$(25$ points$)$ display.c : handles all display to the LED array. It will need a global variable with type pi$\_$framebuffer$\_$t$*.($in C$,$ "global" variables are scoped only to the file in which they are defined unless other actions are taken$).$ Should have at least the following functions:

void open$\_$display$($void$)$: allocate the Pi Framebuffer device and store in a "global" variable for later use. This function should only need to be called one time when the program runs.

void close$\_$display$($void$)$: deallocate the Pi Framebuffer device $($if it exists$)$ and set the storage variable to NULL. Be sure this does the right thing if called before openDisplay$()!$

void display$\_$letter$($char letter, int xOffset, int yOffset$)$ : draws the provided letter on the LED array oriented so that "down" is towards the joystick, but shifted to the right by xOffset and down by yOffset. Note: the only letters you need to be able to draw are the capital initials of all partners in your group $($you should be able to use what you figured out for the "monogramming" assignment$).$ If any successive pair of letters would be the same, substitute a $\text{'}3\text{'}$ for one of them.

void clear$\_$display$($void$)$ : clears the display

$(25$ points$)$ input.c: will handle all interactions with the joystick. It will need a global variable of type pi$\_$joystick$\_$t$*.$ Should have at least the following functions:

void open$\_$input$($void$)$: allocates a joystick device and prepares to accept input.

void close$\_$input$($void$)$: deallocates the joystick device and set the pointer to NULL. Should do nothing if the joystick hasn't been allocated.

void check$\_$input$($void $(*$callback$)($unsigned int code$),$ int delay$)$: checks whether the joystick has recorded any inputs $($using pollJoystick from the sense library$).$

That first parameter declaration looks really weird: it means "the parameter is named callback, and the value will be a function needing an unsigned int parameter and having no return value". Note that the argument should be the actual function, not a function call! You'll use the function handler described below under main.c$.$

The second parameter $($delay$)$ is a time to wait in milliseconds $($actually$,$ about in "double milliseconds" on my Pi$).$ You can use this as one way to modify the speed of the scrolling, but see "A Note About Velocities" below!

$(5$ points$)$ scroll.h : prototypes for all the above functions for use in main.c below.

$(25$ points$)$ main.c : contains the following functions:

void handler$($unsigned int code$)$: the callback function for the joystick. When the joystick is manipulated, this function will be called with a code indicating what kind of manipulation occurred. It will need to adjust various global variables to adjust the behavior of the program.

int main$($void$)$: arranges to set up a display and joystick by calling functions from above. Will call check$\_$input and display$\_$letter repeatedly until the program should exit. The arguments to both will depend on what has happened with the joystick.

$(20$ points$)$ a Makefile with $($at least$)$ the following targets

Rules to compile $.$c files into $.$o files $($input$.$o$,$ display.o$,$ and main.o$)$

A scroll target that will combine input.o$,$ display.o$,$ and main.o into an executable called "scroll".

An all target that will depend on "scroll".

A clean target that will remove the executable scroll and all $.$o files

A run target that will run the program, compiling it first if necessary $($so it should depend on scroll$).$

Any extra targets you find helpful. For example, you may wish to include some rules for handling git tasks. Consider the benefits of having a target called commit which will commit and push the repository!