Delay in ISR function

Using Arduino Programming Questions
1

I have an interrupt function that is triggered by a button being pressed
And I want that function to show some data on the lcd display for a specific amount of time (4 seconds for example )
I know I can't use delay and millis, so my question is how to delay a specific amount of seconds with a for loop that runs without instructions?
Example : for(int I=0;I<=some number;I++){nothing} ---> delay 4 seconds

1 Like
2

You don't. In fact, there's no reason to use an interrupt for a button press.

But, if you insist on doing so (for "learning exercise", etc), then just set a flag in the ISR noting that the button has been pressed. Then pick up (and clear) that flag in your non-ISR main code. Do whatever task time-consuming task is required there.

1 Like
3

See the blink without delay example in the IDE, without delay.

4

Your for loop will be optimized away to nothing when the compiler sees that it does nothing.

5

But you can use delayMicroseconds(). It can only delay up to 65535 microseconds so you have to call it multiple times. Let's do 50 milliseconds (50,000 microseconds, 1/20th of a second) each time to make the calculation easier.

If you want your sketch to freeze for 4 seconds:

  // 4 seconds / 0.050 seconds = 80
  for (int i=0; i < 80; i++)
    delayMicroseconds(50000u); // 50 ms

It will be interesting to see what goes horribly wrong when you keep interrupts disabled that long. :slight_smile:

6

You should not use delay(), millis(), any sort of I/O that relies on other interrupts, or spend any more time in an interrupt than is necessary. If you are just processing a button press and your code is written properly then you should not need interrupts at all. I have written several rather complex controllers using an Arduino and did not use any interrupts other than those required for the serial interface and libraries I used.

Interrupts should not be used unless you thoroughly understand the hardware and timing requirements of the device as a whole.

7

Hello inkdomink
Do you have a sketch? If YES, post the current sketch to see how we can help.
Post it well formated, with comments and in so called code tags "</>" and schematic.
Have a nice day and enjoy coding in C++.

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