add effect mixer module and posibility to switch effects

no_effect.v

@@ -0,0 +1,77 @@
+module no_effect #( parameter
+    data_width = 16          // data width 
+)(
+    input                                   clk,
+    input                                   reset,
+    input   signed      [data_width-1: 0]   i_data,
+    output  signed      [data_width-1: 0]   o_data,
+    input                                   i_read_done,
+    output                                  o_read_enable,
+    output                                  o_data_valid,
+    input                                   i_data_ready
+);
+
+//-------------Internal Constants---------------------------
+localparam [3:0]        IDLE         = 'd0,
+                        OUTPUT       = 'd1;
+
+reg [3:0] r_state=IDLE, r_next=IDLE;
+
+reg   signed      [data_width-1: 0]     r_data = 'b0;
+reg                                     r_read_enable = 0;
+reg                                     r_data_valid = 0;
+
+assign  o_read_enable   = r_read_enable;
+assign  o_data_valid    = r_data_valid;
+assign  o_data          = r_data;
+
+
+//---------state register sequential always block-----------
+always @(posedge clk ) begin
+    if (reset == 1) begin
+        // clear state
+        r_state <= IDLE;
+        r_next <= IDLE;
+    end
+    else begin
+        r_state <= r_next;
+    end 
+end
+
+//----next state & outputs, combinational always block------
+
+always @(posedge clk ) begin
+    
+    case(r_state)
+        IDLE    :   begin
+                        if (i_data_ready == 1) begin
+                            r_next <= OUTPUT;
+                            r_data <= i_data;
+                            r_read_enable <= 0;
+                            r_data_valid <= 0;
+                        end
+                        else begin
+                            r_next <= IDLE;
+                            r_read_enable <= 1;     // redy to read data
+                            r_data_valid <= 0;
+                        end                     
+                    end
+        OUTPUT  :   begin
+                        if (i_read_done == 1) begin
+                            r_next <= IDLE;
+                            r_data_valid <= 0;
+                            r_read_enable <= 1;
+                        end
+                        else begin
+                            r_next <= OUTPUT;
+                            r_data_valid <= 1;
+                            r_read_enable <= 0;     // read disable
+                        end
+                    end
+        default: r_next <= IDLE;          // on error
+    endcase 
+end
+
+
+
+endmodule