Interrupts
Interrupt Code Sample
Sample Code to to toggle an LED when a button triggers an interrupt.
//Define LED and switch connections const byte ledPin = 13; const byte buttonPin = 2; // Boolean to represent toggle state volatile bool toggleState = false; void checkSwitch@) { //Check status of switch // Toggle LED if button pressed if (digitalRead(buttonPin) == LOW) { // Switch was pressed // Change state of toggle toggleState = !toggleState; // Indicate state on LED digitalWrite(ledPin, toggleState); } } void setup() { //Set LED pin as output pinMode(ledPin, OUTPUT) ; // Set switch pin as INPUT with pullup pinMode (buttonPin, INPUT_PULLUP) ; //Setup Serial Monitor Serial. begin (9600); // Attach Interrupt to Interrupt Service Routine attachInterrupt(digitalPinToInterrupt(buttonPin),checkSwitch, FALLING); } void loop() { // 5-second time delay Serial.println("Delay Started"); delay (5000); Serial.println("Delay Finished"); Serial.println("....... }
Pin Change Interrupts
Arduino microcontrollers have a limited number of pins that are hardware interrupt compatible.
To get around this limitation, we can use a pin change interrupts on almost all pins.
Enable Port B
Each port has a mask to enable particular pins.
Activate Pin D12 on Port B
Interrupt Service Routines are pre-defined for each port
Define the ISR
We must rest the interrupt by writing a "1" to the corresponding bit of the PCIFR register. This is not required when using an ISR.
Note about Pin Change Interrupts
Analyzing the Following Code
static uint8_t saveTCCR1A, saveTCCR1B; static inline void capture_init(void) { saveTCCR1A = TCCR1A; saveTCCR1B = TCCR1B; //reset TimerCounter 1 TCCR1B = 0; TCCR1A = 0; TCNT1 = 0; TIFR1 = (1<<ICF1) | (1<<TOV1); TIMSK1 = (1<<ICIE1) | (1<<TOIE1); } static inline void capture_start(void) { TCCR1B = (1<<ICNC1) | (1<<ICES1) | (1<<CS10); } static inline uint16_t capture_read(void) { return ICR1; } static inline uint8_t capture_overflow(void) { return TIFR1 & (1<<TOV1); } static inline void capture_overflow_reset(void) { TIFR1 = (1<<TOV1); } static inline void capture_shutdown(void) { TCCR1B = 0; TIMSK1 = 0; TCCR1A = saveTCCR1A; TCCR1B = saveTCCR1B; } #define TIMER_OVERFLOW_VECTOR TIMER1_OVF_vect #define TIMER_CAPTURE_VECTOR TIMER1_CAPT_vect
References
Reference | URL |
---|---|
Understanding Arduino Interrupts | Hardware, Pin Change & Timer Interrupts | https://www.youtube.com/watch?v=wIcC8-g9Lnw |
Electronic Basics #30: Microcontroller (Arduino) Timers | https://www.youtube.com/watch?v=IdL0_ZJ7V2s |
Configuring & Handling ESP32 GPIO Interrupts In Arduino IDE |