hi everyone

I am referring to pin .I2C SCL (Port D.0) labelled RX .

I am using the i2c-test program to cycle between 3 states - making this pin as input, making this as output and driving it low, making this as output and driving it high.

The problem is when I drive it high it only goes to 2.5 V. On driving it low I get 0 V which is fine. On turning it to input I get 0.42 V even though it is pulled high.

On repeating the same procedure on I2C SDA (Port D.1) labelled TX, it works fine. When I turn this pin to input it gives me 5V, because it is pulled up. On driving it low I get 0 V. And on driving it high I get 5 V. I should be getting the same behaviour from the other pin as well.

I removed the pull-up to VCC from the SCL pin and even now if I drive it high I only get 2.5 V. On turning it to input or driving it low I get  0 V.

Any help would be greatly appreciated.

Vaibhav
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http://guidance.aero.iisc.ernet.in/vaibhav