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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 initialize an inputs been using bare metal code for our Texas

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Instrument team 4C 1 2 3 microcontroller.

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So these are the peripherals we have on our development board and we over here.

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We know where they are connected.

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Switch one is connected to peer for switch two is connected to PSU and we've got three entities from

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which copy this on and went to create a new project.

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So I've copied this.

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It's in my clipboard I pressed.

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I did this and then I press control SEE RIGHT WHEN to create a new project to buy here and create a

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food for it.

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I call this GPL your input

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and I'll quote a project to keep your input as well.

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And I'm going to select the board team for C 1 2 3 0 8 6 p.m. like this and then okay over here and

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then on the Simpsons going to select the core on a device I'm going to select the startup and then Okay

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I'm going to rename this to the name of the MCU.

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Tim 4C 1 2 3 0.

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H can forget about the other stuffs you h and I'll come over here rename this to application API like

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this and I'll come over here right click a new item I'll call it main name the C and I'll paste helping

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out here.

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Right.

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Okay so we can come to target options sets the X toward 216 sixteen megahertz debug dropdown over here

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select the SD link select the still areas I CDI come to settings and take this reset and round okay.

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And then.

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Okay so I'll include my MCU head by right clicking over here an include file this one here like this.

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Once that is done open up Main function into main over here like this open close and I'll start by initializing

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the clock.

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So what we're going to do is we're going to just recreate what we're going to create a simple experiment.

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When the push button push button lets a push button one is pressed we're going to turn on these red

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or green LCD.

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We can use the green lady for this example when we push button is pressed we simply turn on the green

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LCD.

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So let's start by initializing the clock access.

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Both are our LCD and our switches connected to switch is connected to P.F. port F so we've got to initialize

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clock access for Port F so come over here our GC

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GPI oh and then I'll do syrup X to zero over here

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and they will port f clock essentially once that is done we can come here see GPL you f

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and we can say FDA are over here we can say as your X your x 0 8 and this will initialize is who sets

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the green LRT as output and we can see this by just expanding your X or a two binary.

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So how serious or zero force year here and then perhaps you are one serious you here like this actually

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helps you one so I here this is bit zero bit one bit to be three.

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So this is P three right.

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Once that is done we can because P F one over here which is going to be because peer 4 which is going

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to be our switch one is supposed to be set as input.

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We need not do anything by default.

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The the pin has zero debt and to set to input you you have to write zero to that particular pin.

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So since we have not changed opinion its default status zero.

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We don't have to write anything into it.

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One other thing too is that our PINs here are normally high meaning without pressing that pin the pin

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state is high.

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If you read from the pin without the button being pressed it's high.

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When we pressed the pin that pin goes low.

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So we call this button an octave low button so to detect whether a person has pressed on the switch

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or the button we have to read low.

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If we read high it means it's not being pressed or it's in its initial state.

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So we've got to enable a pull up resistor for our push button to switch to and they would put up resistor

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we used to P R register.

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So before we do that actually let's enable them both as digital pins and went when say Chip GPL you

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f and I'm going to use the DP and register and I'm going to

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pass you x 1 8 over here and this enables both pins simultaneously.

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And I explained this and you see that it's corresponds to the pins we are interested in.

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So we have one here.

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This is serious it's one for the first name Beau in hexadecimal notation.

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Each digits here becomes four digits in binary right.

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And for binary digits or for binary numbers are known as a limbo.

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So if you hear someone say this the word if you had limbo like this.

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This of course for bits.

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So each digit here is known as a name though.

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Right.

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So when we expand this number here we get serious through a 1 in binary when we expand the 8 we get

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1 0 0 0 0 like this and we know this is bit zero bit one bit to be three and bit three here is set high.

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It's three SPF three criminality.

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And this is it's four bits four is P F four.

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That is our switch one over here like this.

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Okay.

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So this sets both of them to digital pins.

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Once they start and we can said they pull up resistor for our our switch sources GPI o f and then I'll

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use the P U R register and they will say is your X we passed one two here like this.

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So the stage was set up is complete.

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We simply need to read our pin state if it's pressed we turn on reality.

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If it's not we keep it off.

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So I'm going to open my while one loop over here open and close and I'm going to come over here and

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to read.

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I simply need to see whether the pin has become what as B has changed from zero to one because I said

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the pain is active low it's default status 1 so I'm going to do when do f over here of see if GP I O

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F and then data register and then I'm going to read the bits correspond into the pin which is Pier for

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here if data register value if the data register value it and I'll perform B twice and with 0 x 1 0

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and by passing you x 1 0 I'm performing between this and with this bit with the current value in the

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data register.

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So if this and this if this resort if this returns a positive result it means that pain has not been

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pressed because in an end operation if you perform logical end if two numbers are 1 the resource is

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1.

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If one number is 1 and the other is 0.

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The resource is 0 so if both numbers cause I've got one here as one up front and then the next up around

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it's going to be the corresponding bits in this data register.

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So if we take the corresponding bit and its value is 1 and then we perform a bit twice.

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And with this one here which is essentially this one here in binary and the resort is 1.

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This means they are both 1 if they are both 1 it means the switch has not been pressed since the switch

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is active low when we press the switch to switch value the corresponding bit here has to be low.

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So I'm going to see if this if this and this is not true I've put knots over here to indicate that if

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the resort is no one mean and if it's false then our switch has been pressed.

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And after that and we can see a GPI u a GPA you f we can turn on our D by saying data register and we

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simply turn on the LCD by writing 0 x page over here

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else we can write we can disable the LCD by saying ls

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we say GPL you f

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data register and we use the number sunshine over here and add to sign and to X 88 so that we disable

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just a bit we want to disable right.

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So let's rebuild and see what we have going to click over here to compile it's finished compiling.

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I'm going to click here to download onto my board and it's finished downloading.

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Okay so I'm going to press the switch one as press the criminality comes on I press it comes on and

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then it comes on.

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So basically we check in whether the state has changed over here and I hope you you understand this.

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If you do not understand the statement just send me a message by it's really simple.

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I'll put a comment here

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switches octave low right.

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So this all there is for this lesson.

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

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Have a nice day.