I have an Arduino Uno and mbed sharing the same USB power supply/ground.

When connecting the two to allow I2C, I would have assumed I'd need to attach the Arduino's SDA pin (PC4) to the mbeds SDA pin, and the SCL pin to the corresponding SCL pin.

However, the examples I've seen seem to only make use of the Arduino's A4 and A5 pins.

Which is the correct (if any) way of doing this?

  • 1
    \$\begingroup\$ A4 and A5 on the Uno are the SDA and SCL pins. \$\endgroup\$
    – Samuel
    Feb 1, 2018 at 18:32

1 Answer 1


PC4 is A4 and PC5 is A5. No mystery here, you are just using different names.

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