diff options
Diffstat (limited to 'gr-sounder/src/fpga/lib/sounder_rx.v')
| -rw-r--r-- | gr-sounder/src/fpga/lib/sounder_rx.v | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/gr-sounder/src/fpga/lib/sounder_rx.v b/gr-sounder/src/fpga/lib/sounder_rx.v new file mode 100644 index 000000000..b7c5f4878 --- /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 + |