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//
// Copyright 2011 Ettus Research LLC
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//
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
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