Task 1: Modifing Code to use Functions

Consider the following code

DigitalOut led(LED1);

int main() {
    //Flash LED  5 times
	
	for (int x=0; x<5; x++){
		led != led;
		wait(0.5)
	}
	
	//Flash LED 10 times
	for (int x=0; x<5; x++){
		led != led;
		wait(0.5)
	}

First lets break this into a function. This would let us reuse the code in different places in the program.

The questions we need to ask:

What chunks of code are reused
What variables are in the reused code?
What parameters would we want to pass to the function?

The Reused code is the part in the loop

	for (int x=0; x<5; x++){
		led != led;
		wait(0.5)
	}

In this example, the number of times we blink the LED is a good candidate for a parameter

Function Definitions

Take for form Return Type Funtion Name (parameters)

Return Type we dont need to return anything, so void is good
Function Name Something sensible that descibes the functionaly
Parameters Number of times to repeat (an integer)

void flash(int repeat){
   // Function Body goes here
 }

Therefore our function code ends up as

void flash(int repeat){
   for (int x=0; x< repeat; x++){
		led != led;
		wait(0.5);
   }

Calling the Function

We can now call the function by using its name and supplying any parameters.

int main() {
    //Flash LED  5 times
	flash(5);
	
	//Flash LED 10 times
	flash(10);
	}

Your Task

Extend the function to take the delay time as a parameter.

Task 2: Getting Classy

To turn the function into a class we need to consider the attributes and functions.

I this case we have a couple of potential pataeters

pin electronic 'pin' the LED is connected to
delay how long to wait betwen toggling modes.

There are also candidates for functions

flash Actually do the blinking.

Implementing the class

Standard CPP class definition, note the use of initialisation list for the pin as it is an object.

#include "mbed.h"

class Flasher{
    private:
        float delay;
        DigitalOut pin;
        
  public:
     //Constructor
     Flasher(PinName thePin, float delayTime) : pin(thePin) {
         delay = delayTime;
	 }

	void flash(int times){
	    for (int x = 0; x< times; x++){
    		pin= !pin;
	    	wait(delay);
	    }
	}
};


int main() {
	//Setup
	Flasher ledOne = Flasher(LED1, 0.5);
	Flasher ledTwo = Flasher(LED2, 0.25);
	
	//Loop
	while(1){
		ledOne.flash(5);
		ledTwo.flash(10);
	}
}

Task

Modify the Flasher class to take account of Multiple Lights.
Add functions for the State to the Flasher Class
If we have time, implement the button press to change state.

NOTE: Each set of lights will work independently. We need some form of multi tasking for both sets of lights to work together. We will be looking at Concurrency over the next couple of days.

KPIT_MBED_worksheet/Topic2/Worksheet1_ClassyFlasher.md