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--- en:iot-open:programming_fundamentals_rtu:interrupts_and_sub-programs [2018/02/02 14:20] – Agrisnik
+++ en:iot-open:programming_fundamentals_rtu:interrupts_and_sub-programs [2020/07/20 09:00] (current) – external edit 127.0.0.1
@@ Line 73: / Line 73: @@
 ===== Interrupts =====
-//Interrupt// is a signal that stops the normal execution of a program in the processor, to be able to handle tasks with higher priority. These tasks usually are called //Interrupt service routine (IRS)// or interrupt handler. Interrupt signals can be generated from external source, like change of value on the pin and from internal source, like timer. After interrupt signal is received processor stops code executing the code and starts the IRS. After completing IRS, the processor returns to normal code execution state.
+//Interrupt// is a signal that stops normal execution of a program in the processor, to be able to handle tasks with higher priority. These tasks usually are called //Interrupt service routine (IRS)// or interrupt handler. Interrupt signals can be generated from external source, like change of value on the pin and from internal source, like timer. When the interrupt signal is received, the processor stops executing the code and starts the IRS. After completing the IRS, the processor returns to the normal program execution state.
-IRS should be as short as possible and the return type of it is void. Some of normal Arduino functions does not work or behaves differently in the IRS, for example, //delay()// function does not work in the IRS. Variables, used in the IRS must be volatile variables.
+IRS should be as short as possible and the return type of it is void. Some of normal Arduino functions do not work or behave differently in the IRS, for example, //delay()// function does not work in the IRS. Variables, used in the IRS must be volatile variables.
 Interrupts are used to detect important real time events, that occur during the normal code execution of the code, without continuously checking them, like pushing a button.
-Different Arduino types has different external interrupt pin availability. In most Arduino boards pins 2 and 3 are usable for interrupts.
+Different Arduino types has different external interrupt pin availability. In most Arduino boards pins number 2 and 3 are used for interrupts.
+To attach interrupt, the function //attachInterrupt(digitalPinToInterrupt(pin), ISR, mode)// is called. This function has 3 parameters:
+  - //pin// – the number of a pin number where the interrupt signal generating device will be attached,
+  - //ISR// – the name of a function of interrupt service routine,
+  - //mode// - defines when interrupt signal is triggered. There are four basic //mode// values:
+      * LOW - interrupt is triggered when the pin value is LOW,
+      * HIGH - interrupt is triggered when the pin value is HIGH,
+      * CHANGE - interrupt is triggered when the pin value is changed,
+      * RISING - interrupt is triggered when the pin value is changed from LOW to HIGH.
+The example program that uses interrupt:
 <code c>
+volatile bool button =0; //a variable to save button state
 void setup() {
   pinMode(13,OUTPUT);       //define LED pin
@@ Line 87: / Line 100: @@
   attachInterrupt(digitalPinToInterrupt(2),ButtonIRS,FALLING); // attach interrupt to button pin
 }
-volatile bool button =0; //variable to save button state
 void ButtonIRS() {  // IRS function
@@ Line 98: / Line 109: @@
 }
 </code>
+**Check yourself**
+. What are the built-in functions used for?
+  * To reduce the size of the program
+  * To delete unnecessary functions
+  * To simplify the source file
+  * To increase the speed of the program
+. Which of the following statements are true?
+  * built-in functions must return a value.
+  *  built-in functions can not return values.
+  * The compiler can ignore the declaration of the built-in function.
+  *  built-in functions can not contain more than 10 lines of code.
+. Is it possible to guarantee that the declared built-in function is really built-in?
+  * guarantee is not possible, in each individual case it is different
+  * can be confidently ensured that the function you have declared as built-in is really built-in

en/iot-open/programming_fundamentals_rtu/interrupts_and_sub-programs.1517581247.txt.gz · Last modified: 2020/07/20 09:00 (external edit)