After a lot of reading: does the UNO Rev 3 board have on-board pullup resistors for the I2C lines A4 and A5; 10K from what I read? I can't find them on the schematic. Also can these pullups be disabled - i.e. programmatically or manually disconnect the resistors from the two lines?

UNO board I2C pullups? Can be enabled/disabled?

system February 24, 2013, 10:59pm 6

That seems all good, except the breadboard.
So many people have bad connections with breadboards.

What I2C chip are you using ?
What is your code ?

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