Adds alternative integrate and dump decimator to gr-gpio.

git-svn-id: http://gnuradio.org/svn/gnuradio/trunk@9009 221aa14e-8319-0410-a670-987f0aec2ac5

1 files changed, 75 insertions, 0 deletions

diff --git a/gr-gpio/src/fpga/lib/integrator.v b/gr-gpio/src/fpga/lib/integrator.v
new file mode 100644
index 000000000..22357a565
--- /dev/null
+++ b/gr-gpio/src/fpga/lib/integrator.v
@@ -0,0 +1,75 @@
+// -*- verilog -*-
+//
+//  USRP - Universal Software Radio Peripheral
+//
+//  Copyright (C) 2003 Matt Ettus
+//  Copyright (C) 2008 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
+//
+
+// Integrate and dump decimation filter
+// 
+// Functionally equivalent to single-stage CIC decimator, simpler code
+// Results in single sample impulse response at decimated rate
+
+module integrator
+  ( clock,reset,enable,rate,strobe_in,strobe_out,signal_in,signal_out);
+   parameter bw = 16;
+   parameter maxbitgain = 8;
+   
+   input       clock;
+   input       reset;
+   input       enable;
+   input [7:0] rate;
+   input       strobe_in;
+   input       strobe_out;	
+
+   input  [bw-1:0] signal_in;
+   wire   [bw-1:0] signal_out_unreg;
+   output [bw-1:0] signal_out;
+   reg    [bw-1:0] signal_out;
+
+   wire [bw+maxbitgain-1:0] signal_in_ext;
+   reg  [bw+maxbitgain-1:0] accum;
+   reg  [bw+maxbitgain-1:0] dump;
+
+   sign_extend #(bw,bw+maxbitgain) 
+      ext_input (.in(signal_in),.out(signal_in_ext));
+   
+   // Integrate samples, dump on strobe out
+   always @(posedge clock)
+     if (reset | ~enable)
+       begin
+	 accum <= 0;
+	 dump <= 0;
+       end
+     else if (enable && strobe_in)
+        if (~strobe_out)
+	   accum <= accum + signal_in_ext;
+        else
+	   begin
+	     dump <= accum;
+	     accum <= signal_in_ext;
+           end
+   
+   // Normalize for integration bit gain
+   integ_shifter #(bw)
+	shifter(rate,dump,signal_out_unreg);
+
+   always @(posedge clock)
+     signal_out <= #1 signal_out_unreg;
+   
+endmodule // integrator