Using ARM cortex m$4$ assembly:

Part one $(0\mathrm{.}3$ points$)$: Write a program to increment the value in register $0$ by one each time

the button $($PA$0)$ is pressed $($input goes from $0$ to $1).$ Don$$t debounce. When testing this

code, press the button twenty times and see how many presses are counted. Don$$t be

surprised if the count is sometimes greater than twenty due to single presses being double

counted due to the lack of debouncing. Don$$t forget to initialize the button.

Part two $(\mathrm{.}8$ points$)$: Fill out the code below to do as each comment requires $($you$$ll need

more than one line of code per comment$).$ This code will go in your $\_\_$main section. For the

delay loops, you may need to experiment with the starting value from which you subtract

$($see April $1$ lecture$).$

;initialize PD$12-15($output$)$ by calling initialization subroutine

;turn off all lights to start $($this can be in the initialization$)$

;turn on only PD$12$

;delay$/$wait ~half a second using a delay loop

;turn on only PD$13($turn PD$12$ off$)$

;delay$/$wait ~half a second

;turn on only PD$14($turn PD$13$ off$)$

;delay$/$wait ~half a second

;turn on only PD$15($turn PD$14$ off$)$

;delay$/$wait ~half a second

;turn all lights off

;delay$/$wait ~half a second

;start the cycle again with PD$12$ on$,$ then wait, etc.

Part three $(1\mathrm{.}2$ points$)$: write a program that loops through a null$-$terminated read$-$only byte

array called Numbers and displays each value on the lights. Each value in Numbers can be

between one and fifteen inclusive $($with a $0$x$00$ at the end of the array, of course, as it$$s

null$-$terminated. This will be shown on the LEDs with bit $0$ being represented with PD$12,$ bit

$1$ with PD$13,$ bit $2$ with PD$14,$ and bit $3$ with PD$15.$ You$$ll move to representing the next value

in the array after the button $($PA$0)$ is pressed and released $($goes from $0/$unpressed to

$1/$pressed and then back to $0/$unpressed$).$ After displaying the null$-$termination character,

start the array again from the beginning.

Example:

If the Numbers array is $1,12,9,14,0$ then the PD$15-12$ will be off, off, off, on$,$ respectively,

to represent $1$ as binary $0001.$

After the button is pressed and released, PD$15-12$ will be on$,$ on$,$ off, off to represent $12$ as

binary $1100.$

After the button is pressed and released again, PD$15-12$ will be on$,$ off, off, on to represent

$9$ as binary $1001.$

After the button is pressed and released again, PD$15-12$ will be on$,$ on$,$ on$,$ off to represent

$14$ as binary $1110.$

After the button is pressed and released again, PD$15-12$ will all be off to represent $0.$

After the button is pressed and released again, PD$15-12$ will go back to $1100,$ as that is the

first value in the array, and the cycle will repeat.

Hints:

$$ Use the initialization subroutines for GPIO that we$$ve already written

$$ You$$ll need to debounce the button presses by putting a delay between IDR reads

$($see the April $5$ lecture for more$)$

$$ Since bits $3-0$ of the value correspond to GPIOD ODR bits $15-12,$ you can use shifting

to help turn the appropriate LEDs on$.$ Just make sure to turn off lights you won$$t

need.