Interrupts are an efficient way for a program to be able to respond immediately to a specific event. In the previous article I explained the basics of using interrupts in RPi.GPIO and gave an example of a simple “wait for an event” interrupt program.
In this second article I will introduce “threaded callback” which opens up a lot of new possibilities.
So What are we going to do now?
We’ll keep most of what we did before and add another button and an event detect threaded callback that runs when the new button is pressed, even though we are still waiting for the first button to be pressed.
But this time, the new button will connect GPIO port 24 to 3.3V (3V3) when pressed. This will allow us to demonstrate a rising edge detection. So we’ll be setting up port 24 with the built in pulldown resistor enabled.
Later on we’ll have to modify the code to cope with ‘button bounce’, but we won’t say any more about that just yet.
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