From e284e518ed9be784714120c693c29616b22862d3 Mon Sep 17 00:00:00 2001
From: Nam Tran <thnam.me@gmail.com>
Date: Fri, 23 Oct 2020 15:50:04 -0500
Subject: [PATCH] led walker

---
 fsm/rtl/top.v  | 33 +++++++++++++++++++++++++++++++++
 fsm/sim/top.cc |  8 ++++----
 2 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/fsm/rtl/top.v b/fsm/rtl/top.v
index d4acbd3..fe786af 100644
--- a/fsm/rtl/top.v
+++ b/fsm/rtl/top.v
@@ -16,6 +16,7 @@ module top(i_clk, o_led, lcol1);
 
    reg [WIDTH-1:0] counter;
    reg [7:0] obuf; // output buffer, take into account the icefun use active low LED
+   reg [3:0] led_index;
    reg strobe;
 
    initial begin
@@ -26,11 +27,43 @@ module top(i_clk, o_led, lcol1);
    always @(posedge clk_12MHz)
       {strobe, counter} <= counter + 1'b1;
 
+   // fsm
+   always @(posedge clk_12MHz) begin
+      if (strobe) // led_index change only when strobe is 1
+         if (led_index >= 4'hd)
+            led_index <= 0;
+         else
+            led_index <= led_index + 1'b1;
+
+      case (led_index)
+         4'h0: obuf <= 8'h01;
+         4'h1: obuf <= 8'h02;
+         4'h2: obuf <= 8'h04;
+         4'h3: obuf <= 8'h08;
+         4'h4: obuf <= 8'h10;
+         4'h5: obuf <= 8'h20;
+         4'h6: obuf <= 8'h40;
+         4'h7: obuf <= 8'h80;
+         4'h8: obuf <= 8'h40;
+         4'h9: obuf <= 8'h20;
+         4'ha: obuf <= 8'h10;
+         4'hb: obuf <= 8'h08;
+         4'hc: obuf <= 8'h04;
+         4'hd: obuf <= 8'h02;
+         default : begin
+            obuf <= 8'h01;
+         end
+      endcase
+   end
+
+   /* shift reg
    // shifting bit
    always @(posedge clk_12MHz)
       if (strobe)
          obuf <= {obuf[6:0], obuf[7]}; // left shift
          // obuf <= {obuf[0], obuf[7:1]}; // right shift
+   */
+
 
    always @(posedge clk_12MHz)
       o_led <= ~obuf;
diff --git a/fsm/sim/top.cc b/fsm/sim/top.cc
index 7af96ef..00b13e3 100644
--- a/fsm/sim/top.cc
+++ b/fsm/sim/top.cc
@@ -35,12 +35,12 @@ int main(int argc, char **argv) {
 	unsigned tickcount = 0;
   int last_led = tb->o_led;
 
-	for(int k=0; k<(1 << 14); k++) {
+	for(int k=0; k<(1 << 16); k++) {
     tick(++tickcount, tb, tfp);
 
-    if (last_led != tb->o_led) {
-      printf("k = %7d, led = %d\n", k, tb->o_led);
-    }
+    // if (last_led != tb->o_led) {
+      // printf("k = %7d, led = %d\n", k, tb->o_led);
+    // }
 
     last_led = tb->o_led;
 	}