move stuff around

1 files changed, 53 insertions, 0 deletions

diff --git a/playground/debounce.v b/playground/debounce.v
new file mode 100644
index 0000000..33dc22e
--- /dev/null
+++ b/playground/debounce.v
@@ -0,0 +1,53 @@
+`timescale 1us/1us
+
+module debounce (
+  input rst_i,
+  input clk_i,
+  input signal_i,
+  output reg signal_o
+);
+
+// number of rising clock edges a signal needs to be stable
+// for it to be output.
+// (+1 for propagation).
+parameter STABLE_PERIOD = 50;
+parameter INIT_SIG_STATE = 1'b1;
+
+reg [31:0] clk_counter;
+reg prev_state;
+
+always @(posedge clk_i or negedge rst_i) begin
+  if (!rst_i) begin
+    // Learning: I would like to set the output to the input on reset
+    // but then I get
+    // Warning: Async reset value `\signal_i' is not constant!
+    // and a synthesis error.
+    clk_counter <= 0;
+    prev_state <= INIT_SIG_STATE;
+    signal_o <= INIT_SIG_STATE;
+  end else begin
+
+    if (signal_i != prev_state) begin
+      clk_counter <= 0;
+      prev_state <= signal_i;
+    end else begin
+      clk_counter <= clk_counter + 1;
+    end
+
+    if (clk_counter === STABLE_PERIOD) begin
+      signal_o <= signal_i;
+    end
+  end
+end
+
+// Learning?
+// Apparently, (and obviously, when you think about it),
+// it's not possible to drive a signal by two blocks
+// always @(signal_i) begin
+//   if (signal_i != prev_state) begin
+//     clk_counter <= 0;
+//     prev_state <= signal_i;
+//   end
+// end
+
+endmodule