2C spec the I2C lines are not driven high, except by the external pull up resistors, but I am not too sure.

TIA.

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magnuslundinse

Gold Boarder 		Click here to see the profile of this user

2007/01/25 12:15

Re:I2C and 5v slave

I would try to run the i2c lines at 3.3V. There is already a pullup to 3.3V on the 811 board.

The slave pins should be configured as Open Collector anyway and for most chips 3.3V is sufficient as a high input level. This should work if the clock is not to fast.

Regards,
Magnus

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ellehoej

Fresh Boarder 		Click here to see the profile of this user

2007/01/26 10:55

Re:I2C and 5v slave

Hi.

Here is a very simple and elegant solution:

http://www.standardics.nxp.com/support/documents/i2c/pdf/an97055.pdf

Regards
Frederik Ellehoej

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