From e956f85190bbb6b8e82d80f1f06ac586fae4f780 Mon Sep 17 00:00:00 2001
From: Wojciech Kosior <kwojtus@protonmail.com>
Date: Thu, 2 Apr 2020 01:39:50 +0200
Subject: warmup before actual work

---
 src/example.v | 122 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 122 insertions(+)
 create mode 100644 src/example.v

(limited to 'src/example.v')

diff --git a/src/example.v b/src/example.v
new file mode 100644
index 0000000..bf90bbe
--- /dev/null
+++ b/src/example.v
@@ -0,0 +1,122 @@
+`default_nettype none
+  
+module vga_example(input wire 	    clock_100mhz,
+		   input wire 	    reset,
+		   
+		   output reg 	    h_sync,
+		   output reg 	    v_sync,
+		   output reg [2:0] vga_red,
+		   output reg [2:0] vga_green,
+		   output reg [2:0] vga_blue
+		   );
+   
+   wire [9:0] 			    col_next_tick;
+   wire [8:0] 			    row_next_tick;
+   wire 			    h_sync_next_tick;
+   wire 			    v_sync_next_tick;
+   wire 			    display_on_next_tick;
+   
+   vga vga(clock_100mhz, ~reset, h_sync_next_tick, v_sync_next_tick,
+	   col_next_tick, row_next_tick, display_on_next_tick);
+   
+   always @ (posedge clock_100mhz) begin
+      h_sync <= h_sync_next_tick;
+      v_sync <= v_sync_next_tick;
+      
+      if (display_on_next_tick) begin
+	 vga_red <= 3'b000;
+	 vga_green <= row_next_tick < 220 ? 3'b111 : 3'b000;
+	 vga_blue <= row_next_tick >= 220 ? 3'b111 : 3'b000;	 
+      end
+      else begin
+	 vga_red <= 0;
+	 vga_green <= 0;
+	 vga_blue <= 0;
+      end
+   end // always @ (posedge clock_100mhz)
+endmodule // vga_example
+
+module vga(input wire       clock_100mhz,
+	   input wire 	    reset,
+	   
+	   output reg 	    h_sync,
+	   output reg 	    v_sync,
+	   output reg [9:0] col,
+	   output reg [8:0] row,
+	   output reg 	    display_on);
+
+   parameter h_pixels = 640;
+   parameter v_pixels = 480;
+   parameter h_front_porch = 16;
+   parameter v_front_porch = 10;
+   parameter h_pulse = 96;
+   parameter v_pulse = 2;
+   parameter h_back_porch = 48;
+   parameter v_back_porch = 33;
+   parameter h_pol = 1'b0;
+   parameter v_pol = 1'b1;
+
+   parameter h_pulse_start = h_front_porch;
+   parameter v_pulse_start = v_front_porch;
+   parameter h_pulse_end = h_front_porch + h_pulse;
+   parameter v_pulse_end = v_front_porch + v_pulse;
+   parameter h_active_video_start = h_front_porch + h_pulse + h_back_porch;
+   parameter v_active_video_start = v_front_porch + v_pulse + v_back_porch;
+   parameter h_frame_end = h_active_video_start + h_pixels;
+   parameter v_frame_end = v_active_video_start + v_pixels;
+
+   reg [9:0] 		    h_counter;
+   reg [9:0] 		    v_counter;
+
+   reg [1:0] 		    divider; // 25MHz
+
+   always @ (posedge clock_100mhz) begin
+      if (reset) begin
+	 divider <= 2'b00;
+	 h_counter <= 0;
+	 v_counter <= 0;
+
+	 h_sync <= ~h_pol;
+	 v_sync <= ~v_pol;
+	 row <= 0;
+	 col <= 0;
+	 display_on <= 0;
+      end // if (reset)
+      else begin
+	 divider <= divider + 1;
+	 
+	 if (divider == 2'b11) begin
+	    display_on <= (h_counter < h_frame_end - 1) &&
+			  (h_counter >= h_active_video_start - 1) &&
+			  (v_counter < v_frame_end) &&
+			  (v_counter >= v_active_video_start);
+
+	    if (h_counter < h_frame_end - 1) begin
+	       h_counter <= h_counter + 1;
+
+	       h_sync <= h_pol ^ (h_counter < h_pulse_start - 1 || h_counter >= h_pulse_end - 1);
+	       
+	       if (h_counter >= h_active_video_start)
+		 col <= col + 1;
+	    end
+	    else begin
+	       h_counter <= 0;
+	       col <= 0;
+	       
+	       if (v_counter < v_frame_end - 1) begin
+		  v_counter <= v_counter + 1;
+
+		  v_sync <= v_pol ^ (v_counter < v_pulse_start - 1 || v_counter >= v_pulse_end - 1);
+
+		  if (v_counter >= v_active_video_start)
+		    row <= row + 1;
+	       end
+	       else begin
+		  v_counter <= 0;
+		  row <= 0;
+	       end // else: !if(v_counter < v_frame_end - 1)
+	    end // else: !if(h_counter < h_frame_end - 1)
+	 end // if (divider == 2'b11)
+      end // else: !if(reset)
+   end // always @ (posedge clock_100mhz)
+endmodule // vga
-- 
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