Worksheet1_API.md

~~~
title: "Session 3:  Worksheet 2"
author: "Dan Goldsmith"
~~~

# Brief

For this task we are going to make use of the MBED API, to improve the
code we are writing.

Imagine we have been asked to write code to drive a light bar.
there are 4 LEDS that flash in a sequentail pattern.


|         | Led 1 | Led 2 | Led 3 | Led 4 |
|---------|-------|-------|-------|-------|
| Stage 1 | X     |       |       |       |
| Stage 2 |       | X     |       |       |
| Stage 3 |       |       | X     |       |
| Stage 4 |       |       |       | X     |

\clearpage
## Initial Code

We could write code that looks like this

~~~ c
#include "mbed.h"

DigitalOut led(LED1);
DigitalOut led2(LED2);
DigitalOut led3(LED3);
DigitalOut led4(LED4);
int main() {
    while (1) {
        //Blink in an offset pattern
        led = 1;
        led2 = 0;
        led3 = 0;
        led4 = 0;
        wait(0.5);
        led = 0;
        led2 = 1;
        led3 = 0;
        led4 = 0;
		wait(0.5);
		led = 0;
        led2 = 0;
        led3 = 1;
        led4 = 0;
		wait(0.5);
		led = 0;
        led2 = 0;
        led3 = 0;
        led4 = 1;
		wait(0.5);
    }
}
~~~


## Task

However, its not the cleanest design.  If we look at the MBED API
<https://os.mbed.com/docs/mbed-os/v5.11/apis/index.html> , it appears
the BUS interface is appropriate to use here.

Read the Bus API, and reimplement the code making use of this functionality.