Obst_ctl

`timescale 1ns / 1ps
//////////////////////////////////////////////////////////////////////////////////
// Company:
// Engineer:
//
// Create Date: 01.04.2019 22:36:45
// Design Name:
// Module Name: draw_rect_ctl
// Project Name:
// Target Devices:
// Tool Versions:
// Description:
//
// Dependencies:
//
// Revision:
// Revision 0.01 - File Created
// Additional Comments:
//
//////////////////////////////////////////////////////////////////////////////////


module dynamic_obst_ctl(
   input wire clk,          //100 Hz
   input wire rst,
   output reg [11:0] xpos,
   output reg [11:0] ypos
);

localparam VER_PIXELS = 600;
localparam RECT_HEIGHT = 50;
localparam v = 2;

localparam XPOS_INIT = 600;
localparam YPOS_INIT = 1;

localparam DOWN = 2'b01, UP = 2'b10, CHANGE_DIRECTION = 2'b11;

reg [11:0] xpos_nxt, ypos_nxt;
reg [15:0] t, t_nxt;
reg GO_UP;
reg [1:0] state, state_nxt;

always @(posedge clk) begin
    if (rst) begin
        xpos <= 0;
        ypos <= 0;
        t <= 0;
    end
    else begin
        xpos <= xpos_nxt;
        ypos <= ypos_nxt;
        t <= t_nxt;
    end
end

initial begin
    ypos = YPOS_INIT;
    xpos = XPOS_INIT;
end

/*always @(*) begin
        if ( ypos < 550 ) begin
            xpos_nxt = xpos;
            ypos_nxt = ypos+t+1;
            t_nxt = t+1;
        end
        else if ( ypos >= 550 ) begin
            xpos_nxt = xpos;
            ypos_nxt = ypos-t-1;
            t_nxt = t-1;
        end
        else begin
            xpos_nxt = xpos;
            ypos_nxt = ypos;
        end
end*/

/*
If clock 100 Hz is applied to the module, then t is incremented each 10 ms.
v = 1 pixels/10ms -> obstables moving 100 pixels in 1 sec
*/

always @* begin

    t_nxt = t + 1;

    case (state)

        DOWN: begin
              if (ypos > 500 ) begin
                ypos_nxt = YPOS_INIT + ypos + t;
                state_nxt =  CHANGE_DIRECTION;
                GO_UP = 1'b1;
              end
              else begin
                ypos_nxt = ypos + t + 1;
                state_nxt = DOWN;
                GO_UP = 1'b0;
              end
        end

        UP: begin
            if (ypos < 20 ) begin
                ypos_nxt = ypos - 1;
                state_nxt =  CHANGE_DIRECTION;
                GO_UP = 1'b0;
            end
            else begin
                ypos_nxt = YPOS_INIT - ypos - 1;
                state_nxt = DOWN;
                GO_UP = 1'b1;
            end
        end

        CHANGE_DIRECTION: begin
            ypos_nxt = ypos;
            state_nxt = GO_UP ? UP : DOWN;
            t_nxt = 1;
        end

    endcase
end

endmodule