From 0434ba1d907755fe3057f1d2f2f1d487b02279b9 Mon Sep 17 00:00:00 2001
From: Jacob Lifshay <programmerjake@gmail.com>
Date: Tue, 27 Nov 2018 23:54:15 -0800
Subject: [PATCH] add instructions for using iverilog

---
 .gitignore  |  2 ++
 ReadMe.md   | 22 ++++++++++++++++++++++
 main_test.v | 14 +++++++++++++-
 3 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/.gitignore b/.gitignore
index 20598f5..ccb0f2e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -75,3 +75,5 @@
 /xlnx_auto_0_xdb
 /xst
 /output.bit
+/dump.vcd
+/rv32
diff --git a/ReadMe.md b/ReadMe.md
index e777adb..c204664 100644
--- a/ReadMe.md
+++ b/ReadMe.md
@@ -45,6 +45,28 @@ Requires Xilinx's ISE v. 14.7 to be installed in /opt/Xilinx (just leave the def
     # at this point the built bitstream is in output.bit
     djtgcfg prog -d JtagHS2 -i 0 -f output.bit # program the FPGA
 
+## Simulating using Icarus Verilog
+Doesn't require Xilinx's ISE or Digilent's programmer
+
+    sudo apt-get install git g++ autoconf automake autotools-dev curl libmpc-dev libmpfr-dev libgmp-dev gawk build-essential bison flex texinfo gperf libtool patchutils bc zlib1g-dev libexpat-dev
+    sudo mkdir /opt/riscv
+    sudo chown $USER /opt/riscv # so you don't need root when building; you can change back after building riscv-gnu-toolchain
+    git clone --recursive https://github.com/riscv/riscv-gnu-toolchain.git
+    export PATH=/opt/riscv/bin:"$PATH"
+    cd riscv-gnu-toolchain
+    ./configure --prefix=/opt/riscv --with-arch=rv32i
+    make
+    sudo chown -R root:root /opt/riscv # change owner back to root as the compiler is finished installing
+    cd ..
+    git clone https://github.com/programmerjake/rv32.git
+    cd rv32/software
+    make ram0_byte0.hex
+    cd ..
+    iveriog -o rv32 -Wall *.v
+    vvp -n rv32 # doesn't terminate, press Ctrl+C when it's generated enough output
+
+The output is in `dump.vcd`, which can be viewed with GTKWave.
+
 ## Building the hardware (only required if verilog source is modified)
 
 Requires having built the software at least once to generate the ram initialization files.
diff --git a/main_test.v b/main_test.v
index 404b101..12e6801 100644
--- a/main_test.v
+++ b/main_test.v
@@ -26,6 +26,8 @@ module main_test;
 
 	// Inputs
 	reg clk;
+	reg switch_2;
+	reg switch_3;
 
 	// Outputs
 	wire [7:0] vga_r;
@@ -35,6 +37,9 @@ module main_test;
 	wire vga_vsync;
 	wire vga_blank;
 	wire vga_pixel_clock;
+	wire led_1;
+	wire led_3;
+
 
 	// Instantiate the Unit Under Test (UUT)
 	main uut (
@@ -45,12 +50,19 @@ module main_test;
 		.vga_hsync(vga_hsync), 
 		.vga_vsync(vga_vsync), 
 		.vga_blank(vga_blank), 
-		.vga_pixel_clock(vga_pixel_clock)
+		.vga_pixel_clock(vga_pixel_clock),
+		.switch_2(switch_2),
+		.switch_3(switch_3),
+		.led_1(led_1),
+		.led_3(led_3)
 	);
 
 	initial begin
 		// Initialize Inputs
+		$dumpvars;
 		clk = 0;
+		switch_2 = 0;
+		switch_3 = 0;
 
 		// Add stimulus here
         
-- 
2.30.2