1 files changed, 68 insertions, 0 deletions
diff --git a/cocotb_try/cic3_pdm.v b/cocotb_try/cic3_pdm.v
new file mode 100644
index 0000000..f572d64
--- /dev/null
+++ b/cocotb_try/cic3_pdm.v
@@ -0,0 +1,68 @@
+
+// XXX: A chatbot wrote this, might be complete crack
+
+module cic3_pdm (
+    input  wire        clk,        // PDM clock
+    input  wire        rst,        // active-high synchronous reset
+    input  wire        pdm_in,     // 1-bit PDM data input
+    output wire signed [15:0] pcm_out, // Decimated PCM output
+    output wire        pcm_valid   // High when pcm_out is valid
+);
+    parameter DECIMATION = 64; // Decimation factor
+
+    // Internal registers
+    reg signed [31:0] integrator_0 = 0;
+    reg signed [31:0] integrator_1 = 0;
+    reg signed [31:0] integrator_2 = 0;
+
+    reg [5:0] decim_counter = 0;
+    reg signed [31:0] comb_0 = 0, comb_1 = 0, comb_2 = 0;
+    reg signed [31:0] delay_0 = 0, delay_1 = 0, delay_2 = 0;
+
+    reg signed [15:0] pcm_out_r = 0;
+    reg pcm_valid_r = 0;
+
+    // Integrator stage (runs every clk)
+    always @(posedge clk) begin
+        if (rst) begin
+            integrator_0 <= 0;
+            integrator_1 <= 0;
+            integrator_2 <= 0;
+        end else begin
+            integrator_0 <= integrator_0 + (pdm_in ? 1 : -1);
+            integrator_1 <= integrator_1 + integrator_0;
+            integrator_2 <= integrator_2 + integrator_1;
+        end
+    end
+
+    // Decimation counter
+    always @(posedge clk) begin
+        if (rst)
+            decim_counter <= 0;
+        else
+            decim_counter <= decim_counter + 1;
+    end
+
+    // Comb stage (runs every DECIMATION clocks)
+    always @(posedge clk) begin
+        pcm_valid_r <= 0;
+        if (decim_counter == DECIMATION[5:0] - 1) begin
+            comb_0 <= integrator_2 - delay_0;
+            delay_0 <= integrator_2;
+
+            comb_1 <= comb_0 - delay_1;
+            delay_1 <= comb_0;
+
+            comb_2 <= comb_1 - delay_2;
+            delay_2 <= comb_1;
+
+            // Bit-shift down to get 16-bit output (tune shift based on DECIMATION and stage count)
+            pcm_out_r <= comb_2[31:16]; 
+            pcm_valid_r <= 1;
+        end
+    end
+
+    assign pcm_out = pcm_out_r;
+    assign pcm_valid = pcm_valid_r;
+
+endmodule