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Topic: Trouble understanding physical pin numbers vs pin names (Read 494 times) previous topic - next topic


Jun 10, 2014, 02:03 am Last Edit: Jun 10, 2014, 02:22 am by makethings Reason: 1

I'm very new and I can't find a good explanation for understanding the relationship between physical pin numbers and actual pin names.

For example, I'm looking at a Leonardo schematic, physical pin 32 shows its pin modes as "(ICP3/CLK0/OC4A)PC7" with a given pin name of "IO13*". I can't for the life of me figure out why calling that pin "IO13*" makes any sense and where that correlation is made. It confuses me to see something like pinMode(13,OUTPUT); that's referring to IO13* not the actual 13th pin.

Furthermore, lets say I want to use physical pin 9, named "SCLK" in the Leonardo schematic, as a digital output. I'm not sure how to relate pin 9 to being a digital IO so I can pass it into the function pinMode();

Thank you for any help!

Here's a link to the Leonardo schematic for reference.


Look at pins_arduino.h for the mapping from port to software name.
There are 3 arrays that really define stuff - the first list the order of the ports, the 2nd lists the bits within that port.
Then there is the datasheet that maps the port/bit to a physical pin.

There are also several good guides/pictures that show the mapping, as well as the chart linked to on the Products/Leonardo page
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.


Thank you! This is exactly what I was looking for.

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