add basic example

hdl/tb/tb.gtkw

@@ -0,0 +1,36 @@
+[*]
+[*] GTKWave Analyzer v3.3.86 (w)1999-2017 BSI
+[*] Fri Jul  2 06:30:08 2021
+[*]
+[dumpfile] "/home/brendan/Documents/Projects/0042_ice40/hdl/tb.vcd"
+[dumpfile_mtime] "Fri Jul  2 06:30:05 2021"
+[dumpfile_size] 29504
+[savefile] "/home/brendan/Documents/Projects/0042_ice40/hdl/tb/tb.gtkw"
+[timestart] 0
+[size] 1920 1052
+[pos] -1 -1
+*-19.000000 765000 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
+[treeopen] tb.
+[treeopen] tb.top.
+[sst_width] 233
+[signals_width] 279
+[sst_expanded] 1
+[sst_vpaned_height] 656
+@28
+tb.clk
+tb.reset
+@c08022
+tb.led[7:0]
+@28
+(0)tb.led[7:0]
+(1)tb.led[7:0]
+(2)tb.led[7:0]
+(3)tb.led[7:0]
+(4)tb.led[7:0]
+(5)tb.led[7:0]
+(6)tb.led[7:0]
+(7)tb.led[7:0]
+@1401200
+-group_end
+[pattern_trace] 1
+[pattern_trace] 0

hdl/tb/tb.v

@@ -0,0 +1,37 @@
+// Author:  Brendan Haines
+// Date:    2021-07-02
+
+`timescale 1ns/1ps
+
+module tb();
+
+reg clk, reset;
+wire [7:0] led;
+
+top top(
+    .clk(clk),
+    .n_reset(~reset),
+    .led(led)
+);
+
+always #5 clk = ~clk;
+
+initial begin
+    $dumpfile("tb.vcd");
+    $dumpvars(0, tb);
+
+    clk = 0;
+    reset = 1;
+
+    #10
+    reset = 0;
+
+    #2560
+    // #2560
+    $display("----------");
+    $display("Finished simulation.");
+    $display("Simulation time:\t%d ns", $realtime);
+    $finish;
+end
+
+endmodule