ball_absolute.v

/*
A bouncing ball using absolute coordinates.
*/
//inspired on https://8bitworkshop.com/v3.10.0/?platform=verilog&file=ball_absolute.v

module frame_display(pix_vblank, pix_y, pix_x, pix_r, pix_g, pix_b, sys_clk, sys_rst);
  input sys_clk;
  input sys_rst;
  input pix_vblank;
  input [9:0] pix_x;
  input [9:0] pix_y;
  output [7:0] pix_r, pix_g, pix_b;
  
  reg [9:0] ball_hpos;	// ball current X position
  reg [9:0] ball_vpos;	// ball current Y position
  
  //FIXME: support for sign extensions in move
  reg signed [9:0] ball_horiz_move = 1;	// ball current X velocity
  reg signed [9:0] ball_vert_move = 1;		// ball current Y velocity
  
  localparam ball_horiz_initial = 640/2;	// ball initial X position
  localparam ball_vert_initial = 480/2;	// ball initial Y position
  
  localparam BALL_SIZE = 8;		// ball size (in pixels)

  
  // update horizontal timer
  always @(posedge pix_vblank or posedge sys_rst)
  begin
    if (sys_rst) begin
      // sys_rst ball position to center
      ball_vpos <= ball_vert_initial;
      ball_hpos <= ball_horiz_initial;
    end else begin
      // add velocity vector to ball position
      ball_hpos <= ball_hpos + ball_horiz_move;
      ball_vpos <= ball_vpos + ball_vert_move;
    end
  end

  // vertical bounce
  always @(posedge ball_vert_collide)
  begin
    ball_vert_move <= -ball_vert_move;
  end

  // horizontal bounce
  always @(posedge ball_horiz_collide)
  begin
    ball_horiz_move <= -ball_horiz_move;
  end
  
  // offset of ball position from video beam
  wire [9:0] ball_hdiff = pix_x - ball_hpos;
  wire [9:0] ball_vdiff = pix_y - ball_vpos;

  // ball graphics output
  wire ball_hgfx = ball_hdiff < BALL_SIZE;
  wire ball_vgfx = ball_vdiff < BALL_SIZE;
  wire ball_gfx = ball_hgfx && ball_vgfx;

  // collide with vertical and horizontal boundaries
  // these are set when the ball touches a border
  wire ball_vert_collide = ball_vpos >= 480 - BALL_SIZE;
  wire ball_horiz_collide = ball_hpos >= 640 - BALL_SIZE;

  // combine signals to RGB output
  wire grid_gfx = (!(pix_x&28)) && (!(pix_y&28));
  wire r = ball_hgfx | ball_gfx;
  wire g = grid_gfx | ball_gfx;
  wire b = ball_vgfx | ball_gfx;

  assign pix_r = r << 7;
  assign pix_g = g << 7;
  assign pix_b = b << 7;

endmodule

dut.cc

MODULE frame_display
(  uint1 const & pix_vblank //1
  ,uint10 const & pix_y //2
  ,uint10 const & pix_x //3
  ,uint8 & pix_r //4
  ,uint8 & pix_g //5
  ,uint8 & pix_b //6
  ,uint1 const & sys_clk //7
  ,uint1 const & sys_rst //8
)
{
  uint10 var_0_ball_horiz_move_9_0_;
  uint10 var_0_ball_hpos_9_0_;
  uint10 var_0_ball_vert_move_9_0_;
  uint10 var_0_ball_vpos_9_0_;
  uint10 var_1_ball_horiz_move_9_0_;
  uint10 var_1_ball_vert_move_9_0_;
  uint10 var_add48_2_Y;
  uint10 var_add49_3_Y;
  uint32 var_and80_15_Y;
  uint32 var_and80_17_Y;
  uint1 var_ge76_13_Y;
  uint1 var_ge77_14_Y;
  uint1 var_logic_and72_12_Y;
  uint1 var_logic_and80_19_Y;
  uint1 var_logic_not80_16_Y;
  uint1 var_logic_not80_18_Y;
  uint1 var_lt70_10_Y;
  uint1 var_lt71_11_Y;
  int10 var_neg56_5_Y;
  int10 var_neg62_7_Y;
  uint1 var_or81_20_Y;
  uint1 var_or82_21_Y;
  uint1 var_or83_22_Y;
  uint8 var_shl85_23_Y;
  uint8 var_shl86_24_Y;
  uint8 var_shl87_25_Y;
  uint10 var_sub66_8_Y;
  uint10 var_sub67_9_Y;
  uint1 b;
  uint1 ball_gfx;
  uint10 ball_hdiff;
  uint1 ball_hgfx;
  uint1 ball_horiz_collide;
  int10 ball_horiz_move;
  uint10 ball_hpos;
  uint10 ball_vdiff;
  uint1 ball_vert_collide;
  int10 ball_vert_move;
  uint1 ball_vgfx;
  uint10 ball_vpos;
  uint1 g;
  uint1 grid_gfx;
  uint1 r;
  ball_horiz_move = 1; // rhs from root action
  ball_vert_move = 1; // rhs from root action
//-------LOOP-----------
while(always())
{
  ball_hdiff = var_sub66_8_Y;
  ball_vdiff = var_sub67_9_Y;
  ball_hgfx = var_lt70_10_Y;
  ball_vgfx = var_lt71_11_Y;
  ball_gfx = var_logic_and72_12_Y;
  ball_vert_collide = var_ge76_13_Y;
  ball_horiz_collide = var_ge77_14_Y;
  grid_gfx = var_logic_and80_19_Y;
  r = var_or81_20_Y;
  g = var_or82_21_Y;
  b = var_or83_22_Y;
  pix_r = var_shl85_23_Y;
  pix_g = var_shl86_24_Y;
  pix_b = var_shl87_25_Y;

  var_add48_2_Y = ball_hpos + ball_horiz_move;
  var_add49_3_Y = ball_vpos + ball_vert_move;
  var_and80_15_Y = pix_x & 28;
  var_and80_17_Y = pix_y & 28;
  var_ge76_13_Y = ball_vpos >= 472;
  ball_vert_collide = var_ge76_13_Y; //reconnection
  var_ge77_14_Y = ball_hpos >= 632;
  ball_horiz_collide = var_ge77_14_Y; //reconnection
  var_logic_and72_12_Y = ball_hgfx && ball_vgfx;
  ball_gfx = var_logic_and72_12_Y; //reconnection
  var_logic_and80_19_Y = var_logic_not80_16_Y && var_logic_not80_18_Y;
  grid_gfx = var_logic_and80_19_Y; //reconnection
  var_logic_not80_16_Y = !var_and80_15_Y;
  var_logic_not80_18_Y = !var_and80_17_Y;
  var_lt70_10_Y = ball_hdiff < 8;
  ball_hgfx = var_lt70_10_Y; //reconnection
  var_lt71_11_Y = ball_vdiff < 8;
  ball_vgfx = var_lt71_11_Y; //reconnection
  var_neg56_5_Y = -ball_vert_move;
  var_neg62_7_Y = -ball_horiz_move;
  var_or81_20_Y = ball_hgfx | ball_gfx;
  r = var_or81_20_Y; //reconnection
  var_or82_21_Y = grid_gfx | ball_gfx;
  g = var_or82_21_Y; //reconnection
  var_or83_22_Y = ball_vgfx | ball_gfx;
  b = var_or83_22_Y; //reconnection
  var_shl85_23_Y = r << 7;
  pix_r = var_shl85_23_Y; //reconnection
  var_shl86_24_Y = g << 7;
  pix_g = var_shl86_24_Y; //reconnection
  var_shl87_25_Y = b << 7;
  pix_b = var_shl87_25_Y; //reconnection
  var_sub66_8_Y = pix_x - ball_hpos;
  ball_hdiff = var_sub66_8_Y; //reconnection
  var_sub67_9_Y = pix_y - ball_vpos;
  ball_vdiff = var_sub67_9_Y; //reconnection

  var_1_ball_horiz_move_9_0_ = 1;
  var_1_ball_vert_move_9_0_ = 1;
  var_0_ball_hpos_9_0_ = ball_hpos;
  var_0_ball_vpos_9_0_ = ball_vpos;
  if(sys_rst)
  {
    var_0_ball_vpos_9_0_ = 240;
    var_0_ball_hpos_9_0_ = 320;
  }
  else
  {
    var_0_ball_hpos_9_0_ = var_add48_2_Y;
    var_0_ball_vpos_9_0_ = var_add49_3_Y;
  }
  var_0_ball_vert_move_9_0_ = var_neg56_5_Y;
  var_0_ball_horiz_move_9_0_ = var_neg62_7_Y;

  if(posedge(pix_vblank))
    ball_hpos = var_0_ball_hpos_9_0_;
  if(posedge(pix_vblank))
    ball_vpos = var_0_ball_vpos_9_0_;
  if(posedge(sys_rst))
    ball_hpos = var_0_ball_hpos_9_0_;
  if(posedge(sys_rst))
    ball_vpos = var_0_ball_vpos_9_0_;
  if(posedge(ball_vert_collide))
    ball_vert_move = var_0_ball_vert_move_9_0_;
  if(posedge(ball_horiz_collide))
    ball_horiz_move = var_0_ball_horiz_move_9_0_;
}
}