The internal pullup (enabled in setup) forces the pin HIGH normally. To test this, just connect a wire (or switch) between D2 and Ground. This example shows how, even though the main loop is doing nothing, you can turn the LED on pin 13 on or off, if the switch on pin D2 is pressed.
ARDUINO MILLIS INSIDE INTERRUPT UPDATE
The second experiment was to compile and disassemble your ISR.PinMode (LED, OUTPUT) // so we can update the LEDĭigitalWrite (BUTTON, HIGH) // internal pull-up resistorĪttachInterrupt (digitalPinToInterrupt (BUTTON), switchPressed, CHANGE) // attach interrupt handler Which confirms the cycle count of the first part of this answer. 62.5% is exactly 10 out of every 16 CPU cycles, The reti instruction) costs 62.5% of the CPU power, leaving 37.5% to Shows that processing an empty interrupt (an ISR consisting solely of With the sei() statement, the frequency drops to 375 Hz. That's exactly what it does if the sei() statement is commented out. The program is meant to generate a 1 kHz signal on pin 2, and In the first experiment, I used your initializeTimer0CTC_Mode()įunction to interrupt every microsecond the following program: // This ISR consists of a sigle `reti' instruction.ĭDRD |= _BV(PD2) // PD2 = digital 2 as output There is no way you can do half of this in only 6 cycles.Įdit: I did a couple of experiments to gain more insight on the cost
pushing to the stack any register your ISR (return from interrupt) that takes 4 cycles. When the ISR is done, it executes the reti instruction The interrupt vector itself is a jmp instruction that takesĢ cycles. (save the program counter, load the interrupt vector and clear the I bit
The CPU needs 4 cycles to prepare itself for servicing the interrupt #include Įxtern void initializeTimer0CTC_Mode (void) But there is some issue and I'm not able to get it working correctly.
ARDUINO MILLIS INSIDE INTERRUPT CODE
I wrote this code to get micros() and millis(). Otherwise we could go for directly 1 msec interrupt (maybe using timer0). Inside ISR, we could update the microsecond counter and if it reaches 1,000, we could update the msec timer count. In such case, we have to use CTC mode with OCR0A=15. In one case, we can go for timer0 without prescaler and use 1 µsec interrupts. Any specific reason why this was implemented this way? Instead they make use of 1,024 µsec interrupts and manipulate. Arduino millis() does not make use of one millisecond interrupt.
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