From 46e2f6b37c17200500f2a114590ad540bcc3c0e5 Mon Sep 17 00:00:00 2001
From: Julian Blake Kongslie
Date: Sun, 31 Oct 2021 12:25:15 -0700
Subject: Really simple switch debounce.

---
 hdl/panel.sv | 93 +++++++++++++++++++++++++++++++++++++-----------------------
 1 file changed, 57 insertions(+), 36 deletions(-)

(limited to 'hdl/panel.sv')

diff --git a/hdl/panel.sv b/hdl/panel.sv
index 5d47484..2e36974 100644
--- a/hdl/panel.sv
+++ b/hdl/panel.sv
@@ -1,6 +1,8 @@
 `include "util.svh"
 
 module panel
+    #(  DEBOUNCE_MAX    = 100
+    )
     (   input   bit clk
     ,   input   bit reset
 
@@ -12,6 +14,8 @@ module panel
     ,   inout   wire [40:31] gpioc
     );
 
+localparam DEBOUNCE_BITS = $clog2(DEBOUNCE_MAX+1);
+
 enum
     {   LED_ROW1
     ,   DEAD_ROW2
@@ -35,6 +39,9 @@ enum
     ,   SWITCH_ROW3
     } state;
 
+bit [3:1][12:1] switch_raw;
+bit [DEBOUNCE_BITS-1:0] switch_debounce;
+
 `define LEDROW1 gpioc[38]
 `define LEDROW2 gpioc[40]
 `define LEDROW3 gpiob[15]
@@ -82,8 +89,12 @@ always_ff @(posedge clk) begin
 
     if (reset) begin
         switch = 0;
+        switch_raw = 0;
+        switch_debounce = 0;
         state = state.first;
     end else begin
+        automatic bit [3:1][12:1] new_switch = switch_raw;
+
         case (state)
 `ifdef DO_LEDS
 `define LED_ROW(n) \
@@ -134,50 +145,50 @@ always_ff @(posedge clk) begin
             SWITCH_ROW1: begin
                 `SWROW2 = 1'b0;
 
-                switch[1][1]    = ~`COL1;
-                switch[1][2]    = ~`COL2;
-                switch[1][3]    = ~`COL3;
-                switch[1][4]    = ~`COL4;
-                switch[1][5]    = ~`COL5;
-                switch[1][6]    = ~`COL6;
-                switch[1][7]    = ~`COL7;
-                switch[1][8]    = ~`COL8;
-                switch[1][9]    = ~`COL9;
-                switch[1][10]   = ~`COL10;
-                switch[1][11]   = ~`COL11;
-                switch[1][12]   = ~`COL12;
+                new_switch[1][1]    = ~`COL1;
+                new_switch[1][2]    = ~`COL2;
+                new_switch[1][3]    = ~`COL3;
+                new_switch[1][4]    = ~`COL4;
+                new_switch[1][5]    = ~`COL5;
+                new_switch[1][6]    = ~`COL6;
+                new_switch[1][7]    = ~`COL7;
+                new_switch[1][8]    = ~`COL8;
+                new_switch[1][9]    = ~`COL9;
+                new_switch[1][10]   = ~`COL10;
+                new_switch[1][11]   = ~`COL11;
+                new_switch[1][12]   = ~`COL12;
             end
 
             SWITCH_ROW2: begin
                 `SWROW3 = 1'b0;
 
-                switch[2][1]    = ~`COL1;
-                switch[2][2]    = ~`COL2;
-                switch[2][3]    = ~`COL3;
-                switch[2][4]    = ~`COL4;
-                switch[2][5]    = ~`COL5;
-                switch[2][6]    = ~`COL6;
-                switch[2][7]    = ~`COL7;
-                switch[2][8]    = ~`COL8;
-                switch[2][9]    = ~`COL9;
-                switch[2][10]   = ~`COL10;
-                switch[2][11]   = ~`COL11;
-                switch[2][12]   = ~`COL12;
+                new_switch[2][1]    = ~`COL1;
+                new_switch[2][2]    = ~`COL2;
+                new_switch[2][3]    = ~`COL3;
+                new_switch[2][4]    = ~`COL4;
+                new_switch[2][5]    = ~`COL5;
+                new_switch[2][6]    = ~`COL6;
+                new_switch[2][7]    = ~`COL7;
+                new_switch[2][8]    = ~`COL8;
+                new_switch[2][9]    = ~`COL9;
+                new_switch[2][10]   = ~`COL10;
+                new_switch[2][11]   = ~`COL11;
+                new_switch[2][12]   = ~`COL12;
             end
 
             SWITCH_ROW3: begin
-                switch[3][1]    = ~`COL1;
-                switch[3][2]    = ~`COL2;
-                switch[3][3]    = ~`COL3;
-                switch[3][4]    = ~`COL4;
-                switch[3][5]    = ~`COL5;
-                switch[3][6]    = ~`COL6;
-                switch[3][7]    = ~`COL7;
-                switch[3][8]    = ~`COL8;
-                switch[3][9]    = ~`COL9;
-                switch[3][10]   = ~`COL10;
-                switch[3][11]   = ~`COL11;
-                switch[3][12]   = ~`COL12;
+                new_switch[3][1]    = ~`COL1;
+                new_switch[3][2]    = ~`COL2;
+                new_switch[3][3]    = ~`COL3;
+                new_switch[3][4]    = ~`COL4;
+                new_switch[3][5]    = ~`COL5;
+                new_switch[3][6]    = ~`COL6;
+                new_switch[3][7]    = ~`COL7;
+                new_switch[3][8]    = ~`COL8;
+                new_switch[3][9]    = ~`COL9;
+                new_switch[3][10]   = ~`COL10;
+                new_switch[3][11]   = ~`COL11;
+                new_switch[3][12]   = ~`COL12;
             end
 `endif
         endcase
@@ -186,6 +197,16 @@ always_ff @(posedge clk) begin
             state = state.first;
         else
             state = state.next;
+
+        if (new_switch == switch_raw) begin
+            if (switch_debounce == 0)
+                switch = switch_raw;
+            else
+                --switch_debounce;
+        end else begin
+            switch_raw = new_switch;
+            switch_debounce = DEBOUNCE_MAX;
+        end
     end
 end
 
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