I was a little shocked when I found out that on my mega there are two unconnected interrupts. U see, in my project I need I2C and all 4 serials, that leaves me only with 2 free interrupts, but I need 4. When I looked into arduino code, I saw all interrupts mapped, so is only problem that they are not connected on reference board? Im going to create my own board, so if simply connecting them would solve my issue, it would be nice.

Thanks for clarification :slight_smile:

Check out the pin change interrupts.
They're a little slower than the dedicated external interrupts.

PCINT are nice, but im new to arduino/atmega programming and dont know how to properly use them. Im usualy more VHDL guy :slight_smile: Thanks for answer anyway :slight_smile:

Do you really need interrupts? Many people here think they do when in reality they don't. The Arduino can do lots of stuff very quickly enough not to need interrupts in most cases.

What are you planning to use the interrupts for?