CS2261 LAB 05: Solution

Structs, Object
Pooling, and DMA
Provided Files
● main.c
● gba.c, gba.h
● game.c, game.h
● font.c, font.h
● sound.h
Files to Edit/Add from Lab00
● Makefile
● .vscode
○ tasks.json
● main.c
● gba.c
● game.c, game.h
Instructions
In this lab you will be completing several different TODOs, which will complete a simple Brick Breaker game. Each TODO represents a component of the game, and is broken down into sub-TODOs. Your code will likely not compile until you complete an entire TODO block, at which point the game should compile with the new component added and working.
After you download and unzip the files, add your Makefile and your tasks.json, and then compile and run it. At this point, you should see the start screen. Complete the TODOs in order, paying close attention to the instructions.

TODO 1: Score
We have provided drawChar and drawString for you. We want to be able to see our current progress to victory during the game state.
TODO 1.0
● In goToGame(), draw "score:" at (180, 1) using the color HOTPINK.
TODO 1.1
● In game(), use sprintf() to save the current score (score) in the text form to a character array.
○ The char array has already been created for you, called buffer. sprintf is a function in sdio.h, which we have #include'd for you. It returns null, and works like this:
■ sprintf(ptrName, formatterString, variables, …)
■ This is exactly like printf, but with an extra argument at the beginning (the ptrName to save to).
TODO 1.2
● We want to erase the previous score before we draw the new one! Draw an OFFWHITE rectangle at (220, 1) that is the size of a character.
○ Hint: Look back at font.c – how wide and how tall is each character?
● Then, draw the score at this location (using drawString with buffer as the character array parameter input) in PORTAGE.
TODO 1.3
● Inside of main.c, update the start() function to increment the seed variable (rSeed) every frame.
● Then, when the player presses START to transition to the GAME state, use srand() to seed the random number generator using rSeed.
Build and run. You should be able to travel to the game state and see the current score. Right now, it will be 0. In the next TODO, we will add blocks that can be broken to increase the score.
Note: Why did we draw "score:" in goToGame(), but the actual number in game()? That's because the "score:" text does not change, so we only need to draw it once. The actual score, however, can change at any time, so we have to account for that possibility every frame.
TODO 2: Blocks
Now we will add the bricks to be broken! This will take place in game.h and game.c.
TODO 2.0
● In game.h, create the struct for the blocks, typedef-ed BLOCK. BLOCK should have the following members: x, y, oldx, oldy,xVelocity, width, height, color, active, and erased. All of the BLOCK members should be of type int except color, which should be an unsigned short.
TODO 2.1
● In game.c, uncomment initBlocks().
● Inside initBlocks(), change colorPicker to choose a random number between 0 and 4 (inclusive) using rand().
TODO 2.2
● Also in game.c, uncomment drawBlocks().
TODO 2.3
● Uncomment the updateBlocks() function. This takes in a pointer to a block. If the block is inactive, the function does nothing. If it is active, it performs the collision checks we wrote for you. Inside of the main collision check, set the block to inactive and not erased (active = 0, erased = 0), and increment score by 1.
TODO 2.4
● In updateGame(), call updateBlock() for each of your blocks.
○ Hint: the number of blocks is a macro named BLOCKCOUNT and the blocks are stored in an array named blocks.
TODO 2.5
● Complete newBlock(). This should iterate through the blocks to find the first inactive block in the pool and initialize it. When you are finished initializing, break out of the loop. Initialize the block like so:
○ active: 1
○ erased: 0
Compile and run. When you enter the game state, you should see layers of blocks of different colors. Each time you restart the game, you should see them being different colors (since we randomized it and seeded our random number generator). Note: When you hit a block, sometimes it will seem to not disappear. This is because we are calling newBlock to immediately set a block to be active again which is sometimes the block we just destroyed. This is intended, don’t worry!
TODO 3: DMA
For our game to be fast, we need to use DMA. The simplest way to do this is to write a function that sets up the registers of the specified channel.
TODO 3.0
● In gba.c, complete the DMANow function.
○ This function should set up all the registers of the given DMA channel and turn it on for us. This allows us to use DMA whenever we need it with a single line, without having to set all the registers line-by-line in every location we want to use it. There are additional comments in the DMANow function that will help you write it.
TODO 3.1
● Rewrite the fillScreen function to use DMA, using your new DMANow function.
○ Hint: If you are copying one thing (one single source) to every pixel in the videoBuffer, what do you need to tell the DMA control to do (or not do) to the source? Look at gba.h for helper macros!
○ Hint: Make sure the src and dst parameters are addresses to the locations you are copying from and to.
TODO 3.2
● Rewrite the drawRect function to use DMA, using your new DMANow function.
○ Hint: You must use one loop here because, unlike fillScreen, the area you are copying to (dest) is not contiguous. Each row of the rectangle is, though. Use DMA to draw one row at a time.
○ Hint: Make sure the src and dst parameters are addresses to the locations you are copying from and to.
Build and run. The game should look the same, but a lot snappier during transitions. If not, fix it before moving forward.
TODO 4: Analog/DMG Sound
Finally, let's add a fun little beep whenever there is a collision between a block and the ball to make our game slightly more interesting.
TODO 4.0
● Inside initialize() in main.c, enable sounds in the sound on/off register (REG_SOUNDCNT_X).
○ Hint: We might have made a useful macro that sets bit 7 for you! Check out sound.h to see all the macros for sound.
TODO 4.1
● In updateBlocks() in game.c, use sound channel 2 to play a sound with the following characteristics:
○ The volume of the envelope (DMG_ENV_VOL) should be 4. ○ The step time (DMG_STEP_TIME) should be 2/64.
■ Hint: Whatever value you put in those bits in memory is automatically divided by 64!
○ The note played should be G6.
■ Hint: Use the NOTES enum!
○ Set the reset bit (SND_RESET) so that the sound is reset to initial volume settings.
● Remember that there are two main registers we need to set when we use channel 2, REG_SND2CNT and REG_SND2FREQ. Look over the slides (or TONC, or GBATek) to see which register controls what for the above settings!
Build and run. Compare your lab to the provided Example.gba. If everything works identically, submit your lab.

Submission Instructions
Ensure that cleaning and building/running your project still gives the expected results. Please reference previous assignments for instructions on how to perform a "clean" command.
Zip up your entire project folder, including all source files, the Makefile, and everything produced during compilation (including the .gba file). Submit this on Canvas. Name your submission Lab05_LastnameFirstname, for example:
"Lab05_BandersonBarson.zip"
It is your responsibility to ensure that all the appropriate files have been submitted, and that your submitted zip can be opened and everything cleans, builds, and runs as expected.