Merged r5033:5116 from developer branch jcorgan/snd, with minor edits. Trunk passes...

[debian/gnuradio] / gr-sounder / src / fpga / lib / sounder_rx.v

diff --git a/gr-sounder/src/fpga/lib/sounder_rx.v b/gr-sounder/src/fpga/lib/sounder_rx.v
new file mode 100644 (file)
index 0000000..b7c5f48
--- /dev/null
+++ b/gr-sounder/src/fpga/lib/sounder_rx.v
@@ -0,0 +1,84 @@
+// -*- verilog -*-
+//
+//  USRP - Universal Software Radio Peripheral
+//
+//  Copyright (C) 2007 Corgan Enterprises 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 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., 51 Franklin Street, Boston, MA  02110-1301  USA
+//
+
+module sounder_rx(clk_i,rst_i,ena_i,rx_strobe_i,tx_strobe_i,mask_i,len_i,
+                 rx_in_i_i,rx_in_q_i,rx_i_o,rx_q_o,rx_strobe_o);
+   
+   input         clk_i;                // Master clock
+   input         rst_i;         // Subsystem reset
+   input         ena_i;                // Subsystem enable
+   input         rx_strobe_i;   // Strobe every received sample
+   input         tx_strobe_i;  // Strobe every transmitted sample
+    
+   input  [15:0] mask_i;       // PN code LFSR mask
+   input  [15:0] len_i;                // PN code LFSR sequence length
+   input  [15:0] rx_in_i_i;    // I channel on receive
+   input  [15:0] rx_in_q_i;    // Q channel on receive
+
+   output [15:0] rx_i_o;       // I channel of impulse response
+   output [15:0] rx_q_o;       // Q channel of impulse response
+   output        rx_strobe_o;   // Impulse response value ready
+
+   // LFSR phase counter
+   reg [15:0] count;
+   wire cycle = (count == (len_i - 1));
+
+   always @(posedge clk_i)
+     if (rst_i | ~ena_i)
+       count <= 16'b0;
+     else
+       if (cycle)
+        count <= 16'b0;
+       else
+        count <= count + 16'b1;
+           
+   // Retard LFSR phase once per cycle
+   wire lfsr_strobe = (tx_strobe_i & ~cycle);
+
+   // Recreate local reference of transmitted PN code
+   wire pn;
+   lfsr reference
+     ( .clk_i(clk_i),.rst_i(rst_i),.ena_i(ena_i),.strobe_i(lfsr_strobe),.mask_i(mask_i),.pn_o(pn) );
+
+   wire [31:0] rx_i_ext, rx_q_ext;
+   sign_extend #(16,32) i_extend(rx_in_i_i, rx_i_ext);
+   sign_extend #(16,32) q_extend(rx_in_q_i, rx_q_ext);
+
+   reg [31:0] accum;
+   always @(posedge clk_i)
+     if (rst_i | ~ena_i)
+       accum <= 32'b0;
+     else
+       if (rx_strobe_i)
+        if (cycle)
+          accum <= 32'b0;
+        else
+          if (pn)
+            accum <= accum + rx_i_ext;
+          else
+            accum <= accum - rx_i_ext;
+   
+   assign rx_i_o = accum[31:16];
+   assign rx_q_o = accum[15:0];
+   assign rx_strobe_o = rx_strobe_i & cycle;
+
+endmodule // sounder_rx
+