Implement basic ascii framebuffer (read only for now)

dvi_test.xise

@@ -44,10 +44,6 @@
     <file xil_pn:name="main.ucf" xil_pn:type="FILE_UCF">
       <association xil_pn:name="Implementation" xil_pn:seqID="0"/>
     </file>
-    <file xil_pn:name="image_generator.vhd" xil_pn:type="FILE_VHDL">
-      <association xil_pn:name="BehavioralSimulation" xil_pn:seqID="154"/>
-      <association xil_pn:name="Implementation" xil_pn:seqID="7"/>
-    </file>
     <file xil_pn:name="keyboard.vhd" xil_pn:type="FILE_VHDL">
       <association xil_pn:name="BehavioralSimulation" xil_pn:seqID="153"/>
       <association xil_pn:name="Implementation" xil_pn:seqID="4"/>
@@ -56,6 +52,10 @@
       <association xil_pn:name="BehavioralSimulation" xil_pn:seqID="154"/>
       <association xil_pn:name="Implementation" xil_pn:seqID="1"/>
     </file>
+    <file xil_pn:name="font_rom.vhd" xil_pn:type="FILE_VHDL">
+      <association xil_pn:name="BehavioralSimulation" xil_pn:seqID="155"/>
+      <association xil_pn:name="Implementation" xil_pn:seqID="7"/>
+    </file>
   </files>
 
   <properties>

font.hex

@@ -0,0 +1,129 @@
+# IBM, Marcel Sondaar, Daniel Hepper bitmap font (public domain, https://github.com/dhepper/font8x8)
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+0000000000000000
+00180018183C3C18
+0000000000003636
+0036367F367F3636
+000C1F301E033E0C
+0063660C18336300
+006E333B6E1C361C
+0000000000030606
+00180C0606060C18
+00060C1818180C06
+0000663CFF3C6600
+00000C0C3F0C0C00
+060C0C0000000000
+000000003F000000
+000C0C0000000000
+000103060C183060
+003E676F7B73633E
+003F0C0C0C0C0E0C
+003F33061C30331E
+001E33301C30331E
+0078307F33363C38
+001E3330301F033F
+001E33331F03061C
+000C0C0C1830333F
+001E33331E33331E
+000E18303E33331E
+000C0C00000C0C00
+060C0C00000C0C00
+00180C0603060C18
+00003F00003F0000
+00060C1830180C06
+000C000C1830331E
+001E037B7B7B633E
+0033333F33331E0C
+003F66663E66663F
+003C66030303663C
+001F36666666361F
+007F46161E16467F
+000F06161E16467F
+007C66730303663C
+003333333F333333
+001E0C0C0C0C0C1E
+001E333330303078
+006766361E366667
+007F66460606060F
+0063636B7F7F7763
+006363737B6F6763
+001C36636363361C
+000F06063E66663F
+00381E3B3333331E
+006766363E66663F
+001E33380E07331E
+001E0C0C0C0C2D3F
+003F333333333333
+000C1E3333333333
+0063777F6B636363
+0063361C1C366363
+001E0C0C1E333333
+007F664C1831637F
+001E06060606061E
+00406030180C0603
+001E18181818181E
+0000000063361C08
+FF00000000000000
+0000000000180C0C
+006E333E301E0000
+003B66663E060607
+001E3303331E0000
+006E33333e303038
+001E033f331E0000
+000F06060f06361C
+1F303E33336E0000
+006766666E360607
+001E0C0C0C0E000C
+1E33333030300030
+0067361E36660607
+001E0C0C0C0C0C0E
+00636B7F7F330000
+00333333331F0000
+001E3333331E0000
+0F063E66663B0000
+78303E33336E0000
+000F06666E3B0000
+001F301E033E0000
+00182C0C0C3E0C08
+006E333333330000
+000C1E3333330000
+00367F7F6B630000
+0063361C36630000
+1F303E3333330000
+003F260C193F0000
+00380C0C070C0C38
+0018181800181818
+00070C0C380C0C07
+0000000000003B6E
+0000000000000000

font_rom.vhd

@@ -0,0 +1,87 @@
+library ieee;
+
+use ieee.std_logic_1164.all;
+use ieee.std_logic_unsigned.all;
+use ieee.numeric_std.all;
+
+use std.textio.all;
+use ieee.std_logic_textio.all;
+
+entity font_rom is
+    generic (
+        input_clk: integer
+    );
+    port (
+        clk: in std_logic;
+        x, y: in std_logic_vector(9 downto 0);
+
+        rgb: out std_logic_vector(23 downto 0)
+    );
+end font_rom;
+
+architecture logic of font_rom is
+    type rom_type is array(0 to 127) of std_logic_vector(63 downto 0);
+    type framebuffer_type is array(0 to 59, 0 to 79) of std_logic_vector(7 downto 0);
+
+    impure function read_font(filename: in string) return rom_type is
+        file rom_file: text is in filename;
+        variable rom_line: line;
+        variable rom: rom_type;
+    begin
+        -- skip comment in first line
+        readline(rom_file, rom_line);
+
+        for i in rom_type'range loop
+            readline(rom_file, rom_line);
+            hread(rom_line, rom(i));
+        end loop;
+
+        return rom;
+    end function;
+
+    constant font: rom_type := read_font("font.hex");
+
+    constant framebuffer: framebuffer_type := (
+        0 => (x"48", x"61", x"6C", x"6c", x"6f", others => x"00"),
+        1 to 59 => (others => x"00")
+    );
+
+    signal char_x: integer range 0 to 79;
+    signal char_y: integer range 0 to 59;
+    signal current_char: std_logic_vector(7 downto 0);
+
+    signal current_glyph: std_logic_vector(63 downto 0);
+    signal current_glyph_pos: integer range 0 to 127;
+
+    signal glyph_pos_raw: std_logic_vector(5 downto 0);
+    signal glyph_pos: integer range 0 to 63;
+begin
+
+    char_x <= to_integer(unsigned(x(9 downto 3)));
+    char_y <= to_integer(unsigned(y(9 downto 3)));
+
+    process(clk) is
+    begin
+        if rising_edge(clk) then
+            current_char <= framebuffer(char_y, char_x);
+        end if;
+    end process;
+
+    current_glyph_pos <= to_integer(unsigned(current_char));
+
+    process(clk) is
+    begin
+        if rising_edge(clk) then
+            current_glyph <= font(current_glyph_pos);
+        end if;
+    end process;
+
+    glyph_pos_raw <= y(2 downto 0) & x(2 downto 0);
+    glyph_pos <= to_integer(unsigned(glyph_pos_raw));
+
+    -- actually currently BRG
+    rgb <=
+        "111111111111111111111111" when current_glyph(glyph_pos) = '1' else
+        "000000000000000000000000";
+
+end logic;

main.vhd

@@ -85,14 +85,12 @@ begin
         dvi_de => de
     );
 
-    image_generator_i: entity work.image_generator generic map (
+    framebuffer: entity work.font_rom generic map (
         input_clk => 48_000_000
     ) port map (
         clk => clk_vga,
         x => image_x,
         y => image_y,
-        ctrl_up => rotary_up,
-        ctrl_down => rotary_down,
         rgb => pixel_rgb
     );