Thread: IF statement not working within a WHILE loop

  1. #1
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    Oct 2020
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    Question IF statement not working within a WHILE loop

    I have this piece of code which is triggered when a bit is set high (the bit is set high when an interrupt occurs). It works when I have a delay in place, but not without. Can anyone explain why?
    Code:
    while (1) {
    //  _delay_us(1);
        if (myFlags & (1 << serialAvailable)) {
          sendChar('Q');
          myFlags &= ~(1 << serialAvailable);
        }
    }
    If it matter, this is for an AVR microcontroller.
    So if I remove those comment symbols, it works. I cannot understand why?
    The only way I can get this to work is if I change...
    Code:
    if (myFlags & (1 << serialAvailable)) {
    to...
    Code:
    if (1) {
    Could this just be a artefact of the Atmel micro, or is this something with the code itself?

    john.c -> I cant reply, but yes I do. That is fixed but still the issue persists
    Thanks.
    Last edited by AirborneFluff; 10-31-2020 at 12:31 PM.

  2. #2
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    Dec 2017
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    1,042
    I assume you mean to use bitwise AND (&), not logical AND (&&).
    Philosophy is a battle against the bewitchment of our intelligence by means of language. - Wittgenstein

  3. #3
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    Arizona, USA
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    How is myFlags declared? Is it shared with an ISR? If it is, then it should be declared with volatile.

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