I am currently attempting to control the Arduino Uno's Tx and Rx LEDs.
These are connected to digital pins 0 and 1 respectively, which are AFAIK, PD4 and PD5.
They are held at +5V, so I assumed that they would switch on when PD4,5 were driven low, however this has not proven to be the case.
I would be immensely grateful if anybody could offer a solution.
The schematic I referred to is here: http://arduino.cc/en/uploads/Main/Arduino_Uno_Rev3-schematic.pdf