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Hello.

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Welcome back.

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So I said mention in the next two lessons we are going to see how we can use timers to count the occurrence

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of events.

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And we are also going to see how we can use timers to measure the time between two events occurring

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and to do that.

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I'm going to bring you over here to politics and dot com.

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This the official website for this cortex AMC which you watching were written a couple of articles on

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this Web site for this particular topic which I'll be treating today.

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So just type cortex and dot com hits enter you'd come to the cortex and page you just go to lessons

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and we've got the we've got free lessons.

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And part of those free lessons are the lessons that we are interested in.

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So to demonstrate how how time is used to current events we going to take a case study approach right.

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And we have a very nice example here when you come here you select count and event.

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There is this nice blog post that explains everything in detail.

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We will read this first.

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I'll explain how it works and then we go back to your vision and then write the code.

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Show us the title of this post it says.

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It says use in time is to count parents of an event.

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And I'll just do a bit of reading here.

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Taking you back to the old days in a classroom.

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So do part and media as we discussed in the lesson on creating delays using time as timers are usually

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used to perform three kinds of tasks creating delays counting events and measuring the time between

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events and the previous lessons.

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We looked at the basics of time as how to find a time interval value based on the frequency of your

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microcontroller.

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How to create delays in units of microseconds milliseconds and seconds.

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We also explained the meanings of the various time configuration modes such as 16 bids 32 bit up now

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counter etc. If you are not familiar with these topics please go back and watch the previous videos.

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That being said in this lesson we are going to talk about the second use case of time as that is counting

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events.

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Events are detected by signal or voltage level transitions.

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For example when a switch connected to a microcontroller as an input is pressed the microcontroller

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detects this press action because of the signal changes that occur are the pin as we can see in the

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diagram below.

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One leg of one leg of the pin is connected to DC 5 vote and the other leg is connected to the microcontroller

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pin.

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When we close the switch the microcontroller pin receives high signal which in this case is DC five

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votes.

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When the switch is open or is off the microcontroller is disconnected from the DC 5 board.

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Therefore it goes back to low.

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So this is the arm.

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This is basically how switches are detected and this is how events are also detected in microcontrollers

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and various computing applications.

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Now let's look at the difference or less elaborates on rise in age and fallen edge because these are

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the two main characteristics used in decision making.

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The transition of the signal from low to high gives us the rights and age and the transition of a signal

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from high to low gives us the fallen edge.

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Besides we move from DC 0 vote to DC 5 vote by rising and move from DC 5 votes to DC 0 vote by.

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Hence the name rise in age fallen age.

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It is quite important to grasp this concept because this is how we really can't.

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The occurrence of events and also calculate the duration of a particular event.

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In this lesson we used a switch as an example because it is the most basic inputs component.

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However the principle works the same way for all other components such as sensors and external logic

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gate.

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We connect to our microcontrollers.

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Let's look at a use case.

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Let's say we have design in a system that counts the number of people passing through airport security.

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We can design a simple low cost people's counter.

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If you meet with a single laser light and a light dependent resistor and a microcontroller Of course

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all we need to do is decide on where we want the cross line to be Place.

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Place the laser light on one end and the light dependent resistor connected to our microcontroller.

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On the other hand depicted here we have the laser light emitting this red laser light and then we have

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the oh the are the light dependent resistor here connected to the microcontroller.

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So in this very simple example when you turn on the laser light make sure it is pointing exactly on

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the head of the light dependent resistor.

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Remember the light dependent to resist that it's a light sensor.

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Changes resistance based on the amount of light shown on its head because we are not interested in calculating

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the amount of light.

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We simply said the microcontroller pin of our LTE R as a digital input pin.

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Now it's basically becomes the switch we discussed earlier when the path of light between the laser

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lights and the LDA are is broken which will happen when people cross.

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When people walk across the laser light the voltage at a microcontroller inputs being changes and this

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change happens in the form of rising edge or falling edge depending on how you connect the LTE are whether

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to G and D or to DC fivefold.

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We can count the number of these changes to determine the number of people who have crossed the line.

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So this an excellent example on a very demonstrative way of using time is to count the occurrence of

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an event and we have this little note here it says what this system is not entirely foolproof.

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For instance when two people walk side by side it will be difficult to count them both.

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How ever we hope it provides sufficient explanation on how counting works.

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So basically you can come back to this article and take a look at it.

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And if you have further questions just live in India and the question is sections below and in the next

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lesson we will take a look at how to set up our time off for and events and then after that we go to

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you vision to write the actual code.

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So see you in the next lesson.