CS2260 Media Device Architectures Timing Code, Organizing C Files, First Project

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CS2260 Media Device ArchitecturesTiming Code,
Organizing C Files, First Project
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Revisit assignment 2, 4b

• This is the use pageflipping to move a circle in
  mode 5 assignment
• Need to erase the circle in each page
• One way is to keep track of where the circle is
  drawn in each page and redraw the circle in the
  background color
• Another way is to clear the whole page by
  redrawing every pixel in the background color
• A number of you did this you may have noticed
  that the circle moves slowly
• Lets time how long it takes to clear the screen

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Timing ClearScreen()

• REG_TM0D 0
• REG_TM1D 0
• REG_TM0CNT TIMER_FREQUENCY_SYSTEM
  TIMER_ENABLE
• REG_TM1CNT TIMER_OVERFLOW TIMER_ENABLE
• ClearScreen()
• REG_TM0CNT TIMER_ENABLE
• REG_TM1CNT TIMER_ENABLE
• Now how do we print out the timer value?

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Detour making a general bitmap Print() routine

• Wed like to be able to easily print in bitmap
  mode 3, 4 or 5
• The book gives us code for drawing in mode 3
• One approach manually modify the code and copy
  and paste it into your program
• Better Build a general Print() library that you
  can reuse in any bitmap mode program
• Need to make the routines work in any bitmap mode
• Need to define a .h file that provides the
  defines and function prototypes of your library
• Need to tell Ham to use the library

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Details of modifying Print()

• Work an example in Ham

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DMA

• Direct memory access (DMA) uses a special piece
  of hardware, the DMA controller, to move data
  around
• The CPU is paused during DMA access
• DMA cant move data faster than the clock rate
• At last two clock cycles per word (16 bit) moved,
  usually more because of memory wait states

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Long story short

• Dont clear the whole screen unless you really
  have to
• For simple things, like moving a circle or
  playing Pong, it is easy to figure out what needs
  to be erased, so just erase that
• Speaking of Pong

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First project

• Build a simple racquet ball game
• Bounce a ball against a wall
• Slowly speed up the ball the score is how many
  seconds you keep the ball bouncing

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Issues to think about

• Which graphics mode should we use?
• We want to avoid artifacts
• Dont need a lot of color
• Mode 4 high resolution, have a second page for
  artifact-free drawing, enough color (256)
• We dont have a paddle controller how can we
  make moving a paddle more interesting with button
  controls?
• Dual speed press A to move faster
• What do we need to draw? How should we draw it?

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More issues

• How should we count seconds as they go by?
• How should the ball bounce?
• If it hits a stationary paddle or wall
• If it hits a moving paddle
• Angle of incidence angle of reflection
• Perhaps add to the angle of reflection as you
  move out from the center of paddle
• Perhaps add to the angle of reflection in the
  direction of movement if you hit a moving paddle
• How should we indicate increasing difficulty?