diff options
Diffstat (limited to 'cocotb_try/cic3_pdm.v')
| -rw-r--r-- | cocotb_try/cic3_pdm.v | 31 |
1 files changed, 14 insertions, 17 deletions
diff --git a/cocotb_try/cic3_pdm.v b/cocotb_try/cic3_pdm.v index 0d7ba18..3d23d44 100644 --- a/cocotb_try/cic3_pdm.v +++ b/cocotb_try/cic3_pdm.v @@ -27,11 +27,7 @@ module cic3_pdm ( // DC removal filter registers reg signed [19:0] dc_accumulator; // 20-bit to prevent overflow - reg signed [15:0] dc_estimate; - /* verilator lint_off UNUSEDSIGNAL */ - // Lower 8 bits of alpha_mult unused - we only need [23:8] for division by 256 - reg signed [23:0] alpha_mult; // For alpha multiplication - /* verilator lint_on UNUSEDSIGNAL */ + wire signed [CIC_WIDTH-1:0] pdm_signed = pdm_in ? 17'sd1 : -17'sd1; @@ -96,30 +92,31 @@ module cic3_pdm ( always @(posedge clk) begin if (rst) begin dc_accumulator <= 20'sd0; - dc_estimate <= 16'sd0; - alpha_mult <= 24'sd0; pcm_out <= 0; pcm_valid <= 0; end else begin pcm_valid <= 0; if (cic_valid) begin - // Configurable DC removal using alpha parameter - // If dc_alpha = 0, bypass DC removal - // If dc_alpha = 255, strong DC removal (original /16 behavior) if (dc_alpha == 8'd0) begin // Bypass DC removal pcm_out <= scaled_out; end else begin - // Calculate alpha * dc_estimate / 256 - alpha_mult <= dc_estimate * dc_alpha; - dc_estimate <= dc_accumulator[19:4]; // Current estimate + // Calculate the updated accumulator value first + reg signed [19:0] new_accumulator; + case (dc_alpha) + 8'd1: new_accumulator = dc_accumulator - (dc_accumulator >>> 12) + {{4{scaled_out[15]}}, scaled_out}; + 8'd16: new_accumulator = dc_accumulator - (dc_accumulator >>> 8) + {{4{scaled_out[15]}}, scaled_out}; + 8'd64: new_accumulator = dc_accumulator - (dc_accumulator >>> 6) + {{4{scaled_out[15]}}, scaled_out}; + 8'd255: new_accumulator = dc_accumulator - (dc_accumulator >>> 4) + {{4{scaled_out[15]}}, scaled_out}; + default: new_accumulator = dc_accumulator - (dc_accumulator >>> 8) + {{4{scaled_out[15]}}, scaled_out}; + endcase - // Leaky integrator: acc = acc - (alpha/256)*acc + scaled_out - dc_accumulator <= dc_accumulator - {{4{alpha_mult[23]}}, alpha_mult[23:8]} + {{4{scaled_out[15]}}, scaled_out}; + // Update accumulator + dc_accumulator <= new_accumulator; - // Output with DC removal - pcm_out <= scaled_out - dc_estimate; + // Output = input - NEW DC estimate (not old one) + pcm_out <= scaled_out - new_accumulator[19:4]; end pcm_valid <= 1; end |