Houston, we have a trunk.

git-svn-id: http://gnuradio.org/svn/gnuradio/trunk@3122 221aa14e-8319-0410-a670-987f0aec2ac5

1 files changed, 97 insertions, 0 deletions

diff --git a/usrp/fpga/sdr_lib/ddc.v b/usrp/fpga/sdr_lib/ddc.v
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+++ b/usrp/fpga/sdr_lib/ddc.v
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+// -*- verilog -*-
+//
+//  USRP - Universal Software Radio Peripheral
+//
+//  Copyright (C) 2003 Matt Ettus
+//
+//  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 2 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, write to the Free Software
+//  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+//
+
+
+
+// DDC block
+
+module ddc(input clock,
+			input reset,
+			input enable,
+			input [3:0] rate1,
+			input [3:0] rate2,
+			output strobe,
+			input [31:0] freq,
+			input [15:0] i_in,
+			input [15:0] q_in,
+			output [15:0] i_out,
+			output [15:0] q_out
+			);
+   parameter bw = 16;
+   parameter zw = 16;
+
+	wire [15:0] i_cordic_out, q_cordic_out;
+	wire [31:0] phase;
+
+	wire strobe1, strobe2;
+	reg [3:0] strobe_ctr1,strobe_ctr2;
+
+	always @(posedge clock)
+		if(reset | ~enable)
+			strobe_ctr2 <= #1 4'd0;
+		else if(strobe2)
+			strobe_ctr2 <= #1 4'd0;
+		else	
+			strobe_ctr2 <= #1 strobe_ctr2 + 4'd1;
+				
+	always @(posedge clock)
+		if(reset | ~enable)
+			strobe_ctr1 <= #1 4'd0;
+		else if(strobe1)
+			strobe_ctr1 <= #1 4'd0;
+		else if(strobe2)
+			strobe_ctr1 <= #1 strobe_ctr1 + 4'd1;
+				
+
+	assign strobe2 = enable & ( strobe_ctr2 == rate2 );
+	assign strobe1 = strobe2 & ( strobe_ctr1 == rate1 );
+
+	assign strobe = strobe1;
+
+	function [2:0] log_ceil;
+	input [3:0] val;
+	
+		log_ceil = val[3] ? 3'd4 : val[2] ? 3'd3 : val[1] ? 3'd2 : 3'd1; 
+	endfunction	
+	
+	wire [2:0] shift1 = log_ceil(rate1);
+	wire [2:0] shift2 = log_ceil(rate2);
+	
+	cordic #(.bitwidth(bw),.zwidth(zw),.stages(16))
+		cordic(.clock(clock), .reset(reset), .enable(enable),
+			.xi(i_in), .yi(q_in), .zi(phase[31:32-zw]), 
+			.xo(i_cordic_out), .yo(q_cordic_out), .zo()  );
+		
+	cic_decim_2stage #(.bw(bw),.N(4)) 
+		decim_i(.clock(clock),.reset(reset),.enable(enable),
+			.strobe1(1'b1),.strobe2(strobe2),.strobe3(strobe1),.shift1(shift2),.shift2(shift1),
+			.signal_in(i_cordic_out),.signal_out(i_out));
+			
+	cic_decim_2stage #(.bw(bw),.N(4)) 
+		decim_q(.clock(clock),.reset(reset),.enable(enable),
+			.strobe1(1'b1),.strobe2(strobe2),.strobe3(strobe1),.shift1(shift2),.shift2(shift1),
+			.signal_in(q_cordic_out),.signal_out(q_out));
+	
+	phase_acc #(.resolution(32))
+		nco (.clk(clock),.reset(reset),.enable(enable),
+			.freq(freq),.phase(phase));
+		
+endmodule