George Mason UniversityECE 448 – FPGA and ASIC Design with VHDL

VGA DisplayPart 3

Animation

ECE 448Lecture 11

2ECE 448 – FPGA and ASIC Design with VHDL

Required Reading

• P. Chu, FPGA Prototyping by VHDL Examples Chapter 12, VGA Controller I: Graphic

•Source Codes of Examples http://academic.csuohio.edu/chu_p/rtl/fpga_vhdl.html

•Nexys 3 Board Reference Manual VGA Port, pages 15-17

3ECE 448 – FPGA and ASIC Design with VHDL

PONG

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PONG

ECE 448 – FPGA and ASIC Design with VHDL

• Commonly regarded as the first "commercially successful" video game• Released by Atari in 1972• Created by Allan Alcorn as a training exercise assigned to him by Atari co-founder Nolan Bushnell• The first prototype developed completely in hardware using TTL devices• Originally used as an arcade video game• Home version released during the 1975 Christmas

season

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PONG

ECE 448 – FPGA and ASIC Design with VHDL

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PONG – Interesting Videos

ECE 448 – FPGA and ASIC Design with VHDL

Pong Gamehttp://www.ponggame.org

First documented Video Ping-Pong game – 1969https://www.youtube.com/watch?v=XNRx5hc4gYc

Classic Game Room HD - PONG for Nintendo DS / GBAhttps://www.youtube.com/watch?v=TrezFjGF-Kg

7ECE 448 – FPGA and ASIC Design with VHDL

Animation

8

Animation Basics

ECE 448 – FPGA and ASIC Design with VHDL

• Animation is achieved by an object changing its location gradually in each frame• We use signals, instead of constants, to determine boundaries of an object• VGA monitor is refreshed 60 times per second• The boundary signals need to be updated at this rate• We create a 60 Hz enable tick, refr_tick, which is asserted for 1 pixel period every 1/60th of a second

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Moving the Bar (Paddle)

ECE 448 – FPGA and ASIC Design with VHDL

600 ≤ x ≤ 603bar_y_t ≤ y ≤ bar_y_b

bar_y_t = bar_y_regbar_y_b=bar_y_t+BAR_Y

_SIZE-1

BAR_V is a velocityof the bar (#pixels/frame)

10ECE 448 – FPGA and ASIC Design with VHDL

-- bar left, right boundary constant BAR_X_L: integer:=600; constant BAR_X_R: integer:=603;

-- bar top, bottom boundary signal bar_y_t, bar_y_b: unsigned(9 downto 0); constant BAR_Y_SIZE: integer:=72;

-- reg to track top boundary (x position is fixed) signal bar_y_reg, bar_y_next: unsigned(9 downto 0);

-- bar moving velocity when the button is pressed constant BAR_V: integer:=4;

Moving the Bar in VHDL (1)

11ECE 448 – FPGA and ASIC Design with VHDL

-- boundary bar_y_t <= bar_y_reg; bar_y_b <= bar_y_t + BAR_Y_SIZE - 1;

-- pixel within bar bar_on <= '1' when (BAR_X_L<=pix_x) and (pix_x<=BAR_X_R) and (bar_y_t<=pix_y) and (pix_y<=bar_y_b) else '0';

-- bar rgb output bar_rgb <= "010"; --green

Moving the Bar in VHDL (2)

12ECE 448 – FPGA and ASIC Design with VHDL

-- new bar y-positionprocess(bar_y_reg, bar_y_b, bar_y_t, refr_tick, btn)begin bar_y_next <= bar_y_reg; -- no move if refr_tick='1' then if btn(1)='1' and bar_y_b <= (MAX_Y-1-BAR_V) then bar_y_next <= bar_y_reg + BAR_V; -- move down elsif btn(0)='1' and bar_y_t >= BAR_V then bar_y_next <= bar_y_reg - BAR_V; -- move up end if; end if;end process;

Moving the Bar in VHDL (3)

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Circuit calculating bar_y_next

ECE 448 – FPGA and ASIC Design with VHDL

14ECE 448 – FPGA and ASIC Design with VHDL

process (clk, reset)begin if reset='1' then bar_y_reg <= (others=>'0'); elsif (clk'event and clk='1') then bar_y_reg <= bar_y_next; end if;end process;

Moving the Bar in VHDL (4)

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bar_y_reg, bar_y_t, and bar_y_b

ECE 448 – FPGA and ASIC Design with VHDL

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Moving the Ball

ECE 448 – FPGA and ASIC Design with VHDL

ball_x_l ≤ x ≤ ball_x_rball_y_t ≤ y ≤ ball_y_b

ball_x_l = ball_x_regball_x_r=ball_x_l+BALL_

SIZE-1

ball_y_t = ball_y_regball_y_b=ball_y_t+BALL_

SIZE-1

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Ball Velocity

ECE 448 – FPGA and ASIC Design with VHDL

• The ball may change direction by hitting the wall, the paddle, or the bottom or top of the screen• We decompose velocity into an x-component and a y-component• Each component can have either a positive value BALL_V_P or a negative value BALL_V_N• The current value of each component is kept in x_delta_reg and y_delta_reg

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Velocity Components of the Ball

ECE 448 – FPGA and ASIC Design with VHDL

x_delta_reg = BALL_V_Py_delta_reg = BALL_V_P

x

y

x_delta_reg = BALL_V_Py_delta_reg = BALL_V_N

x_delta_reg = BALL_V_Ny_delta_reg = BALL_V_N

x_delta_reg = BALL_V_Ny_delta_reg = BALL_V_P

19ECE 448 – FPGA and ASIC Design with VHDL

constant BALL_SIZE: integer:=8; -- 8 -- ball boundaries signal ball_x_l, ball_x_r: unsigned(9 downto 0); signal ball_y_t, ball_y_b: unsigned(9 downto 0); -- reg to track left, top boundary signal ball_x_reg, ball_x_next: unsigned(9 downto 0); signal ball_y_reg, ball_y_next: unsigned(9 downto 0); -- reg to track ball speed signal x_delta_reg, x_delta_next: unsigned(9 downto 0); signal y_delta_reg, y_delta_next: unsigned(9 downto 0); -- ball velocity can be pos or neg constant BALL_V_P: unsigned(9 downto 0) := to_unsigned(2,10); constant BALL_V_N: unsigned(9 downto 0) := unsigned(to_signed(-2,10));

Moving the Ball in VHDL (1)

20ECE 448 – FPGA and ASIC Design with VHDL

type rom_type is array (0 to 7) of std_logic_vector(0 to 7);constant BALL_ROM: rom_type := ( "00111100", -- **** "01111110", -- ****** "11111111", -- ******** "11111111", -- ******** "11111111", -- ******** "11111111", -- ******** "01111110", -- ****** "00111100" -- **** ); signal rom_addr, rom_col: unsigned(2 downto 0); signal rom_data: std_logic_vector(0 to 7); signal rom_bit: std_logic;

Moving the Ball in VHDL (2)

21ECE 448 – FPGA and ASIC Design with VHDL

ball_x_l <= ball_x_reg; ball_y_t <= ball_y_reg; ball_x_r <= ball_x_l + BALL_SIZE - 1; ball_y_b <= ball_y_t + BALL_SIZE - 1;

-- pixel within ball sq_ball_on <= '1' when (ball_x_l<=pix_x) and (pix_x<=ball_x_r) and (ball_y_t<=pix_y) and (pix_y<=ball_y_b) else '0';

Moving the Ball in VHDL (3)

22ECE 448 – FPGA and ASIC Design with VHDL

-- map current pixel location to ROM addr/col rom_addr <= pix_y(2 downto 0) - ball_y_t(2 downto 0); rom_col <= pix_x(2 downto 0) - ball_x_l(2 downto 0); rom_data <= BALL_ROM(to_integer(rom_addr)); rom_bit <= rom_data(to_integer(rom_col));

-- pixel within ball rd_ball_on <= '1' when (sq_ball_on='1') and (rom_bit='1') else '0';

-- ball rgb output ball_rgb <= "100"; -- red

Moving the Ball in VHDL (4)

23ECE 448 – FPGA and ASIC Design with VHDL

-- new ball position ball_x_next <= ball_x_reg + x_delta_reg when refr_tick='1' else ball_x_reg ; ball_y_next <= ball_y_reg + y_delta_reg when refr_tick='1' else ball_y_reg ;

Moving the Ball in VHDL (5)

24ECE 448 – FPGA and ASIC Design with VHDL

process(x_delta_reg, y_delta_reg, ball_x_l, ball_x_r, ball_y_t, ball_y_b, bar_y_t, bar_y_b) begin x_delta_next <= x_delta_reg; y_delta_next <= y_delta_reg; if ball_y_t < 1 then -- reach top y_delta_next <= BALL_V_P; elsif ball_y_b >= (MAX_Y-1) then -- reach bottom y_delta_next <= BALL_V_N; elsif ball_x_l <= WALL_X_R then -- reach wall x_delta_next <= BALL_V_P; -- bounce back elsif (BAR_X_L<=ball_x_r) and (ball_x_r<=BAR_X_R) then -- reach x of right bar if (bar_y_t<=ball_y_b) and (ball_y_t<=bar_y_b) then x_delta_next <= BALL_V_N; --hit, bounce back end if; end if; end process;

Moving the Ball in VHDL (6)

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Bouncing

ECE 448 – FPGA and ASIC Design with VHDL

y_delta_next <= BALL_V_P

y_delta_next <= BALL_V_N

x_delta_next <= BALL_V_P x_delta_next <= BALL_V_N

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Circuit calculating y_delta_next

ECE 448 – FPGA and ASIC Design with VHDL

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Circuit calculating x_delta_next

ECE 448 – FPGA and ASIC Design with VHDL

28ECE 448 – FPGA and ASIC Design with VHDL

process (clk, reset) begin if reset='1' then ball_x_reg <= (others=>'0'); ball_y_reg <= (others=>'0'); x_delta_reg <= BALL_V_P; y_delta_reg <= BALL_V_P; elsif (clk'event and clk='1') then ball_x_reg <= ball_x_next; ball_y_reg <= ball_y_next; x_delta_reg <= x_delta_next; y_delta_reg <= y_delta_next; end if; end process;

Moving the Ball in VHDL (7)

29ECE 448 – FPGA and ASIC Design with VHDL

pix_x <= unsigned(pixel_x); pix_y <= unsigned(pixel_y);

-- refr_tick: 1-clock tick asserted at start of v-sync -- i.e., when the screen is refreshed (60 Hz)refr_tick <= '1' when (pix_y=481) and (pix_x=0) else '0';

Generating ref_tick in VHDL

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Vertical Synchronization

ECE 448 – FPGA and ASIC Design with VHDL