How does the Keyboard.print() function work?

mmp153 · December 12, 2019, 9:33am

I am currently working with the keyboard library and was wondering how at the lower level these keyboard functions(APIs) work. I did find the definition for write(), press() and others but cannot find the println() definition here.
I'm a beginner to USB and cpp so please help me out here

pert · December 12, 2019, 10:13am

It inherits from the Print class, which is part of the Arduino core library. Each hardware package has its own copy of the core library, but the Print class should be the same on all of them. Here is the implementation in Arduino AVR Boards:

github.com

arduino/ArduinoCore-avr/blob/master/cores/arduino/Print.cpp

/*
 Print.cpp - Base class that provides print() and println()
 Copyright (c) 2008 David A. Mellis.  All right reserved.
 
 This library is free software; you can redistribute it and/or
 modify it under the terms of the GNU Lesser General Public
 License as published by the Free Software Foundation; either
 version 2.1 of the License, or (at your option) any later version.
 
 This library is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 Lesser General Public License for more details.
 
 You should have received a copy of the GNU Lesser General Public
 License along with this library; if not, write to the Free Software
 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 
 Modified 23 November 2006 by David A. Mellis
 Modified 03 August 2015 by Chuck Todd

This file has been truncated. show original

In order to avoid this code duplication, Arduino has embarked on the ArduinoCore-API project, which allow all the hardware packages to share the non-architecture specific parts of the core library:

It's already in use in the Arduino megaAVR Boards and Arduino Mbed Boards cores, as well as a few 3rd party cores, but has not yet been used in the other official Arduino cores.

mmp153 · December 13, 2019, 4:36am

Thanks, had a look at keyboard.h where Print class is inherited and write() method is overridden.
Once again thank you @pert

pert · December 13, 2019, 4:37am

You're welcome. I'm glad if I was able to be of assistance. Enjoy!
Per

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How does the Keyboard.print() function work?

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