Hi everyone,

I have a basys2 digilent fpga card. I just want to draw a picture on the 
screen with VGA cable. The following is the code that I wrote. However, 
it is not working that I expect. Could you please help me about where 
the problem is? Thanks ..


`timescale 1ns / 1ps
////////////////////////////////////////////////////////////////////////
//////////
// Company:
// Engineer:
//
// Create Date:    15:41:47 05/18/2013
// Design Name:
// Module Name:    kodilk
// Project Name:
// Target Devices:
// Tool versions:
// Description:
//
// Dependencies:
//
// Revision:
// Revision 0.01 - File Created
// Additional Comments:
//
////////////////////////////////////////////////////////////////////////
//////////
module basla(clr,clk,hsync,vsync,red,green,blue);


  input wire clr;
  input wire clk; // This is for 50Mhz clock signal . Connect B8 pin
  output wire hsync;    //horizontal sync out
  output wire vsync;    //vertical sync out
  output reg [2:0] red;  //red vga output
  output reg [2:0] green; //green vga output
  output reg [1:0] blue;  //blue vga output

  // This block is reponsible of 25 Mhz clock generation.
  reg clk_pixel=0;
  always @ (posedge clk)
  begin

    clk_pixel <= ~clk_pixel ;  // clk_pixel is equal to 50/2=25 Mhz.

  end
  // Counting mechanism
  reg [9:0] hc;
  reg [9:0] vc;

  always @(posedge clk_pixel or posedge clr)


  begin
  if (clr == 1)
  begin
    hc <= 0;
    vc <= 0;
  end
  else
  begin
    if (hc < 799)
      hc <= hc + 1;
    else
    begin
      hc <= 0;
      if (vc < 524)
        vc <= vc + 1;
      else
        vc <= 0;
    end
  end
end



  // end of counting mechanism

  //sync pulses - active low-

  assign hsync = (hc < 96) ? 0:1;
  assign vsync = (vc < 2) ? 0:1;

  // lets draw some picture
    always @ (hc or vc)
    begin
      if (vc >34 && vc < 515)
      begin
      if (hc > 143 && hc < 700)
        begin
        red = 3'b111;
        green = 3'b000;
        blue= 2'b00;
        end

    end
    end

endmodule






Plus , ucf file:

CE: Start of Constraints generated by PACE

#PACE: Start of PACE I/O Pin Assignments
NET "blue[0]"  LOC = "H13"  ;
NET "blue[1]"  LOC = "J13"  ;
NET "clk"  LOC = "B8"  ;
NET "clr"  LOC = "N3"  ;
NET "green[0]"  LOC = "F14"  ;
NET "green[1]"  LOC = "G13"  ;
NET "green[2]"  LOC = "G14"  ;
NET "hsync"  LOC = "J14"  ;
NET "red[0]"  LOC = "C14"  ;
NET "red[1]"  LOC = "D13"  ;
NET "red[2]"  LOC = "F13"  ;
NET "vsync"  LOC = "K13"  ;

#PACE: Start of PACE Area Constraints

#PACE: Start of PACE Prohibit Constraints

#PACE: End of Constraints generated by PACE

I can see two clocks in your code, it may not be the problem,..
> always @ (posedge clk)
>  begin
>    clk_pixel <= ~clk_pixel ;  // clk_pixel is equal to 50/2=25 Mhz.

>always @(posedge clk_pixel or posedge clr)

.. but its better to use only one clock, for example:

1

 always @ (posedge clk)

2

  begin

3

    clk_pixe_en <= ~clk_pixel_en ;  // clk_pixel is equal to 50/2=25 Mhz.

4

    if (clk_pixe_en)

5

       begin

6

       // do something

7

       if (clr == 1)

8

       begin

9

          hc <= 0;

10

          vc <= 0

11

       // and so on

and here you create a logic loop or a latch, use a "else" for each "if"
to avoid that:
>// lets draw some picture
>    always @ (hc or vc)
>    begin
>      if (vc >34 && vc < 515)
>      begin
>      if (hc > 143 && hc < 700)
>        begin
>        red = 3'b111;
>        green = 3'b000;
>        blue= 2'b00;
>        end

1

      else

2

         red = ... 

3

   else

4

     red =

sir
i have verilog code for vga controler for fpga basys2. But i dont know 
how to use it. I maen how to run it without fpga. can we show ant output 
signal which will show mw my code is working properly.

please answer me asap.
thank you

i dont have test bench. I am using Xilinx software