Arduino Leonardo "secret" pins

I know, I posted a similar topic a few hours ago but this is a little bit different, sorry.
I found out today that the Leonardo has 4 hidden pins - D14, 15, 16, and 17.
It's even on the atmega32u4 processor on eaglecad.
the screenshot is on the attached file.
However, the leonardo has only to pin 13, and the 4 pins are left out.
I'm designing a board that includes these 4 pins.
If I type in digitalWrite(17, HIGH), will I be able to turn the pin on?
Sorry, I don't have a Leonardo, so I would like someone to test it out for me.


Look in your installation tree.

Pin definitions are in:

_BV definitions are in"

(at least for a linux installation)

As shown in the attached image, pin 17 is connected to RX LED. So you can break it out and use it but that pin is blinked when data is received over Serial (including uploads over USB) so it's not very useful for applications where you have incoming serial communication and you need complete control of the pin. I've used it as an indicator on the Pro Micro, which doesn't have an LED on pin 13, but it's not very useful for that purpose if there is constant Serial data being received. The other "hidden" pins are actually connected to the ICSP header on the Leonardo. From hardware/arduino/avr/variants/leonardo/pins_arduino.h:

// Map SPI port to 'new' pins D14..D17
#define PIN_SPI_SS    (17)
#define PIN_SPI_MOSI  (16)
#define PIN_SPI_MISO  (14)
#define PIN_SPI_SCK   (15)