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Hello, welcome back and this lesson, we're going to see how to work with mutex, I'm going to make

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a copy of our last project.

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The project in which we created the drive is the project here called Some Drivers.

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I'm going to copy this copy and paste over here and I'll rename this to SEMAFO Mutex Twenty on the SEMAFO

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Mutex.

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It's called Pean.

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We had done.

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OK, so this is 20 I'm going to open may not see over here, right?

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So we're going to create an application similar to the one we had in our binary semaphore project.

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I'm going to open one may not see over here.

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We already have our ADC SDI files included, so we need to include them over here, the digital read.

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And since I read, we're going to come into this out.

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Or we just cut it out later, so less great, we going to create a simple application that has a number

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of tasks, there is going to be.

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There's going to be two tasks.

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One task will be for the digital sensor, which is our button, and then another task is going to be

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for the analog sensor, which is our ADC that we've created or with initialized.

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So I'm going to start off by first creating a semaphore of semaphore here.

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Remember, a mutex is a type of semaphore.

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So it creates a semaphore handle.

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Yeah.

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Called Zero SEMAFO.

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And this semaphore is going to be used to access the serial port.

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Each of the task we need to acquire this semaphore in order to be able to access the serial port.

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So once I've done this, I'm going to just start by printing system initializing.

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Like I said, we're going to use this to make sure our you know, what is giving us problems when something

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is not working.

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So once this is done, we said the system initialize in.

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And once that is done, we're going to create the mutex semaphore.

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Like this, we simply see eczema for Cretz mutex and then the handle is going to be stored in a variable

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that we declared up here, OK, once that is done, we're going to create two tasks.

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The first task is going to be for the digital sensor, as we said.

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So this task is called digital sensor task.

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That's the name of the task function.

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We simply call this bottom reed and this is the stack size.

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You can make the stack size 100.

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It's fine.

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And it's quite a priority.

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Off to the next one is going to be the the one for the analog sensor.

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So we simply call in this sense or read and a task function is going to be called analog sensor.

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And we've given this a priority one over here.

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The priority really doesn't matter.

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We can use in a priority configuration, as we shall see, but the reason is for who starts first.

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So we would experiment with that.

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OK, so once we've done this, we would start the scheduler.

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By simply calling our V Task Start scheduler.

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So once that is done, we can go ahead and implement the task functions.

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We start off with the.

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The task function for the digital sensor, so I'll come over here.

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It's called Digital Sensor Task Open, Close, and then our infinite loop in here like this.

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And then we have one for the analog sound, so.

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Open, close, and then our infinite loop here like this.

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So actually, inside our digital central task, we can initialize our GPU there, so cutaway you in

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it.

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And then bring it inside digital sensor over here, not in the infinite loop, but we want to run this

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once, so we put it in here.

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And then we're going to initialize the ADC in the analog central task, so cut this.

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And then I'll bring it down here.

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Like this, OK, so once this is done.

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In our digital sense or task, we going to read the bottom states, so this line that we had previously

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beaten states, of course, read digital.

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So I'm going to cut this.

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And then I'll put it in our digital senso.

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And then.

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Over here, you our.

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Analog Senseor.

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I'll cut this and put it in our analog or task such that each Senso, each task reads its own Senso.

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OK, so so each task would read it senseor and then the task would try to grab the SEMAFO grab to try

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to grab the semaphore.

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OK.

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SEMAFO.

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We see.

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If ximo for take.

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And then we basically call in our semaphore take function, we pass the SEMAFO Hondo here, and then

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the amount of time over here, we are checking if it's true.

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So if the SEMAFO is not available, wait five ticks for the scheduler to see if it becomes free.

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So, wait, five takes off the schedule, are we using ticks here?

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We've not converted this to milliseconds.

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This is fine.

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So we're saying if it's not available, wait for five ticks and if.

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If it's not available, wait for five ticks, OK?

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And if you receive it, then print this, you know, a zero port.

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Right, if.

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If this is true, meaning you've been able to take the semaphore, then this block will print.

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And then over here, we can put a bit of delay for stability, OK, task.

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DeLay one year like this.

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OK, so.

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Once we've done that, we have to give the semaphore, remember, I said in the in the binary some of

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what I said, there is a way that we can take the semaphore without giving it.

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Well, this is not the method over here, although it is called a mutex semaphore.

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When we take it, we still have to give it.

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It's not.

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So still, we use our semaphore teak and semaphore give.

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I know I mentioned there's a way to use one function rather than use both take and then give.

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This is not the method.

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OK.

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So once we've done this, we're going to give the semaphore, remember, you've got to give the symbol

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for using our bathroom analogy once you've taken the key to enter the bathroom.

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You have to retain the key.

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So we give the SEMAFO so any other task can take the SEMAFO and use the support as well.

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The only difference between this and the other one we had is we declared this as semaphore creates mutex

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OK, so once this is done, we're going to use the same method for.

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Our analog.

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This is our analog task.

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We take the SEMAFO.

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We have this over here.

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And then.

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Sorry about that.

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So first we read the census data, we store it in its variable, and then we take the SEMAFO.

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And then once we've taken the semaphore, we're going to print this and so value.

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We simply prints of value because now we have access to the, uh, the Ewart's, we can print the sense

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of value and then we give the semaphore.

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Like this.

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In here, once that is that we can add V task, delay one for stability.

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OK, so this one, we have digital sensor task.

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Takes and then its uses it and then gives and then this one takes, except that this time we use an

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actual ADC values and the button state.

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OK, so this is what we have.

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What we have to do is take our function prototypes to the top.

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I'll copy analog since I taught, uh, task over here.

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And then we do the same for digital sensor task.

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Right, so we're looking good.

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OK, let's build and see what we have a click over here to build.

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OK.

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Over here, we have an error and then a couple of warnings error.

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First it says, OK, we've not included our semaphore at age four, so we've got to include that.

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So I'm going to come over here to Simms's storage open declaration and then.

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I'll come over here and say include.

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It is spelled s e m p h r, I think that the H.

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OK, let's run and see, perhaps the E is not required.

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OK, no error, so the spelling is good, this is the name of the semaphore file to these errors, these

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warnings, as I specify, a full percentage.

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So I'm going to make this percentage L.

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D and over here, percentage L d that's run and see.

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Dispute what, as I say, one zero one warning.

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The warning.

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Let's see what I say, percentage go the expect argument of long and.

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OK, what was the first warning then, control s.

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And control is.

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Let's see what data types do we have here?

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We have you and.

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OK, 32 and you and eight run this.

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And we have one warning I see this is the sense of value.

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For much percentage, the expected argument of end.

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OK, so I'm simply going to change this to I can type can start to end or change this to enter simply

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it doesn't make a difference here.

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Click over here to build.

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OK, we have no one in.

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OK.

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OK, so I'm going to open real time.

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I'm going to select the port, not open this port on the side, and then I'm going to right click and

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then I'll see.

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Debuggers, ASTM 32 and then iSelect number 20 here.

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And then OK.

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It's open in SWICH.

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And then side by side.

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I'm going to click to run over here like this.

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OK, as you can see, we get to know.

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Our sense of value as well as our partner states, I'm going to press the button and you can see where

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we see zero our exits to the other side.

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So if I move it, you will see the value change as well.

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But you can experiment that on your own.

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OK, so this is how our mutex is allowing us to access the single resource, which is why you out in

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an orderly manner if we comment out the semaphore taking some of Augier functions.

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We realize that the data will be jumbled up in the display.

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OK.

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So.

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Like I said, the the the priority really doesn't matter here we started with digital sensor hub in

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a priority of two.

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OK, we have to set this up, but before we go, I will show you a difference, the difference between

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this one, the difference between a SEMAFO create a creating SEMAFO in binary.

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Some of what we had you realize that over here we didn't have to give the SEMAFO.

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You see, when we created the SEMAFO, we didn't give it, the first thing we did was check if it's

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available, whereas in our binary semaphore we had this issue, we had a deadlock.

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I'll show you this is how binary some of our projects are.

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Click over here to open.

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And then I'll open the door, may not see for.

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It's open in a computerized behave in slow.

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OK, so this is how binary SEMAFO.

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You see over here, we had to give the SEMAFO in a way like basketball, someone has to toss the ball

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in the air so that one team will grab it over here.

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We had to give the SEMAFO before we take it.

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Right, but when we create it as a mutex, we need not do that.

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Over here, we didn't give the some of what we simply took it.

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OK, so we said the the priority here has no difference.

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So I'll just set this also to priority one.

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So they both have the same priority of one less run and see if it makes a difference to be able to build

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within.

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And I'm going to download onto the board by clicking here.

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Then click to switch.

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OK, so I'm going to run the code, click over here to run.

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Going to open our ports, as you can see, it's working the same way, pressed the push button and as

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you can see, we are reading about zeros.

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OK, right, so that's all there is for SEMAFO Mutex you have any questions, leave them in the questions

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and answers area and I'll see you later.

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Have a nice day.