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Hello.

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Welcome back.

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In this lesson we're going to see how to set up the cystic timer to generate an interrupt at a fixed

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rate.

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We're going to set up our cystic timer to generate an interrupt once a second meaning it's period or

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its frequency is going to be 1 Hertz and in the interrupt service routine.

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We're going to blink out early.

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And over here we're just using the LTE blink as an example of a task that can be performed within the

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interrupt service routine.

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But in your know more and better development applications you can create the cystic interrupt and place

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a piece of algorithm there a piece of algorithm that you want to be.

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You want to execute periodically.

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This can replace the LCD blinking function that we shall be right in there.

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So the interrupt service routine can be used for anything.

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Just that in this course we simplify things by using LCD to demonstrate everything but really the melodies

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can be replaced with your own algorithms your own output devices.

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And in fact your own input devices you can read send source when the interrupt occurs without talking

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much less create a new project and see how this is done.

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Come over here.

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You Vision project create a photo for it.

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I call this cystic interrupt

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quote a project cystic interrupt.

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I'll slip my board here.

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Tim Fauci 1 2 3 issue of age 6 p.m. and then I select this and then okay on a census I select the call

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on the device or select the starts up and then okay over here once that's done I renamed this to the

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name of the board.

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Team Fauci one two three.

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And then I'm going to extend this.

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And so this group here going to rename me to AP

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and then I'm going to come over here targets options are set up to 16 and then debug group down.

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Still there is ICD I can then click over here and then take research and run and then okay and then

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okay I'll come over here right click out new item to group main and then I'll give the file a name.

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Right now stop by including the port header.

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It's this over here.

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Now jump straight into it into Main and when stuck by initializing our early.

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I'm sure you're used to doing that by now.

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Come down here I'll see system control of CTC GPA.

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And then this course because we sat in Port f we pass your extra it's your excuse you're over here.

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And once that's done we're going to set all of the D GPA to f direction register gonna pass sir x.

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Sure.

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E over here and this is set or the LCD outputs.

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And we do a GPA you have

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to enable

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this your ex your E over here.

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And then we said all of them are stitch two pins.

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Once that is done we can configure to cystic put a comment here for you.

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Okay let's begin by disabling global interrupt whenever you want to enable interrupt or set up an interrupt.

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You first have to disable interrupt globally and we do that by using underscore underscore disable AI

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our cue like this.

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So would you say would interrupt and I'm going to start by loading the cystic

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cystic access to load register over here load and this of course 16 million.

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One two three.

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One two three minus one like this.

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Once that is done we set the system control register we enable cystic through any control register cystic

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and then control and then we pass them a seven here.

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If you expand this you realize that this corresponds to that bit that would enable cystic.

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And then use interrupt and use system clock.

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Right.

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So this what all of that is encapsulated into seven over here.

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So this what we need to do actually.

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So once this is done we've got to enable interrupts globally and we do this by saying e and i are queue

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like this.

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And once that's done we can come over here while 1.

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And then we'll have nothing in our while one loop because our blinking is going to happen in the cystic

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handler to the cystic unless a callback function.

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The system would recognize this automatically.

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It's called cystic Floyd cystic underscore handler and we'd need not put the prototype up because it's

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a callback function.

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We don't have to copy and put it prototype on the top here.

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The system would recognize this automatically.

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So in the cystic handler we want to perform our competition.

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It could be performed digital filtering it could be you could perform your fire filter or DSP algorithms

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over here or if you are creating a real time candle you can you know invoke the scheduler over here

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to switch to the next task.

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But in our example we simply going to toggle an LCD in the system handler for those who you taken my

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other course on creating your own real time operating system.

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You remember that we use in this cystic handler arsenic time these basically this they can't let that

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you know control is a what scheduler to move from one task to the other.

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But over here we simply blink an analogy or toggling an entity to we do that by saying keep you f data

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register and we are going to read a lady bypasses your ex your two over here like this.

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Right.

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So let's build and see or click over here to build.