Homework 10 GBA Solution

Overview



The goal of this assignment is to make a C program that will run on the GBA emulator. Your program should include everything in the requirements and be written neatly and e ciently. Your main.c should be something di erent from lecture code, since in this homework you will be creating your own program. However, you will keep the core setup with videoBuffer, MODE 3, waitForVBlank, etc.




Prototypes, #define’s, and extern declarations should be put into a myLib.h. You may use other .c and .h les to organize your logic if you wish. Make sure you include them in both your submission and Makefile.




Additionally, we want to make one point very clear: Please do not rehash lecture code in your program. This means you are not allowed to slightly modify lecture code and \call it a day." If we open your program and discover several boxes ying in random directions, that will be a very bad sign. Consequently, you will not receive a very pleasant grade.




1.1 Resources




To tackle this homework, we’ve provided:




A myLib.h le containing all of the necessary GBA declarations such as DMA, videoBuffer, etc. A Makefile you can use to compile and run your program by typing make vba




Feel free to use code from these class resources, as you need to, but not from your friends or random, sketchy internet sites.




1.2 Warnings




Do not use float’s or double’s in your code. Doing so will slow your code down greatly. The ARM7 processor the GBA uses does not have a Floating Point Unit which means oating point operations are slow and done in software, not hardware. Anywhere you use float’s, gcc has to insert assembly code to convert integers to that format. If you do need such things then you should look into xed point math.




Only call waitForVBlank once per iteration of your main loop




Keep your code e cient. If an O(1) solution exists to an algorithm and you are using an O(n2) algorithm then that’s bad (for larger values of n)! Contrary to this, only worry about e ciency if your program is showing signs of tearing!




If you use more advanced GBA features like sprites or sound, making them work is your responsibility; we (the TAs) don’t necessarily know how they work, so we can’t help you.









Requirements



Should be in Mode 3:




{ You may use other modes (e.g. Mode 0, Mode 4), but do so at your own risk. It will be di cult to get TA help for modes other than Mode 3.




You must also implement drawImage3 with direct memory access (DMA). The prototype and expla-nation are given later in the assignment. If DMA has not been covered in lecture yet, you can rst implement this function with setPixel, and then re-implement it with DMA once it’s been covered in lecture.




You must use 3 distinct images in your program, all drawn with DMA:




{ Two full screened images sized 240 160. One of these images should be the rst screen displayed when rst running your program.




{ A third image which will be used during the course of your program. The width of this image may not be 240 and the height of this image may not be 160.




{ Note: All images should be included in your submission.




You must be able to reset the program to the title screen AT ANY TIME using the SELECT key.




You must create a header (myLib.h), and move any #define’s, function prototypes, and typedef’s to this le from your code, along with your extern videoBuffer statement if you wish to use videoBuffer in other les. Remember that function and variable de nitions should not go in header les, just prototypes and extern variable declarations.




You must use at least one struct.




Button input should visibly and clearly a ect the ow of the program




You must have two-dimensional movement of at least one entity. One entity moving up and down and another moving left and right alone does not count.




You should implement some form of object collision. For programs where application of this rule is more of a gray area (like Minesweeper), core functionality will take the place of this criteria, such as the numbers for Minesweeper tiles calculated correctly, accurate control, etc.




You must implement waitForVBlank and the SCANLINECOUNTER declaration.




Use text to show progression in your program. Use the example les from lecture, and you can nd more information in Tonc: http://www.coranac.com/tonc/text/text.htm




There must be no tearing in your program. Make your code as e cient as possible!




Include a README.txt le with your submission which brie y explains the program and controls.




Do not include .c les into other les. Only .h les should be included and .h les should contain no functional code!







Deliverables



Please archive your source code les as a .zip or a .tar and upload to Canvas under the \Homework 10" assignment.




This includes all .c and .h les needed for your program to compile. Do not submit any compiled les. You can use make clean to remove any compiled les.




Download and test your submission to make sure you submitted the right les.



What to Make?



You may either: (1) create your own program, the way you wish it to be, as long as it covers the requirements, or (2) you can make programs that have been made before with your own code.




Your assignment must be entirely yours and not based on anyone else’s code. As a reminder, this means you may not base your program on the code posted from lecture. Programs slightly modi ed from lecture code will be subject to heavy penalties.




Here are some previous programs you can either create or use as inspiration:




Interactive Storybook:




Recreate a story from a movie or a book using the GBA




Use text to narrate what is currently happening in the scene



Use the controls to advance to the next scene or control a character within the scene Smooth movement (for any moving characters or objects)




Start o with a full screen title image and end with a full screen credits image




Galaga:




Use text to show lives




Game ends when all lives are lost, and level ends when all aliens are gone




Di erent types of aliens: there should be one type of alien that rushes towards the ship and attacks it Smooth movement (aliens and player)




The World’s Hardest Game:




Smooth motion for enemies and player (no jumping around) Constriction to the boundaries of the level




Enemies moving at di erent speeds and in di erent directions Sensible, repeating patterns of enemy motion




Enemies and the Player represented by Structs




Flyswatter:




Images of yellow jackets or ies moving smoothly across the screen Player controlled yswatter or net to catch the ies




Score counter to keep track of how many ies have been swatted Fullscreen image for title screen and game background




Enemies and the Player represented by Structs




Note: Do not make Pong! Everyone asks if they can make Pong, and it’s simply a boring, low-e ort product.






GBA Coding Guidelines



5.1 Installing Dependencies




To install dependencies, run:




$ sudo apt update




$ sudo apt install gcc-arm-none-eabi cs2110-vbam-sdl cs2110-gba-linker-script nin10kit




Note that this requires Brandon \The Machine" Whitehead’s CS 2110 PPA, which you should’ve added earlier in the class for complx. If you need to re-add this, run the following and then run the two commands above again:




$ sudo add-apt-repository ppa:tricksterguy87/ppa-gt-cs2110




5.2 Building and Running your Code




To build your code and run the GBA emulator, run:




$ make vba




5.3 Images




As a requirement, you must use at least three images in your program and draw them all using drawImage3. To use images on the GBA, you rst need to convert them into the suitable format. We recommend using a tool called nin10kit, which you installed with the command above.




You can read about nin10kit in the nin10kit documentation (there are pictures!):




https://github.com/TricksterGuy/nin10kit/raw/master/readme.pdf




nin10kit reads in, converts, and exports image les into C arrays in .c and .h les ready to be copied to the GBA video bu er by your implementation of drawImage3! It also supports resizing images before they are exported.




You want to use Mode 3, since this assignment requires it, so in order to convert a picture of smelly, festering garbage into GBA pixel format in garbage.c and garbage.h, resizing it to 50 horizontal by 37 vertical pixels, you would run nin10kit with the following command:




$ nin10kit --mode=3 --resize=50x37 garbage garbage.png




This creates a garbage.h le containing:




extern const unsigned short garbage[1850];




#define GARBAGE_SIZE 3700




#define GARBAGE_LENGTH 1850




#define GARBAGE_WIDTH 50




#define GARBAGE_HEIGHT 37




You can use this in your program by inserting #include "garbage.h".




The garbage.c generated, which you should add to the Makefile under OFILES as garbage.o if you plan to use it, contains all of the pixel data in a huge array:



const unsigned short garbage[1850] =



{




0x7fff,0x7fff,0x7fff,0x7fff,0x7fff, // ...




0x7fff,0x7fff,0x7fff,0x7fff,0x7fff, // ...




...



0x7fff,0x7fff,0x7fff,0x7fff,0x7fff, // ...




0x7fff,0x7fff,0x7fff,0x7fff,0x7fff, // ...




};




We’ve included garbage.png, garbage.c, and garbage.h in the homework .zip so you can check them out yourself. To draw the garbage in your own game, you can pass the array, width and height to your drawImage3 accordingly: drawImage3(10, 20, GARBAGE WIDTH, GARBAGE HEIGHT, garbage) (to draw at row 10 and column 20). The next section will cover drawImage3 in more detail.







5.4 DMA / drawImage3




In your program, you must use DMA to code drawImage3.




Drawing to the GBA screen follows the same guidelines as the graphics functions you implemented for Homework 09. The GBA screen is represented with a short pointer declared as videoBuffer in the myLib.h le. The pointer represents the rst pixel in a 240 by 160 screen that has been attened into a one-dimensional array. Each pixel is a short and has a red, green, and blue portion just like the pixels in Homework 09. There is a little modi cation (Hint: Include the graphics and geometry header les and use videoBuffer as the screen bu er), but you should be able to use the same code you implemented in Homework 09 to draw to the GBA screen.




DMA stands for Direct Memory Access and may be used to make your rendering code run much faster. If you want to read up on DMA before it is covered in lecture, you may read these pages from Tonc: http://www.coranac.com/tonc/text/dma.htm (Up until 14.3.2).




If you want to wait, you can choose to implement drawImage3 without DMA and then, when you learn DMA, rewrite it. Your nal answer for drawImage3 must use DMA!




You must not use DMA for one pixel copies. Doing this defeats the purpose of DMA and is slower than using setPixel! Solutions which do this will receive no credit for that function.




The prototype and parameters for drawImage3 are as follows:




/* drawimage3




A function that will draw an arbitrary sized image



onto the screen (with DMA).



@param r row to draw the image



@param c column to draw the image



@param width width of the image



@param height height of the image



@param image Pointer to the first element of the image.



*/




void drawImage3 (int r, int c, int width, int height, const u16* image)




{




// @todo implement :)




}




Note: If your implementation of this function does not use all parameters passed in then you are not implementing the function correctly. Understand that DMA acts as a for loop, but it is done in hardware. You should draw each row of the image, and allow DMA to handle drawing each row of the image.


5.5 GBA Controls




Here are inputs from the GameBoy based on the keyboard for the default emulator vbam:




Gameboy
Keyboard




Start
Enter




Select
Backspace




A
Z




B
X




L
A




R
S







The directional arrows are mapped to the same directional arrows on the keyboard.




5.6 C Coding Conventions




Do not jam all your code into one function (i.e. the main function).




Split your code into multiple les. For example, you can have logic in your main le and library functions in myLib.c with declarations in myLib.h.




Do not include .c les in other les. Only .h les should be included. .h les should contain no functional code.




Comment your code, and comment what each function does. The quality of your comments will be factored into your grade!







Rules and Regulations



6.1 General Rules




Starting with the assembly homeworks, Any code you write (if any) must be clearly commented and the comments must be meaningful. You should comment your code in terms of the algorithm you are implementing we all know what the line of code does.



Although you may ask TAs for clari cation, you are ultimately responsible for what you submit. This means that (in the case of demos) you should come prepared to explain to the TA how any piece of code you submitted works, even if you copied it from the book or read about it on the internet.



Please read the assignment in its entirety before asking questions.



Please start assignments early, and ask for help early. Do not email us the night the assignment is due with questions.



If you nd any problems with the assignment it would be greatly appreciated if you reported them to the author (which can be found at the top of the assignment). Announcements will be posted if the assignment changes.



6.2 Submission Conventions




All les you submit for assignments in this course should have your name at the top of the le as a comment for any source code le, and somewhere in the le, near the top, for other les unless otherwise noted.





When preparing your submission you may either submit the les individually to Canvas or you may submit an archive (zip or tar.gz only please) of the les (preferred). You can create an archive by right clicking on les and selecting the appropriate compress option on your system.



If you choose to submit an archive please don’t zip up a folder with the les, only submit an archive of the les we want (see Deliverables).



Do not submit compiled les that is .class les for Java code and .o les for C code. Only submit the les we ask for in the assignment.



Do not submit links to les. We will not grade assignments submitted this way as it is easy to change the les after the submission period ends.



6.3 Submission Guidelines




You are responsible for turning in assignments on time. This includes allowing for unforeseen circum-stances. If you have an emergency let us know IN ADVANCE of the due time supplying documenta-tion (i.e. note from the dean, doctor’s note, etc). Extensions will only be granted to those who contact us in advance of the deadline and no extensions will be made after the due date.



You are also responsible for ensuring that what you turned in is what you meant to turn in. After submitting you should be sure to download your submission into a brand new folder and test if it works. No excuses if you submit the wrong les, what you turn in is what we grade. In addition, your assignment must be turned in via Canvas. Under no circumstances whatsoever we will accept any email submission of an assignment. Note: if you were granted an extension you will still turn in the assignment over Canvas.



There is a 6-hour grace period added to all assignments. You may submit your assignment without penalty up until 11:55PM, or with 25% penalty up until 5:55AM. So what you should take from this is not to start assignments on the last day and plan to submit right at 11:54AM. You alone are responsible for submitting your homework before the grace period begins or ends; neither Canvas, nor your aky internet are to blame if you are unable to submit because you banked on your computer working up until 11:54PM. The penalty for submitting during the grace period (25%) or after (no credit) is non-negotiable.



6.4 Syllabus Excerpt on Academic Misconduct




Academic misconduct is taken very seriously in this class. Quizzes, timed labs and the nal examination are individual work.




Homework assignments are collaborative, In addition many if not all homework assignments will be evaluated via demo or code review. During this evaluation, you will be expected to be able to explain every aspect of your submission. Homework assignments will also be examined using computer programs to nd evidence of unauthorized collaboration.




What is unauthorized collaboration? Each individual programming assignment should be coded by you. You may work with others, but each student should be turning in their own version of the assignment. Submissions that are essentially identical will receive a zero and will be sent to the Dean of Students’ O ce of Academic Integrity. Submissions that are copies that have been super cially modi ed to conceal that they are copies are also considered unauthorized collaboration.




You are expressly forbidden to supply a copy of your homework to another student via elec-tronic means. This includes simply e-mailing it to them so they can look at it. If you supply an electronic copy of your homework to another student and they are charged with copying, you will also be charged. This includes storing your code on any site which would allow other parties to obtain your code such as but not limited to public repositories (Github), pastebin, etc. If you would like to use version control, use github.gatech.edu






6.5 Is collaboration allowed?



Collaboration is allowed on a high level, meaning that you may discuss design points and concepts relevant to the homework with your peers, as well as help each other debug code. What you shouldn’t be doing, however, is paired programming where you collaborate with each other on a low level. Furthermore, sending an electronic copy of your homework to another student for them to look at and gure out what is wrong with their code is not an acceptable way to help them, and it is often the case that the recipient will simply modify the code and submit it as their own.