Hi, all. This is my first post here, so please bear with me. I have some months of experience with Arduino, so not much. But I have a background in Electronics and do a lot of coding for work, so I've learnt relatively quickly. I am working on a low-power project. I'm planning to use an ATTiny85 w…

This should be volatile: [image] fepegar: boolean flag = false; This should probably be INPUT_PULLUP : [image] fepegar: pinMode(SWITCH, INPUT); You may have trouble using external interrupts to trigger the ATtiny85 when you progress on to using sleep modes. I'll try to find a referen…

[image] fepegar: This means that I have two options (I think): Three. Pin change interrupt.

[image] Coding_Badly: Three. Pin change interrupt. Hi, @Coding_Badly . Thanks for replying. I'm not sure what you mean. Pin change interrupt (PCINT) is my option 2.

[image] fepegar: Here's what the breadboard looks like. Although this is far from the worst I've seen, Fritzing diagrams are more or less useless. Please avoid posting them in the future. Instead, post a schematic, with pins appropriately numbered and/or labeled, and showing power supply conn…

[image] anon94801460: Although this is far from the worst I've seen, Fritzing diagrams are more or less useless. Please avoid posting them in the future. Instead, post a schematic, with pins appropriately numbered and/or labeled, and showing power supply connections. Thanks for the compliment…

I believe @JChristensen is the reference. Someone found that the documentation is not accurate and posted their findings on this forum. I recall it being @JChristensen . I found this .

Ah yes. There is a rich history to this and it catches a few people out from time to time. I'm quite alert to this problem, when I see other people potentially facing it, having spent many hours troubleshooting exactly that. I'd forgotten that @JChristensen discovered it before @nickgammon . At lea…

[image] 6v6gt: This should be volatile Thanks, @6v6gt . That fixed it. And more importantly, now I understand why it was failing. The commented line digitalWrite(LED_FLAG, flag); was the one that made flag not necessarily volatile. I wish compilers told us about these. [image] 6v6gt: This…

[image] fepegar: I wish compilers told us about these. The unfortunate thing is that the compiler cannot see this situation, hence the necessity to use the volatile keyword to tell it. The compiler usually attempts to use variables directly from registers if possible to avoid reloading these …

Mysterious behavior of ATTiny85 and hardware interrupts

Other Hardware 3rd Party Boards

6v6gt August 9, 2021, 6:27am 7

This should be volatile:

This should probably be INPUT_PULLUP :

You may have trouble using external interrupts to trigger the ATtiny85 when you progress on to using sleep modes. I'll try to find a reference.

Edit:

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Mysterious behavior of ATTiny85 and hardware interrupts

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