* From sample interrupt code published by Noah Stahl on his blog, at:įunction: Init timer 2 to interrupt periodically. The loop function may be empty or not the LED should start flashing on download (well, literally, after Timer2init() is called). The sketch needs to #define LEDPIN, and setup() needs to call Timer2init(). The rest of that function is 1) the code to be run at each interrupt, and 2) the code code to reset the timer for the next interrupt.Īs written, this should drop in to a. The ISR() macro takes care of creating interrupt entry- and exit-code for an ISR instead a normal function's entry and exit, and of linking it with the proper interrupt vector. There is a table in the comments of some useful timing data from the data-sheet and my own calculations for reference to set up another timing scheme. Here's my slightly edited - mostly in the comments - version of Noah's code.Ĭall Timer2init() from the Arduino setup() function after you initialize any related data-structures or hardware, because timing - and interrupting - will begin once you do.į/ex, I used it to multiplex a 3-digit 7-segment display so I before initializing the timer, I initialized the display I/O registers and blanked the display data in the place where the ISR will look for it. When you disable interrupts with cli just before the delay call, you have the same problem. Inside the ISR those are turned off so delay just sits and waits forever for an interrupt thats not coming. Delay relies on a timer interrupt to measure the time. ![]() Look around his site for more useful Arduino interrupt examples. You can have a delay out in your code, just not in the interrupt service function itself. So, using these timers is not a good suggestion if you plan to use above options. His example cites the ATmega2560 I can confirm that it works with an ATmega328p as well. Arduino timers are reserved for buid-in functions: Timer0 is reserved fire a millisecond interrupt for the millisecond counter Timer1 is reserved for measuring time passed since the last reboot Timer2 is reserved for pwm timing. ![]() Timer2 is usually used for some PWM functions. With that and the data sheet, you should be able to adapt it to whichever interrupt you want to use - i.e., the interrupt whose normal function you can most afford to give up or are willing to modify. Noah Stahl's blog has an example of blinking a LED with Timer2.
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