//
// Copyright 2011-2013 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/>.
//

//! The USRP digital up-conversion chain

module duc_chain
  #(
    parameter BASE = 0,
    parameter DSPNO = 0,
    parameter WIDTH = 24
  )
  (input clk, input rst, input clr,
   input set_stb, input [7:0] set_addr, input [31:0] set_data,

   // To TX frontend
   output [WIDTH-1:0] tx_fe_i,
   output [WIDTH-1:0] tx_fe_q,

   // From TX control
   input [31:0] sample,
   input run,
   output strobe,
   output [31:0] debug
   );

   wire [17:0] scale_factor;
   wire [31:0] phase_inc;
   reg [31:0]  phase;
   wire [7:0]  interp_rate;
   wire [3:0]  tx_femux_a, tx_femux_b;
   wire        enable_hb1, enable_hb2;
   wire        rate_change;
   
   setting_reg #(.my_addr(BASE+0)) sr_0
     (.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),
      .in(set_data),.out(phase_inc),.changed());

   setting_reg #(.my_addr(BASE+1), .width(18)) sr_1
     (.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),
      .in(set_data),.out(scale_factor),.changed());
   
   setting_reg #(.my_addr(BASE+2), .width(10)) sr_2
     (.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),
      .in(set_data),.out({enable_hb1, enable_hb2, interp_rate}),.changed(rate_change));

   // Strobes are all now delayed by 1 cycle for timing reasons
   wire        strobe_cic_pre, strobe_hb1_pre, strobe_hb2_pre;
   reg 	       strobe_cic = 1;
   reg 	       strobe_hb1 = 1;
   reg 	       strobe_hb2 = 1;

  assign strobe = strobe_hb1;
   
   cic_strober #(.WIDTH(8))
     cic_strober(.clock(clk),.reset(rst),.enable(run & ~rate_change),.rate(interp_rate),
		 .strobe_fast(1),.strobe_slow(strobe_cic_pre) );
   cic_strober #(.WIDTH(2))
     hb2_strober(.clock(clk),.reset(rst),.enable(run & ~rate_change),.rate(enable_hb2 ? 2 : 1),
		 .strobe_fast(strobe_cic_pre),.strobe_slow(strobe_hb2_pre) );
   cic_strober #(.WIDTH(2))
     hb1_strober(.clock(clk),.reset(rst),.enable(run & ~rate_change),.rate(enable_hb1 ? 2 : 1),
		 .strobe_fast(strobe_hb2_pre),.strobe_slow(strobe_hb1_pre) );
   
   always @(posedge clk) strobe_hb1 <= strobe_hb1_pre;
   always @(posedge clk) strobe_hb2 <= strobe_hb2_pre;
   always @(posedge clk) strobe_cic <= strobe_cic_pre;

   // NCO
   always @(posedge clk)
     if(rst)
       phase <= 0;
     else if(~run)
       phase <= 0;
     else
       phase <= phase + phase_inc;
   
   wire        signed [17:0] da, db;
   wire        signed [35:0] prod_i, prod_q;

   assign tx_fe_i = prod_i[33:34-WIDTH];
   assign tx_fe_q = prod_q[33:34-WIDTH];

   wire [17:0] i_interp, q_interp;

   wire [17:0] hb1_i, hb1_q, hb2_i, hb2_q;

   wire [7:0]  cpo = enable_hb2 ? ({interp_rate,1'b0}) : interp_rate;
   // Note that max CIC rate is 128, which would give an overflow on cpo if enable_hb2 is true,
   //   but the default case inside hb_interp handles this
   
   hb_interp #(.IWIDTH(18),.OWIDTH(18),.ACCWIDTH(WIDTH)) hb_interp_i
     (.clk(clk),.rst(rst),.bypass(~enable_hb1),.cpo(cpo),.stb_in(strobe_hb1),.data_in({sample[31:16], 2'b0}),.stb_out(strobe_hb2),.data_out(hb1_i));
   hb_interp #(.IWIDTH(18),.OWIDTH(18),.ACCWIDTH(WIDTH)) hb_interp_q
     (.clk(clk),.rst(rst),.bypass(~enable_hb1),.cpo(cpo),.stb_in(strobe_hb1),.data_in({sample[15:0], 2'b0}),.stb_out(strobe_hb2),.data_out(hb1_q));
   
   small_hb_int #(.WIDTH(18)) small_hb_interp_i
     (.clk(clk),.rst(rst),.bypass(~enable_hb2),.stb_in(strobe_hb2),.data_in(hb1_i),
      .output_rate(interp_rate),.stb_out(strobe_cic),.data_out(hb2_i));
   small_hb_int #(.WIDTH(18)) small_hb_interp_q
     (.clk(clk),.rst(rst),.bypass(~enable_hb2),.stb_in(strobe_hb2),.data_in(hb1_q),
      .output_rate(interp_rate),.stb_out(strobe_cic),.data_out(hb2_q));
   
   cic_interp  #(.bw(18),.N(4),.log2_of_max_rate(7))
     cic_interp_i(.clock(clk),.reset(rst),.enable(run & ~rate_change),.rate(interp_rate),
		  .strobe_in(strobe_cic),.strobe_out(1),
		  .signal_in(hb2_i),.signal_out(i_interp));
   
   cic_interp  #(.bw(18),.N(4),.log2_of_max_rate(7))
     cic_interp_q(.clock(clk),.reset(rst),.enable(run & ~rate_change),.rate(interp_rate),
		  .strobe_in(strobe_cic),.strobe_out(1),
		  .signal_in(hb2_q),.signal_out(q_interp));

   localparam  cwidth = WIDTH;  // was 18
   localparam  zwidth = 24;  // was 16

   wire [cwidth-1:0] da_c, db_c;
   
   cordic_z24 #(.bitwidth(cwidth))
     cordic(.clock(clk), .reset(rst), .enable(run),
	    .xi({i_interp,{(cwidth-18){1'b0}}}),.yi({q_interp,{(cwidth-18){1'b0}}}),
	    .zi(phase[31:32-zwidth]),
	    .xo(da_c),.yo(db_c),.zo() );
   
   MULT18X18S MULT18X18S_inst 
     (.P(prod_i),    // 36-bit multiplier output
      .A(da_c[cwidth-1:cwidth-18]),    // 18-bit multiplier input
      .B(scale_factor),    // 18-bit multiplier input
      .C(clk),    // Clock input
      .CE(1),  // Clock enable input
      .R(rst)     // Synchronous reset input
      );
   
   MULT18X18S MULT18X18S_inst_2 
     (.P(prod_q),    // 36-bit multiplier output
      .A(db_c[cwidth-1:cwidth-18]),    // 18-bit multiplier input
      .B(scale_factor),    // 18-bit multiplier input
      .C(clk),    // Clock input
      .CE(1),  // Clock enable input
      .R(rst)     // Synchronous reset input
      );

   assign      debug = {strobe_cic, strobe_hb1, strobe_hb2,run};

endmodule // duc_chain