add video ram and make character generation more sophisticated

Author: jac-oblong

.gitignore

@@ -20,3 +20,4 @@ jml-8-mini/schematic/*.step
 **/*.FCBak
 **/*.o
 **/*.fs
+**/waveform/*

peripherals/jml-8-mini-vga/src/Makefile

@@ -16,29 +16,29 @@ all : make_clean toplevel.fs
 
 # Synthesis
 toplevel.json : $(SRCS)
-	@yosys -p "read_verilog $(SRCS); synth_gowin -top toplevel -json toplevel.json"
+	yosys -q -p "read_verilog $(SRCS); synth_gowin -top toplevel -json toplevel.json"
 
 # Place and Route
 toplevel_pnr.json : toplevel.json
-	@nextpnr-gowin --json toplevel.json --freq 27 --write \
+	nextpnr-gowin -q --json toplevel.json --freq 27 --write \
 		toplevel_pnr.json --device ${DEVICE} --family ${FAMILY} \
 		--cst ${BOARD}.cst
 
 # Generate Bitstream
 toplevel.fs : toplevel_pnr.json
-	@gowin_pack -d ${FAMILY} -o toplevel.fs toplevel_pnr.json
+	gowin_pack -d ${FAMILY} -o toplevel.fs toplevel_pnr.json
 
 # Programming Board
 program : toplevel.fs
-	@openFPGALoader -b ${BOARD} toplevel.fs -f
+	openFPGALoader -b ${BOARD} toplevel.fs -f
 
 
 # Testing
 %_tb.o : $(TB_DIR)/%_tb.v $(SRCS)
-	@iverilog -o $@ -s test $(SRCS) $<
+	iverilog -o $@ -s test $(SRCS) $<
 
 $(WAVE_DIR)/%.vcd : %_tb.o
-	@vvp $< -o $@
+	vvp $< -o $@
 
 test : $(WAVES)
 

peripherals/jml-8-mini-vga/src/charmem.v

@@ -0,0 +1,14 @@
+module charrom (
+    input [7:0] addr,
+    input [2:0] row,
+
+    output [7:0] pixels
+);
+
+   reg [7:0] chars[255:0][7:0];
+
+   initial $readmemh("charrom.txt", chars, 0);
+
+   assign pixels = chars[addr][row];
+
+endmodule

…ripherals/jml-8-mini-vga/src/charmem.txt …ripherals/jml-8-mini-vga/src/charrom.txtperipherals/jml-8-mini-vga/src/charmem.txt renamed to peripherals/jml-8-mini-vga/src/charrom.txt peripherals/jml-8-mini-vga/src/charmem.txt renamed to peripherals/jml-8-mini-vga/src/charrom.txt

@@ -1,8 +1,9 @@
-module chargen (
-    input        clk,
-    input  [7:0] character,
-    input  [2:0] vertcount,
-    output       pixel
+module pixelgen (
+    input       clk,
+    input [7:0] character,
+    input [2:0] vertoffset,
+
+    output pixel
 );
 
    reg  [2:0] index = 0;
@@ -12,10 +13,9 @@ module chargen (
 
    always @(posedge clk) index <= index + 1;
 
-   charmem #() character_rom (
-       .clk(clk),
+   charrom #() character_rom (
        .addr(character),
-       .row(vertcount[2:0]),
+       .row(vertoffset),
        .pixels(pixels)
    );
 

peripherals/jml-8-mini-vga/src/charrom.v

@@ -1,7 +1,7 @@
 `timescale 1 ns / 1 ns
 
 module test ();
-   reg  clk = 0;
+   reg  clk = 1;
    wire hsync;
    wire vsync;
 

peripherals/jml-8-mini-vga/src/chargen.v peripherals/jml-8-mini-vga/src/pixelgen.vperipherals/jml-8-mini-vga/src/chargen.v renamed to peripherals/jml-8-mini-vga/src/pixelgen.v

@@ -1,7 +1,7 @@
 `timescale 1 ns / 1 ns
 
 module test ();
-   reg  clk = 0;
+   reg  clk = 1;
    wire hsync;
    wire vsync;
    wire red;

peripherals/jml-8-mini-vga/src/testbench/signalgen_tb.v

@@ -11,7 +11,7 @@ module toplevel (
 
    wire pixel;
    wire visible;
-   reg [7:0] character = 65;
+   wire [7:0] character;
    wire [9:0] vertcount;
    wire [9:0] horicount;
 
@@ -20,11 +20,6 @@ module toplevel (
    assign blue  = pixel;
    assign lum   = pixel;
 
-   always @(posedge horicount[2]) begin
-      if (character == 65) character <= 32;
-      if (character == 32) character <= 65;
-   end
-
    signalgen #() signal_generator (
        .clk(clk),
        .vsync(vsync),
@@ -34,11 +29,18 @@ module toplevel (
        .horicount(horicount)
    );
 
-   chargen #() character_generator (
+   pixelgen #() character_generator (
        .clk(clk),
        .character(character),
-       .vertcount(vertcount[2:0]),
+       .vertoffset(vertcount[2:0]),
        .pixel(pixel)
    );
 
+   videocont #() video_controller (
+       .visible  (visible),
+       .horicount(horicount[9:3]),
+       .vertcount(vertcount[8:3]),
+       .character(character)
+   );
+
 endmodule

peripherals/jml-8-mini-vga/src/testbench/toplevel_tb.v

@@ -0,0 +1,16 @@
+module videocont (
+    input visible,
+    input [6:0] horicount,
+    input [5:0] vertcount,
+
+    output [7:0] character
+);
+
+   reg [7:0] videoram[59:0][79:0];
+
+   initial $readmemh("videoram.txt", videoram, 0);
+
+   assign character = visible ? videoram[vertcount][horicount] : 0;
+
+
+endmodule