From 22792c1300843ae4556dcf5cc4e771d97a6c1414 Mon Sep 17 00:00:00 2001
From: Jens True <jens.chr.true@gmail.com>
Date: Sun, 11 Nov 2018 10:25:27 +0100
Subject: [PATCH] Original import

---
 vga640x480.v | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)
 create mode 100644 vga640x480.v

diff --git a/vga640x480.v b/vga640x480.v
new file mode 100644
index 0000000..42e91f3
--- /dev/null
+++ b/vga640x480.v
@@ -0,0 +1,78 @@
+// FPGA VGA Graphics Part 1: 640x480 60Hz VGA Driver
+// (C)2017-2018 Will Green - Licensed under the MIT License
+// Learn more at https://timetoexplore.net/blog/arty-fpga-vga-verilog-01
+
+// For 60 Hz VGA i_pix_stb must be 25 MHz or 25.175 MHz
+// Details in tutorial: https://timetoexplore.net/blog/arty-fpga-vga-verilog-01
+
+`default_nettype none
+
+module vga640x480(
+    input wire i_clk,           // base clock
+    input wire i_pix_stb,       // pixel clock strobe
+    input wire i_rst,           // reset: restarts frame
+    output wire o_hs,           // horizontal sync
+    output wire o_vs,           // vertical sync
+    output wire o_blanking,     // high during blanking interval
+    output wire o_active,       // high during active pixel drawing
+    output wire o_screenend,    // high for one tick at the end of screen
+    output wire o_animate,      // high for one tick at end of active drawing
+    output wire [9:0] o_x,      // current pixel x position
+    output wire [8:0] o_y       // current pixel y position
+    );
+
+    // VGA timings https://timetoexplore.net/blog/video-timings-vga-720p-1080p
+    localparam HS_STA = 16;              // horizontal sync start
+    localparam HS_END = 16 + 96;         // horizontal sync end
+    localparam HA_STA = 16 + 96 + 48;    // horizontal active pixel start
+    localparam VS_STA = 480 + 11;        // vertical sync start
+    localparam VS_END = 480 + 11 + 2;    // vertical sync end
+    localparam VA_END = 480;             // vertical active pixel end
+    localparam LINE   = 800;             // complete line (pixels)
+    localparam SCREEN = 524;             // complete screen (lines)
+
+    reg [9:0] h_count;  // line position
+    reg [9:0] v_count;  // screen position
+
+    // generate sync signals (active low for 640x480)
+    assign o_hs = ~((h_count >= HS_STA) & (h_count < HS_END));
+    assign o_vs = ~((v_count >= VS_STA) & (v_count < VS_END));
+
+    // keep x and y bound within the active pixels
+    assign o_x = (h_count < HA_STA) ? 0 : (h_count - HA_STA);
+    assign o_y = (v_count >= VA_END) ? (VA_END - 1) : (v_count);
+
+    // blanking: high within the blanking period
+    assign o_blanking = ((h_count < HA_STA) | (v_count > VA_END - 1));
+
+    // active: high during active pixel drawing
+    assign o_active = ~((h_count < HA_STA) | (v_count > VA_END - 1)); 
+
+    // screenend: high for one tick at the end of the screen
+    assign o_screenend = ((v_count == SCREEN - 1) & (h_count == LINE));
+
+    // animate: high for one tick at the end of the final active pixel line
+    assign o_animate = ((v_count == VA_END - 1) & (h_count == LINE));
+
+    always @ (posedge i_clk)
+    begin
+        if (i_rst)  // reset to start of frame
+        begin
+            h_count <= 0;
+            v_count <= 0;
+        end
+        if (i_pix_stb)  // once per pixel
+        begin
+            if (h_count == LINE)  // end of line
+            begin
+                h_count <= 0;
+                v_count <= v_count + 1;
+            end
+            else 
+                h_count <= h_count + 1;
+
+            if (v_count == SCREEN)  // end of screen
+                v_count <= 0;
+        end
+    end
+endmodule