mictoled: improve sim test data

1 files changed, 103 insertions, 0 deletions

diff --git a/mictoled/mictoled.v b/mictoled/mictoled.v
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+++ b/mictoled/mictoled.v
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+/*
+ *  Copyright(C) 2024 Matthias P. Braendli <matthias.braendli@mpb.li>
+ *  Copyright(C) 2018 Gerald Coe, Devantech Ltd <gerry@devantech.co.uk>
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any purpose with or
+ *  without fee is hereby granted, provided that the above copyright notice and
+ *  this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO
+ *  THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS.
+ *  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
+ *  DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
+ *  AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ *  CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+// This is following the excellent explanation on
+// https://tomverbeure.github.io/2020/09/30/Moving-Average-and-CIC-Filters.html
+
+module mictoled
+    #(
+        parameter integer INTEGRATOR_WIDTH=16,
+        parameter integer COMB_WIDTH=12)
+    (
+        input clk, // 12MHz
+        input btn,
+
+        output mic_clk,
+        input mic_dat,
+
+        output led1, output led2, output led3, output led4,
+        output led5, output led6, output led7, output led8,
+        output lcol1, output lcol2, output lcol3, output lcol4
+    );
+    /* PDM mic clock gen */
+    reg [31:0] clkdiv = 8'b0;
+    always @ (posedge clk) begin
+        clkdiv <= (clkdiv + 1) % 24;
+    end
+
+    wire mic_strobe = clkdiv == 12;
+    assign mic_clk = clkdiv >= 12;
+
+    /* CIC decimator by 64 => 2MHz -> 31.25 kHz */
+    reg [INTEGRATOR_WIDTH-1:0] integrator = 0;
+    reg [5:0] decim_strobe_counter = 8'b0;
+    always @ (posedge clk) begin
+        if (mic_strobe) begin
+            if (mic_dat == 0)
+                integrator <= integrator + 1;
+            else
+                integrator <= integrator - 1;
+
+            decim_strobe_counter <= (decim_strobe_counter + 1) % 64;
+        end
+    end
+
+    /* Comb stage after decimation */
+    wire decim_strobe = decim_strobe_counter == 0 && mic_strobe;
+    reg [INTEGRATOR_WIDTH-1:0] previous_integrator = 0;
+    reg [COMB_WIDTH-1:0] comb_out = 0; // can be reduced_width
+    always @ (posedge clk) begin
+        if (decim_strobe) begin
+            comb_out = integrator - previous_integrator;
+            previous_integrator <= integrator;
+        end
+    end
+
+    /* Goertzel Algorithm to detect presence of frequencies */
+    // coef = 2 * cos(2 * PI * freq / sample_rate);
+    // 440 Hz  -> 1.992178649
+    // 1200 Hz -> 1.942068556
+    // Represent in fixed point in Q4.10, i.e. a scaling factor of 1024
+    //integer coef_440 = 2040; // 439.75 Hz
+    real coef_440 = 1.992178649;
+
+    real q1_440 = 0;
+    real q2_440 = 0;
+    reg [9:0] goertzel_strobe_counter = 0;
+
+    real m_squared_440 = 0;
+
+    always @ (posedge clk) begin
+        if (decim_strobe) begin
+            goertzel_strobe_counter <= goertzel_strobe_counter + 1; // overflow at 1024
+
+            if (goertzel_strobe_counter % 256 == 0) begin
+                m_squared_440 <= q1_440 * q1_440 + q2_440 * q2_440 - coef_440 * q1_440 * q2_440;
+                q1_440 <= 0;
+                q2_440 <= 0;
+            end
+            else begin
+                q1_440 <= coef_440 * q1_440 - q2_440 + comb_out;
+                q2_440 <= q1_440;
+            end
+        end
+    end
+
+    /* LED drivers - counter is inverted for display because leds are active low */
+    //assign {led8, led7, led6, led5, led4, led3, led2, led1} = m_squared_440[14:6] ^ 8'hff;
+    assign {lcol4, lcol3, lcol2, lcol1} = 4'b1110;
+
+endmodule