clockCyclesPerMicrosecond()/ clockCyclesToMicroseconds()/ microsecondsToClockCycles()

Abstract

These macros convert the number of clocks and time(in microsecond).

Source Code

The clockCyclesPerMicrosecond()/clockCyclesToMicroseconds()/microsecondsToClockCycles() is defined in hardware/arduino/avr/cores/arduino/Arduino.h as below.

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#define clockCyclesPerMicrosecond() ( F_CPU / 1000000L )
#define clockCyclesToMicroseconds(a) ( (a) / clockCyclesPerMicrosecond() )
#define microsecondsToClockCycles(a) ( (a) * clockCyclesPerMicrosecond() )

The clockCyclesPerMicrosecond() shows the number of clocks a micro second.

F_CPU is (maybe) uses uno.build.f_cpu defined in hardware/arduino/boards.txt. In case of Arduino Uno it is 16000000(=16MHz). As a second is 1000*1000 microseconds, it is 16 which is F_CPU divided by 1000000.

The clockCyclesToMicroseconds() converts the number of clocks to microseconds.

The microsecondsToClockCycles() converts the microseconds to the number of clocks.

Version

Arduino AVR Boards 1.8.6

License

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/*
  Copyright (c) 2016 garretlab.
  Added source code explanation by garretlab.
*/

/*
  Arduino.h - Main include file for the Arduino SDK
  Copyright (c) 2005-2013 Arduino Team.  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
*/

Last Update

July 31, 2025