ECE 448 Lecture 11 VGA Display Part 3 Animation George Mason University
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 Nexys 4 DDR FPGA Board Reference Manual VGA Port 2
PONG 3
PONG 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 4
PONG 5
PONG Interesting Videos Pong Game http://www.ponggame.org First documented Video Ping-Pong game 1969 https://www.youtube.com/watch?v=xnrx5hc4gyc Classic Game Room HD - PONG for Nintendo DS / GBA https://www.youtube.com/watch?v=trezfjgf-kg 6
Animation 7
Animation Basics 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 1/60 th of a second 8
Moving the Bar (Paddle) 600 x 603 bar_y_t y bar_y_b bar_y_t = bar_y_reg bar_y_b=bar_y_t +BAR_Y_SIZE-1 BAR_V is a velocity of the bar (#pixels/frame) 9
Moving the Bar in VHDL (1) -- 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; 10
Moving the Bar in VHDL (2) -- 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 11
bar_y_reg, bar_y_t, and bar_y_b 12
Moving the Bar in VHDL (4) 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; 13
Circuit calculating bar_y_next 14
Moving the Bar in VHDL (3) -- new bar y-position process(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; 15
Moving the Ball ball_x_l x ball_x_r ball_y_t y ball_y_b ball_x_l = ball_x_reg ball_x_r=ball_x_l +BALL_SIZE-1 ball_y_t = ball_y_reg ball_y_b=ball_y_t +BALL_SIZE-1 16
Ball Velocity 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 17
Velocity Components of the Ball x x_delta_reg = BALL_V_N y_delta_reg = BALL_V_N x_delta_reg = BALL_V_P y_delta_reg = BALL_V_N x_delta_reg = BALL_V_N y_delta_reg = BALL_V_P x_delta_reg = BALL_V_P y_delta_reg = BALL_V_P y 18
Moving the Ball in VHDL (1) 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)); 19
Moving the Ball in VHDL (3) 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 '0'; (ball_y_t<=pix_y) and (pix_y<=ball_y_b) else 20
Moving the Ball in VHDL (2) 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; 21
Moving the Ball in VHDL (4) -- 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 22
Moving the Ball in VHDL (5) -- 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 ; 23
Bouncing y_delta_next <= BALL_V_P x_delta_next <= BALL_V_P x_delta_next <= BALL_V_N y_delta_next <= BALL_V_N 24
Circuit calculating y_delta_next 25
Circuit calculating x_delta_next 26
Moving the Ball in VHDL (6) 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; if ball_y_t < 1 then -- reach top y_delta_next <= BALL_V_P; y_delta_next <= y_delta_reg; 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; 27
Moving the Ball in VHDL (7) 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; 28
Generating ref_tick in 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'; 29
Vertical Synchronization 30