1 files changed, 43 insertions, 0 deletions
diff --git a/sdr_lib/rx_dcoffset.v b/sdr_lib/rx_dcoffset.v
new file mode 100644
index 000000000..bedbd40e6
--- /dev/null
+++ b/sdr_lib/rx_dcoffset.v
@@ -0,0 +1,43 @@
+
+
+module rx_dcoffset 
+  #(parameter WIDTH=14,
+    parameter ADDR=8'd0)
+    (input clk, input rst, 
+     input set_stb, input [7:0] set_addr, input [31:0] set_data,
+     input signed [WIDTH-1:0] adc_in, output signed [WIDTH-1:0] adc_out);
+
+   // Because of some extra delays to make timing easier, the transfer function is:
+   //     (z-1)/(z^2-z-alpha)  where alpha is 1/2^n
+   
+   wire 	       set_now = set_stb & (ADDR == set_addr);
+   
+   reg 		       fixed;  // uses fixed offset
+   wire 	       signed [WIDTH-1:0] fixed_dco;
+   reg 		       signed [31:0] integrator;
+
+   always @(posedge clk)
+     if(rst)
+       begin
+	  fixed <= 0;
+	  integrator <= 32'd0;
+       end
+     else if(set_now)
+       begin
+	  integrator <= {set_data[WIDTH-1:0],{(32-WIDTH){1'b0}}};
+	  fixed <= set_data[31];
+       end
+     else if(~fixed)
+       integrator <= integrator + adc_out;
+   
+   wire [WIDTH:0] scaled_integrator;
+   
+   round #(.bits_in(33),.bits_out(15)) round (.in({integrator[31],integrator}),.out(scaled_integrator));
+   
+   wire [WIDTH:0]      adc_out_int = {adc_in[WIDTH-1],adc_in} - scaled_integrator;
+
+   clip_reg #(.bits_in(WIDTH+1),.bits_out(WIDTH)) clip_adc
+     (.clk(clk),.in(adc_out_int),.out(adc_out));
+   
+
+endmodule // rx_dcoffset