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Hello.

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Welcome back.

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So in the last lesson we saw how to develop a what.

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You drive up.

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We created the GPL you as an output and then were able to turn on the LCD.

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Now let's see how to make the LCD print blink.

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I should say I am going to create a copy of the last project and rename this and then we just continue

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from there.

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You can open it

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right.

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It's opened.

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So we are going to create a delay function to help us do this.

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And I should mention this delay that we want to create is not precise.

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Later on when we get to the section on time is we going to see how to create precise delays.

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But for now I'm going to create delays I'm going to create our say pseudo delays.

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Actually I shouldn't say it's not precise.

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This delay is precise but it is calibrated for my my particular configurations and what I mean by this

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is it is calibrated for my MCU running at 60 megahertz and using the call you efficient compiler.

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So let's see what I mean.

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I'm going to create a symbolic name for one second.

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I'll call this one sec.

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Q You and I'm going to sign this constant so I'm gonna pass this to my register and we're going to keep

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minus in one from this taken one from this.

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And by the time it reaches zero one second would have passed and then I'm gonna create another symbolic

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name.

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This is half a second and I'm gonna use this.

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I'm gonna use half of this value here which is this.

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Right.

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So then we can go ahead to create our daily

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come down here to create a new subroutine called delay

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come here and then I'll see a delay

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in this This subroutine shall take the contents of register are three so we are going to part of what

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delay amounts.

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Our argument is gonna be placed in r 3.

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So I'll come here and see sup is

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R three are three and then minus one meaning subtract what is an R 3.

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So product 1 from the content of our 3 input I resort back into our 3 and then I place the S over here

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because I want to update the PSR flags when I perform this operation to subtract operation and the reason

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I want to up date the flags is that I want to be able to check what I knew of the flux I set the PSR

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flags for those of you who took day the fundamental course the assembly program from ground up we spoke

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about those flags we have this zero flag the carry flag the overflow flag so the Zero flag is set when

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the previous instruction or the previous operation return the result of zero.

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So that flag is gonna be set right.

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So I'm gonna say B and E GONNA SEE A B and E delay

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and this basically means branch if the Z flag is not equal to zero

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meaning if doesn't like you said if the result here if the result here is is zero.

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If we keep subtracting from our three if we keep subtracting one from this number and we end at zero

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the Z flag is going to be set.

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So we check if there is if like you said if it's not set then let's keep subtracting.

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If it s not set we keep subtracting.

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That is why we seem branch if the C flag is no set meaning we've not arrived at zero yet

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and then I'm going to return from the subroutine by doing B X LR like this.

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Right.

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So I'm going to write a new subroutine known as Lady blink and then I'm going to test all the delay

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function to

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so we start off by accessing our data register

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I'm going to access the data register like we did before

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so we have the data register now we've accessed it read We put in our zero and then we turn reality

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on this what we do we did this already.

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This is our entity on once the LCD on we're going to load one second I'm going to do load R3 with the

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constant one second

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and once we floated our three we're going to branch two hour delay subroutine

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and then we going to turn reality off or just copy this

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I'm going to create a symbolic name for 10 in the early days off.

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I'm gonna have red off here.

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Red is bits number one so red.

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So red off I'm gonna do

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red off equals shift zero to position one like this I'm gonna take this red off

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and put it here.

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So we're gonna turn red off and we're gonna delay again.

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So start by loading R3 with one second again and then Bill

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then we delay.

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We go to a delay on subroutine and then this is it.

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We can we can keep a branch into the top so that we create a loop here.

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Lady blank over here like this so now we can try this out.

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I'm gonna copy this label and come over here and because we already have a lady playing us a loop we

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can take out this loop.

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Okay we can test out our code and see what we have.

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I'm going to click here to build

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have an arrow here.

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It says one sec not defined

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okay there's a typo here

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okay.

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Let's do it again.

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It's built successfully.

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I'm gonna click it download it.

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Mm mm mm mm mm mm mm mm.

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I'm gonna download onto my board by clicking here.

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It downloaded.

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You can see the LCD is blinking at a rate of one second.

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Right.

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This all the risk for this lesson.

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Like I said distillate is not perfectly precise.

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This is sort of calibrated as to um you can just take it as a pseudo delay but this is how we are going

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to make our lady blink.

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Um when we get to the time of section we going to see how to create delays using assisted time is as

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well as general papers time is but for now this all the rest.

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If you have any questions just let me know and I'll see you later.