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Welcome back.

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In the previous lecture, you learned how to read the state of the button in the simplest possible way.

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As you can see here, we just use a while, true infinite loop.

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And in it we just take a reading of the button, fairly painful, and then act accordingly.

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The problem with this method, of course, is that you've got an infinite loop here that looks at the

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execution of the program in it.

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It's not a very efficient way to use your hardware.

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In this lecture, I want to show you an alternative which is more efficient and allows us to read the

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state of the button using a hardware interrupt.

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So in this line here, line 58, I have to find an IQ and interrupt request on button painful and have

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configured it in a way that is very efficient.

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So what I'm saying here to the trigger is the falling edge of the signal that is produced by the button.

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So when you press the button, the voltage on your full force from high to low, and that is the IQ

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falling edge which is detected in triggers this interrupt.

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And when this edge, the falling edge is detected, then they interrupt.

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Is calling this routine here a function, the button and this compressed underscore ESR interrupted

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service request or retain his ISO, which branches the program inside this function and again act accordingly.

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Will get to this in a minute in order to display the ality lighting up.

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When I press the button, I'm still using a while loop here.

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It's just the easiest way just to demonstrate the interaction between an eyesore and then a different

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part of your program.

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And I'm also demonstrating the ability of Intisar and other parts of your program to communicate using

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global variables in this case.

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Now let's have a look at some of the details.

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You can see up here in line 36, I am importing the PIN function, disable IQ and enable IQ functions

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from the machine module.

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And again, the slip in there from the time module.

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I'm starting by creating the object as usual, and then the pattern object, which is exactly what we

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did in the previous example.

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Same thing here.

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Nothing has changed.

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Then I'm declaring a couple of variables.

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This is the button pressed portable.

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It allows the IQ routine of the ISIS recorded here, retained to communicate with other parts of my

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program.

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So when a button is pressed, then I update this variable here.

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You can see it is updated here and then used here to determine whether they should be turned on or off.

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They also have integer like a numerical variable here that keeps track of how many times have pressed

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the button before it's reset.

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So you can play around with those variables as well.

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Now, inside the definition of the routine that we will be called by the IQ, you can see that it requires

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one parameter.

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And this is the object that has caused the IQ and this is passed by the IQ routine here as well.

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And I'm using this object here to print out some information about what is it that has caused the IQ

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to see I'm taking PIN and exactly what it is and passing it into the button pin global Viterbo, which

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is then printed out down here so I can get some information about the object that caused the IQ.

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A couple of other interesting things that are happening in here is, first, that I am calling the disabled

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IQ routine, which, as you can probably guess, will disable further excuse.

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So when I press the button, the first thing that happens with disability IQ, while the Isar function

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is busy, any further button presses will just be ignored until I re-enable the IQ right at the bottom

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of the isobutane.

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So when I'm done doing whatever needs to be done to deal with the existing IQ, then I will re-enable

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it so that the 32 can detect the next button.

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Press a couple of other interesting things here that are perhaps a bit unusual for you is that I'm using

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the global keyword here so you can see what's happening, of course, available, such as Button Pressed,

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which I have already declared at the header of my program.

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So you would expect that this variable would be global already just by the fact that it's been declared

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the header of the program, but in fact, it isn't.

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I won't be able to make any changes to this variable from inside this context before I use the global

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keyword to convert it into a variable that I can make changes to.

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I've got a link for more information about this here.

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If you're curious about how this works, if you don't use this keyword, then you are going to get a

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syntax error or you're going to get an interim message on line 53 when you try to make a change to the

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value stored in this variable.

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So do the same thing with the other two variables that I'm using across different sections of the program.

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So button spin and press count, you can see that all of those have been declared up there.

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And I still need to use a group of able to be able to make changes to them.

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All right, so then I just store to the button, pressed as to the object that is causing the IKEA into

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button pin and then I increment the press counter to what?

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And then I close the cube in here.

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You've got the infinite loop, which is similar to the loop function in the Adreno is just constantly

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going around executing whatever codes you have in it.

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And in this case, it's constantly checking for the value stored inside the button pressed variable.

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And when it's true, you will go inside, change it into force, turn on the ality, print out the two

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messages zero.

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The counter will reset the counter and keep the lady on for half a second.

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If it's not true, then it will turn off the reality and that's about it.

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So I am going to save a copy of this program to make replacing it with PCs and it's going to hit control.

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See you stop the execution.

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All right.

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And then try again, save a copy of Python and you can call this.

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I tend food interrupt why?

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All right, how close these two and not that one, I need to open up the interruptive position, but

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program this one right here.

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And now that I've got the program opened on the target market Python device, I will play it.

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And.

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Press the button and works.

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Stays on for half a second as well.

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Right.

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And one thing to notice here is that in the message that starts with Button pressed at it right here,

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you can see that the output of button pin, which is this variable here, which contains the object

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that has caused the interrupt, it says painful that way.

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If you have multiple interrupts from different areas, then you can always differentiate as to which

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button or which interrupt is the one that has triggered your interrupt service routine.

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OK, so that's about it with the bat, an example using the hardware interrupter.

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I want to show you one more variation of the same in the next lecture, which involves this time using

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a timer interrupt this ticket out.