![]() 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. Interrupt masks are enabled / disabled by setting / clearing bits in the Interrupt mask register (TIMSKx). 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). Program a timer to generate an interrupt every 1 microsecond. ![]() It determines the time between pulses using micros (). In Arduino, there is a handy function called micros() which return you the microseconds. The program running on a controller is normally running sequentially instruction by instruction. The external interrupt routine in my code is for a tachometer. 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. These SAMD Hardware Timers, using Interrupt, still work even if other functions are blocking. To change the tone, you need to change the frequency. GitHub - khoih-prog/SAMDTimerInterrupt: This library enables you to use Interrupt from Hardware Timers on an SAMD-based board. If you have a speaker connected to an output pin running analogOut(), you'll get a changing loudness, but a constant tone. 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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