![]() These are different interrupt sources, not discussed here. The Arduino functions attachInterrupt() and detachInterrupt() can only be used for external interrupt pins. This interrupt will be automatically cleared when entering the ISR or by manually clearing the bit in the interrupt flag register. When an interrupt occurs, a flag in the interrupt flag register (TIFRx) is been set. It has 54 digital input/output pins (of which 15 can be used as PWM outputs). Interrupt masks are enabled / disabled by setting / clearing bits in the Interrupt mask register (TIMSKx). The Arduino Mega 2560 is a microcontroller board based on the ATmega2560. By default in the Arduino firmware interrupts are enabled. Interrupts can generally (globally) enabled / disabled with the function interrupts() / noInterrupts(). The according Interrupt mask must be enabled Instruction means a single machine instruction, not a line of C or C++ code.īefore a pending interrupt will be able to call a ISR the following conditions must be true: After the ISR has been finished, the running program is continued with the next instruction. An interrupt is an external event that interrupts the running program and runs a special interrupt service routine (ISR). The program running on a controller is normally running sequentially instruction by instruction. Each toggle, in software, requires AT LEAST 50+ cycles. Even if play accepted larger values for frequency, you couldn't achieve better than around 80KHz with the Tone library because the pin toggling is done in software. ![]() ![]() timer 1, or timers 3,4,5 on '1280), you could generate “tones” down to 1/8 Hz (one cycle every 8 seconds), although the library only accepts integers for frequency.Īfter all is said and done, because play() only accepts unsigned integers for frequency, the maximum frequency that can be produced is 65535 Hz - which, after rounding, results in a 65573.77 Hz “tone” on a 16 MHz part. You can’t use PWM on Pin 3,11 when you use the tone() function an Arduino and Pin 9,10 on Arduino Mega. To change the tone, you need to change the frequency. Arduino Mega Pinout Voltage Regulator-The voltage regulator converts the input voltage to 5V. It has a crystal oscillator-16 MHz, a power jack, an ICSP header, a USB-B port, and a RESET button. If you have a speaker connected to an output pin running analogOut(), you'll get a changing loudness, but a constant tone. Arduino Mega 2560 has 54 digital input/output pins, where 16 pins are analog inputs, 14 are PWM pins, and 6 are hardware serial ports (UARTs). When you use analogOut() to create pulsewidth modulation (PWM) on an output pin, you can change the on-off ratio of the output (also known as the duty cycle) but not the frequency.
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