Copy the Code:

$$

const int ledPin $=9$; $//$ LED connected to pin $9$

int brightness $=128$; $//$ Initial brightness $(50\%$ duty cycle$)$

$$

void setup$()\{$

$$ pinMode$($ledPin$,$ OUTPUT$)$; $//$ Set LED pin as output

$$ Serial.begin$(9600)$;$//$ Start Serial communication

$$ Serial.println$("")$;

$$ Serial.println$("$Enter $\text{'}$B$\text{'}$ to set LED brightness $(0-255).")$;

$$ Serial.println$("$Enter $\text{'}$F$\text{'}$ to set blinking frequency $($in Hz$).")$;

$$ Serial.println$("$Enter $\text{'}$S$\text{'}$ to stop blinking."$)$;

$\}$

$$

void loop$()\{$

$$ if $($Serial$.$available$()>0)\{//$ Check if data is available

$$ char command $=$ Serial.read$()$; $//$ Read the command

$$ handleCommand$($command$)$;$//$ Process the command

$\}$

$\}$

$$

void handleCommand$($char command$)\{$

if $($command $==\text{'}$B$\text{'})\{$

$$ Serial.println$("$Enter brightness $(0-255)$:$")$;

$$ while $($Serial$.$available$()==0)$; $//$ Wait for input

$$ brightness $=$ Serial.parseInt$()$;$//$ Read the brightness

$$ brightness $=$ constrain$($brightness$,0,255)$; $//$ Constrain value

$$ analogWrite$($ledPin$,$ brightness$)$; $//$ Set LED brightness

$$ Serial.print$("$Brightness set to: $")$;

$$ Serial.println$($brightness$)$;

$$ Serial.println$("$Enter $\text{'}$B$\text{'}$ to set LED brightness $(0-255).")$;

$$ Serial.println$("$Enter $\text{'}$F$\text{'}$ to set blinking frequency $($in Hz$).")$;

$$ Serial.println$("$Enter $\text{'}$S$\text{'}$ to stop blinking."$)$;

$\}$

else if $($command $==\text{'}$F$\text{'})\{$

$$ Serial.println$("$Enter blinking frequency $($Hz$)$for $10$ blinks:"$)$;

$$ while $($Serial$.$available$()==0)$; $//$ Wait for input

$$ int frequency $=$ Serial.parseInt$()$; $//$ Read frequency

$$ frequency $=$ constrain$($frequency$,1,10)$; $//$ Constrain frequency $(1-10$ Hz$)$

$$ Serial.print$("$Blinking at: $")$;

$$ Serial.print$($frequency$)$;

$$ Serial.println$("$ Hz$")$;

$$ blinkLed$($frequency$)$;

$$ Serial.println$("$Enter $\text{'}$B$\text{'}$ to set LED brightness $(0-255).")$;

$$ Serial.println$("$Enter $\text{'}$F$\text{'}$ to set blinking frequency $($in Hz$).")$;

$$ Serial.println$("$Enter $\text{'}$S$\text{'}$ to stop blinking."$)$;

$\}$

else if $($command $==\text{'}$S$\text{'})\{$

$$ Serial.println$("$Blinking stopped. LED set to steady brightness."$)$;

$$ analogWrite$($ledPin$,$ brightness$)$; $//$ Stop blinking and set steady brightness

$$ Serial.println$("$Enter $\text{'}$B$\text{'}$ to set LED brightness $(0-255).")$;

$$ Serial.println$("$Enter $\text{'}$F$\text{'}$ to set blinking frequency $($in Hz$).")$;

$$ Serial.println$("$Enter $\text{'}$S$\text{'}$ to stop blinking."$)$;

$\}$

else $\{$

$$ Serial.println$("$Invalid command. Try $\text{'}$B$\text{'},\text{'}$F$\text{'},$ or $\text{'}$S$\text{'}.")$;

$\}$

$\}$

$$

void blinkLed$($int frequency$)\{$

$$ int delayTime $=1000/(2*$ frequency$)$; $//$ Calculate delay time in ms

$$ for $($int i $=0$; i $<10$; i$++)\{//$ Blink for $10$ cycles

$$ analogWrite$($ledPin$,$ brightness$)$;

$$ delay$($delayTime$)$;

$$ analogWrite$($ledPin$,0)$;

$$ delay$($delayTime$)$;

$\}$

$$ analogWrite$($ledPin$,$ brightness$)$; $//$ Return to steady brightness

$\}$

Lab Steps

Part $1$: Setting Up the Circuit

Assemble the circuit on the breadboard as described above.

Connect the Arduino to your computer via USB.

Part $2$: Understanding the Code

Discuss the role of Serial.read$(),$ Serial.available$(),$ and Serial.parseInt$()$ in handling user input.

Explain how analogWrite$()$ is used for PWM control.

Part $3$: Running the Program

Open the Serial Monitor from the Arduino IDE $($Ctrl $+$ Shift $+$ M$).$

Set the baud rate to $9600.$

Set Serial Monitor to $$No Line Ending$($right side of the screen$)$