Merge branch 'fpga_next' into next

19 files changed, 659 insertions, 459 deletions

diff --git a/fpga/usrp2/sdr_lib/Makefile.srcs b/fpga/usrp2/sdr_lib/Makefile.srcs
index 90eede20f..defbced17 100644
--- a/fpga/usrp2/sdr_lib/Makefile.srcs
+++ b/fpga/usrp2/sdr_lib/Makefile.srcs
@@ -8,6 +8,8 @@
 SDR_LIB_SRCS = $(abspath $(addprefix $(BASE_DIR)/../sdr_lib/, \
 acc.v \
 add2.v \
+add2_and_clip.v \
+add2_and_clip_reg.v \
 add2_and_round.v \
 add2_and_round_reg.v \
 add2_reg.v \
@@ -22,16 +24,16 @@ cordic.v \
 cordic_z24.v \
 cordic_stage.v \
 dsp_core_rx.v \
-dsp_core_rx_old.v \
 dsp_core_tx.v \
 hb_dec.v \
 hb_interp.v \
 round.v \
 round_reg.v \
-rx_control.v \
+round_sd.v \
 rx_dcoffset.v \
+rx_frontend.v \
 sign_extend.v \
 small_hb_dec.v \
 small_hb_int.v \
-tx_control.v \
+tx_frontend.v \
 ))
diff --git a/fpga/usrp2/sdr_lib/add2_and_clip.v b/fpga/usrp2/sdr_lib/add2_and_clip.v
new file mode 100644
index 000000000..663f5d004
--- /dev/null
+++ b/fpga/usrp2/sdr_lib/add2_and_clip.v
@@ -0,0 +1,12 @@
+
+module add2_and_clip
+  #(parameter WIDTH=16)
+    (input [WIDTH-1:0] in1,
+     input [WIDTH-1:0] in2,
+     output [WIDTH-1:0] sum);
+
+   wire [WIDTH:0] 	sum_int = {in1[WIDTH-1],in1} + {in2[WIDTH-1],in2};
+   clip #(.bits_in(WIDTH+1),.bits_out(WIDTH)) clip
+     (.in(sum_int),.out(sum));
+   
+endmodule // add2_and_clip
diff --git a/fpga/usrp2/sdr_lib/add2_and_clip_reg.v b/fpga/usrp2/sdr_lib/add2_and_clip_reg.v
new file mode 100644
index 000000000..8073b3b54
--- /dev/null
+++ b/fpga/usrp2/sdr_lib/add2_and_clip_reg.v
@@ -0,0 +1,25 @@
+
+module add2_and_clip_reg
+  #(parameter WIDTH=16)
+    (input clk,
+     input rst,
+     input [WIDTH-1:0] in1,
+     input [WIDTH-1:0] in2,
+     input strobe_in,
+     output reg [WIDTH-1:0] sum,
+     output reg strobe_out);
+
+   wire [WIDTH-1:0] sum_int;
+   
+   add2_and_clip #(.WIDTH(WIDTH)) add2_and_clip (.in1(in1),.in2(in2),.sum(sum_int));
+
+   always @(posedge clk)
+     if(rst)
+       sum <= 0;
+     else if(strobe_in)
+       sum <= sum_int;
+
+   always @(posedge clk)
+     strobe_out <= strobe_in;
+   
+endmodule // add2_and_clip_reg
diff --git a/fpga/usrp2/sdr_lib/dsp_core_rx.v b/fpga/usrp2/sdr_lib/dsp_core_rx.v
index 0e69e53f7..639744de7 100644
--- a/fpga/usrp2/sdr_lib/dsp_core_rx.v
+++ b/fpga/usrp2/sdr_lib/dsp_core_rx.v
@@ -21,8 +21,8 @@ module dsp_core_rx
   (input clk, input rst,
    input set_stb, input [7:0] set_addr, input [31:0] set_data,
 
-   input [13:0] adc_a, input adc_ovf_a,
-   input [13:0] adc_b, input adc_ovf_b,
+   input [23:0] adc_i, input adc_ovf_i,
+   input [23:0] adc_q, input adc_ovf_q,
    
    output [31:0] sample,
    input run,
@@ -30,70 +30,56 @@ module dsp_core_rx
    output [31:0] debug
    );
 
-   wire [15:0] scale_i, scale_q;
-   wire [13:0] adc_a_ofs, adc_b_ofs;
-   reg [13:0] adc_i, adc_q;
    wire [31:0] phase_inc;
    reg [31:0]  phase;
 
-   wire [35:0] prod_i, prod_q;
-   wire [23:0] i_cordic, q_cordic;
+   wire [24:0] i_cordic, q_cordic;
+   wire [23:0] i_cordic_clip, q_cordic_clip;
    wire [23:0] i_cic, q_cic;
-   wire [17:0] i_cic_scaled, q_cic_scaled;
-   wire [17:0] i_hb1, q_hb1;
-   wire [17:0] i_hb2, q_hb2;
-   wire [15:0] i_out, q_out;
-
+   wire [23:0] i_hb1, q_hb1;
+   wire [23:0] i_hb2, q_hb2;
+   
    wire        strobe_cic, strobe_hb1, strobe_hb2;
    wire        enable_hb1, enable_hb2;
    wire [7:0]  cic_decim_rate;
 
+   reg [23:0]  adc_i_mux, adc_q_mux;
+   wire        realmode;
+   wire        swap_iq;
+   
    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)) sr_1
      (.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),
       .in(set_data),.out({scale_i,scale_q}),.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, cic_decim_rate}),.changed());
 
-   rx_dcoffset #(.WIDTH(14),.ADDR(BASE+3)) rx_dcoffset_a
-     (.clk(clk),.rst(rst),.set_stb(set_stb),.set_addr(set_addr),.set_data(set_data),
-      .adc_in(adc_a),.adc_out(adc_a_ofs));
-   
-   rx_dcoffset #(.WIDTH(14),.ADDR(BASE+4)) rx_dcoffset_b
-     (.clk(clk),.rst(rst),.set_stb(set_stb),.set_addr(set_addr),.set_data(set_data),
-      .adc_in(adc_b),.adc_out(adc_b_ofs));
-
-   wire [7:0]  muxctrl;
-   setting_reg #(.my_addr(BASE+5), .width(8)) sr_8
-     (.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),
-      .in(set_data),.out(muxctrl),.changed());
-
-   wire [1:0] gpio_ena;
-   setting_reg #(.my_addr(BASE+6), .width(2)) sr_9
+   setting_reg #(.my_addr(BASE+3), .width(2)) sr_3
      (.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),
-      .in(set_data),.out(gpio_ena),.changed());
+      .in(set_data),.out({realmode,swap_iq}),.changed());
 
-   always @(posedge clk)
-     case(muxctrl[3:0])		// The I mapping
-       0: adc_i <= adc_a_ofs;
-       1: adc_i <= adc_b_ofs;
-       2: adc_i <= 0;
-       default: adc_i <= 0;
-     endcase // case (muxctrl[3:0])
+   // MUX so we can do realmode signals on either input
    
    always @(posedge clk)
-     case(muxctrl[7:4])		// The Q mapping
-       0: adc_q <= adc_a_ofs;
-       1: adc_q <= adc_b_ofs;
-       2: adc_q <= 0;
-       default: adc_q <= 0;
-     endcase // case (muxctrl[7:4])
-          
+     if(swap_iq)
+       begin
+	  adc_i_mux <= adc_q;
+	  adc_q_mux <= realmode ? 24'd0 : adc_i;
+       end
+     else
+       begin
+	  adc_i_mux <= adc_i;
+	  adc_q_mux <= realmode ? 24'd0 : adc_q;
+       end
+
+   // NCO
    always @(posedge clk)
      if(rst)
        phase <= 0;
@@ -102,74 +88,55 @@ module dsp_core_rx
      else
        phase <= phase + phase_inc;
 
-   MULT18X18S mult_i
-     (.P(prod_i),    // 36-bit multiplier output
-      .A({{4{adc_i[13]}},adc_i} ),    // 18-bit multiplier input
-      .B({{2{scale_i[15]}},scale_i}),    // 18-bit multiplier input
-      .C(clk),    // Clock input
-      .CE(1),  // Clock enable input
-      .R(rst)     // Synchronous reset input
-      );
-
-   MULT18X18S mult_q
-     (.P(prod_q),    // 36-bit multiplier output
-      .A({{4{adc_q[13]}},adc_q} ),    // 18-bit multiplier input
-      .B({{2{scale_q[15]}},scale_q}),    // 18-bit multiplier input
-      .C(clk),    // Clock input
-      .CE(1),  // Clock enable input
-      .R(rst)     // Synchronous reset input
-      ); 
-
-   
-   cordic_z24 #(.bitwidth(24))
+   // CORDIC  24-bit I/O
+   cordic_z24 #(.bitwidth(25))
      cordic(.clock(clk), .reset(rst), .enable(run),
-	    .xi(prod_i[23:0]),. yi(prod_q[23:0]), .zi(phase[31:8]),
+	    .xi({adc_i_mux[23],adc_i_mux}),. yi({adc_q_mux[23],adc_q_mux}), .zi(phase[31:8]),
 	    .xo(i_cordic),.yo(q_cordic),.zo() );
 
+   clip_reg #(.bits_in(25), .bits_out(24)) clip_i (.clk(clk), .in(i_cordic), .out(i_cordic_clip));
+   clip_reg #(.bits_in(25), .bits_out(24)) clip_q (.clk(clk), .in(q_cordic), .out(q_cordic_clip));
+
+   // CIC decimator  24 bit I/O
    cic_strober cic_strober(.clock(clk),.reset(rst),.enable(run),.rate(cic_decim_rate),
 			   .strobe_fast(1),.strobe_slow(strobe_cic) );
 
    cic_decim #(.bw(24))
      decim_i (.clock(clk),.reset(rst),.enable(run),
 	      .rate(cic_decim_rate),.strobe_in(1'b1),.strobe_out(strobe_cic),
-	      .signal_in(i_cordic),.signal_out(i_cic));
+	      .signal_in(i_cordic_clip),.signal_out(i_cic));
    
    cic_decim #(.bw(24))
      decim_q (.clock(clk),.reset(rst),.enable(run),
 	      .rate(cic_decim_rate),.strobe_in(1'b1),.strobe_out(strobe_cic),
-	      .signal_in(q_cordic),.signal_out(q_cic));
+	      .signal_in(q_cordic_clip),.signal_out(q_cic));
 
-   round_reg #(.bits_in(24),.bits_out(18)) round_icic (.clk(clk),.in(i_cic),.out(i_cic_scaled));
-   round_reg #(.bits_in(24),.bits_out(18)) round_qcic (.clk(clk),.in(q_cic),.out(q_cic_scaled));
-   reg 	       strobe_cic_d1;
-   always @(posedge clk) strobe_cic_d1 <= strobe_cic;
-   
-   small_hb_dec #(.WIDTH(18)) small_hb_i
+   // First (small) halfband  24 bit I/O
+   small_hb_dec #(.WIDTH(24)) small_hb_i
      (.clk(clk),.rst(rst),.bypass(~enable_hb1),.run(run),
-      .stb_in(strobe_cic_d1),.data_in(i_cic_scaled),.stb_out(strobe_hb1),.data_out(i_hb1));
+      .stb_in(strobe_cic),.data_in(i_cic),.stb_out(strobe_hb1),.data_out(i_hb1));
    
-   small_hb_dec #(.WIDTH(18)) small_hb_q
+   small_hb_dec #(.WIDTH(24)) small_hb_q
      (.clk(clk),.rst(rst),.bypass(~enable_hb1),.run(run),
-      .stb_in(strobe_cic_d1),.data_in(q_cic_scaled),.stb_out(),.data_out(q_hb1));
+      .stb_in(strobe_cic),.data_in(q_cic),.stb_out(),.data_out(q_hb1));
 
+   // Second (large) halfband  24 bit I/O
    wire [8:0]  cpi_hb = enable_hb1 ? {cic_decim_rate,1'b0} : {1'b0,cic_decim_rate};
-   hb_dec #(.IWIDTH(18), .OWIDTH(18), .CWIDTH(18), .ACCWIDTH(24)) hb_i
+   hb_dec #(.WIDTH(24)) hb_i
      (.clk(clk),.rst(rst),.bypass(~enable_hb2),.run(run),.cpi(cpi_hb),
       .stb_in(strobe_hb1),.data_in(i_hb1),.stb_out(strobe_hb2),.data_out(i_hb2));
 
-   hb_dec #(.IWIDTH(18), .OWIDTH(18), .CWIDTH(18), .ACCWIDTH(24)) hb_q
+   hb_dec #(.WIDTH(24)) hb_q
      (.clk(clk),.rst(rst),.bypass(~enable_hb2),.run(run),.cpi(cpi_hb),
       .stb_in(strobe_hb1),.data_in(q_hb1),.stb_out(),.data_out(q_hb2));
 
-   round #(.bits_in(18),.bits_out(16)) round_iout (.in(i_hb2),.out(i_out));
-   round #(.bits_in(18),.bits_out(16)) round_qout (.in(q_hb2),.out(q_out));
+   // Round final answer to 16 bits
+   round_sd #(.WIDTH_IN(24),.WIDTH_OUT(16)) round_i
+     (.clk(clk),.reset(rst), .in(i_hb2),.strobe_in(strobe_hb2), .out(sample[31:16]), .strobe_out(strobe));
 
-   reg [31:0] sample_reg;
-   always @(posedge clk)
-     sample_reg <= {i_out,q_out};
+   round_sd #(.WIDTH_IN(24),.WIDTH_OUT(16)) round_q
+     (.clk(clk),.reset(rst), .in(q_hb2),.strobe_in(strobe_hb2), .out(sample[15:0]), .strobe_out());
    
-   assign      sample = sample_reg;
-   assign      strobe = strobe_hb2;
-   assign      debug = {enable_hb1, enable_hb2, run, strobe, strobe_cic, strobe_cic_d1, strobe_hb1, strobe_hb2};
+   assign      debug = {enable_hb1, enable_hb2, run, strobe, strobe_cic, strobe_hb1, strobe_hb2};
    
 endmodule // dsp_core_rx
diff --git a/fpga/usrp2/sdr_lib/dsp_core_rx_tb.v b/fpga/usrp2/sdr_lib/dsp_core_rx_tb.v
new file mode 100644
index 000000000..271db8cef
--- /dev/null
+++ b/fpga/usrp2/sdr_lib/dsp_core_rx_tb.v
@@ -0,0 +1,73 @@
+
+`timescale 1ns/1ns
+module dsp_core_rx_tb();
+   
+   reg clk, rst;
+
+   initial rst = 1;
+   initial #1000 rst = 0;
+   initial clk = 0;
+   always #5 clk = ~clk;
+   
+   initial $dumpfile("dsp_core_rx_tb.vcd");
+   initial $dumpvars(0,dsp_core_rx_tb);
+   
+   reg signed [23:0] adc_in;
+   wire signed [15:0] adc_out_i, adc_out_q;
+
+   always @(posedge clk)
+     begin
+	$display(adc_in);
+	$display(adc_out_i);
+	$display(adc_out_q);
+     end	
+
+   reg run;
+   reg set_stb;
+   reg [7:0] set_addr;
+   reg [31:0] set_data;
+   
+   dsp_core_rx #(.BASE(0)) dsp_core_rx
+     (.clk(clk),.rst(rst),
+      .set_stb(set_stb),.set_addr(set_addr),.set_data(set_data),
+      .adc_i(adc_in), .adc_ovf_i(0),
+      .adc_q(0), .adc_ovf_q(0),
+      .sample({adc_out_i,adc_out_q}),
+      .run(run), .strobe(), .debug());
+
+   initial
+     begin
+	run <= 0;
+	@(negedge rst);
+	@(posedge clk);
+	set_addr <= 1;
+	set_data <= {16'd64,16'd64};  // set gains
+	set_stb <= 1;
+	@(posedge clk);
+	set_addr <= 2;
+	set_data <= {16'd0,8'd3,8'd1}; // set decim
+	set_stb <= 1;
+	@(posedge clk);
+	set_addr <= 0;
+	//set_data <= {32'h0000_0000};
+	set_data <= {32'h01CA_C083}; // 700 kHz
+	set_stb <= 1;
+	@(posedge clk);
+	set_stb <= 0;
+	@(posedge clk);
+	run <= 1;
+     end
+
+   always @(posedge clk)
+     //adc_in <= 24'd1000000;
+     adc_in <= 24'h80_0000;
+   
+   /*
+   always @(posedge clk)
+     if(rst)
+       adc_in <= 0;
+     else
+       adc_in <= adc_in + 4;
+   //adc_in <= (($random % 473) + 23)/4;
+*/   
+endmodule // dsp_core_rx_tb
diff --git a/fpga/usrp2/sdr_lib/dsp_core_tx.v b/fpga/usrp2/sdr_lib/dsp_core_tx.v
index 58bd82f6e..f02c63b42 100644
--- a/fpga/usrp2/sdr_lib/dsp_core_tx.v
+++ b/fpga/usrp2/sdr_lib/dsp_core_tx.v
@@ -21,8 +21,7 @@ module dsp_core_tx
   (input clk, input rst,
    input set_stb, input [7:0] set_addr, input [31:0] set_data,
 
-   output reg [15:0] dac_a,
-   output reg [15:0] dac_b,
+   output [23:0] tx_i, output [23:0] tx_q,
 
    // To tx_control
    input [31:0] sample,
@@ -50,10 +49,6 @@ module dsp_core_tx
      (.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),
       .in(set_data),.out({enable_hb1, enable_hb2, interp_rate}),.changed());
 
-   setting_reg #(.my_addr(BASE+4), .width(8)) sr_4
-     (.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),
-      .in(set_data),.out({dacmux_b,dacmux_a}),.changed());
-
    // 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;
@@ -148,20 +143,9 @@ module dsp_core_tx
       .CE(1),  // Clock enable input
       .R(rst)     // Synchronous reset input
       );
-   
-   always @(posedge clk)
-     case(dacmux_a)
-       0 : dac_a <= prod_i[28:13];
-       1 : dac_a <= prod_q[28:13];
-       default : dac_a <= 0;
-     endcase // case(dacmux_a)
-   
-   always @(posedge clk)
-     case(dacmux_b)
-       0 : dac_b <= prod_i[28:13];
-       1 : dac_b <= prod_q[28:13];
-       default : dac_b <= 0;
-     endcase // case(dacmux_b)
+
+   assign tx_i = prod_i[28:5];
+   assign tx_q = prod_q[28:5];
    
    assign      debug = {strobe_cic, strobe_hb1, strobe_hb2,run};
 
diff --git a/fpga/usrp2/sdr_lib/hb_dec.v b/fpga/usrp2/sdr_lib/hb_dec.v
index 9747f0adb..8d21c21c0 100644
--- a/fpga/usrp2/sdr_lib/hb_dec.v
+++ b/fpga/usrp2/sdr_lib/hb_dec.v
@@ -22,17 +22,27 @@
 // myfilt = round(2^18 * halfgen4(.7/4,8))
 
 module hb_dec
-  #(parameter IWIDTH=18, OWIDTH=18, CWIDTH=18, ACCWIDTH=24)
+  #(parameter WIDTH=24)
     (input clk,
      input rst,
      input bypass,
      input run,
      input [8:0] cpi,  // Clocks per input -- equal to the decimation ratio ahead of this block
      input stb_in,
-     input [IWIDTH-1:0] data_in,
+     input [WIDTH-1:0] data_in,
      output reg stb_out,
-     output reg [OWIDTH-1:0] data_out);
+     output reg [WIDTH-1:0] data_out);
 
+   localparam INTWIDTH = 17;
+   localparam ACCWIDTH = WIDTH + 3;
+   
+   // Round off inputs to 17 bits because of 18 bit multipliers
+   wire [INTWIDTH-1:0] 	     data_rnd;
+   wire 		     stb_rnd;
+   
+   round_sd #(.WIDTH_IN(WIDTH),.WIDTH_OUT(INTWIDTH)) round_in
+     (.clk(clk),.reset(rst),.in(data_in),.strobe_in(stb_in),.out(data_rnd),.strobe_out(stb_rnd));
+   
    // Control
    reg [3:0] 		addr_odd_a, addr_odd_b, addr_odd_c, addr_odd_d;
    wire 		write_odd, write_even, do_mult;
@@ -45,16 +55,16 @@ module hb_dec
    always @(posedge clk)
      if(rst | ~run)
        odd <= 0;
-     else if(stb_in)
+     else if(stb_rnd)
        odd <= ~odd;
 
-   assign 		write_odd = stb_in & odd;
-   assign 		write_even = stb_in & ~odd;
+   assign 		write_odd = stb_rnd & odd;
+   assign 		write_even = stb_rnd & ~odd;
 
    always @(posedge clk)
      if(rst | ~run)
        phase <= 0;
-     else if(stb_in & odd)
+     else if(stb_rnd & odd)
        phase <= 1;
      else if(phase == 4)
        phase <= 0;
@@ -69,7 +79,7 @@ module hb_dec
      if(rst)
        stb_out_pre <= 0;
      else
-       stb_out_pre <= {stb_out_pre[14:0],(stb_in & odd)};
+       stb_out_pre <= {stb_out_pre[14:0],(stb_rnd & odd)};
 
    always @*
      case(phase)
@@ -93,11 +103,12 @@ module hb_dec
    assign clear = stb_out_pre[3];
    
    // Data
-   wire [IWIDTH-1:0] data_odd_a, data_odd_b, data_odd_c, data_odd_d;
-   wire [IWIDTH-1:0] sum1, sum2;	
-   wire [OWIDTH-1:0] final_sum;
-   reg [CWIDTH-1:0]  coeff1, coeff2;
-   wire [35:0] 	     prod1, prod2;
+   wire [INTWIDTH-1:0] data_odd_a, data_odd_b, data_odd_c, data_odd_d;
+   reg [INTWIDTH:0]    sum1, sum2;    // these are 18-bit inputs to mult
+   reg [WIDTH:0]       final_sum;
+   wire [WIDTH-1:0]    final_sum_clip;
+   reg [17:0] 	       coeff1, coeff2;
+   wire [35:0] 	       prod1, prod2;
 
    always @*            // Outer coeffs
      case(phase_d1)
@@ -117,19 +128,19 @@ module hb_dec
        default : coeff2 = -6107;
      endcase // case(phase)
    
-   srl #(.WIDTH(IWIDTH)) srl_odd_a
-     (.clk(clk),.write(write_odd),.in(data_in),.addr(addr_odd_a),.out(data_odd_a));
-   srl #(.WIDTH(IWIDTH)) srl_odd_b
-     (.clk(clk),.write(write_odd),.in(data_in),.addr(addr_odd_b),.out(data_odd_b));
-   srl #(.WIDTH(IWIDTH)) srl_odd_c
-     (.clk(clk),.write(write_odd),.in(data_in),.addr(addr_odd_c),.out(data_odd_c));
-   srl #(.WIDTH(IWIDTH)) srl_odd_d
-     (.clk(clk),.write(write_odd),.in(data_in),.addr(addr_odd_d),.out(data_odd_d));
-
-   add2_reg /*_and_round_reg*/ #(.WIDTH(IWIDTH)) add1 (.clk(clk),.in1(data_odd_a),.in2(data_odd_b),.sum(sum1));
-   add2_reg /*_and_round_reg*/ #(.WIDTH(IWIDTH)) add2 (.clk(clk),.in1(data_odd_c),.in2(data_odd_d),.sum(sum2));
-
-   wire [IWIDTH-1:0] data_even;
+   srl #(.WIDTH(INTWIDTH)) srl_odd_a
+     (.clk(clk),.write(write_odd),.in(data_rnd),.addr(addr_odd_a),.out(data_odd_a));
+   srl #(.WIDTH(INTWIDTH)) srl_odd_b
+     (.clk(clk),.write(write_odd),.in(data_rnd),.addr(addr_odd_b),.out(data_odd_b));
+   srl #(.WIDTH(INTWIDTH)) srl_odd_c
+     (.clk(clk),.write(write_odd),.in(data_rnd),.addr(addr_odd_c),.out(data_odd_c));
+   srl #(.WIDTH(INTWIDTH)) srl_odd_d
+     (.clk(clk),.write(write_odd),.in(data_rnd),.addr(addr_odd_d),.out(data_odd_d));
+
+   always @(posedge clk) sum1 <= {data_odd_a[INTWIDTH-1],data_odd_a} + {data_odd_b[INTWIDTH-1],data_odd_b};
+   always @(posedge clk) sum2 <= {data_odd_c[INTWIDTH-1],data_odd_c} + {data_odd_d[INTWIDTH-1],data_odd_d};
+   
+   wire [INTWIDTH-1:0] data_even;
    reg [3:0] 	     addr_even;
 
    always @(posedge clk)
@@ -140,49 +151,39 @@ module hb_dec
        default : addr_even <= 7;
      endcase // case(cpi)
    
-   srl #(.WIDTH(IWIDTH)) srl_even
-     (.clk(clk),.write(write_even),.in(data_in),.addr(addr_even),.out(data_even));
-
-   localparam 		MWIDTH = ACCWIDTH-2;   
-   wire [MWIDTH-1:0] 	sum_of_prod;
+   srl #(.WIDTH(INTWIDTH)) srl_even
+     (.clk(clk),.write(write_even),.in(data_rnd),.addr(addr_even),.out(data_even));
 
    MULT18X18S mult1(.C(clk), .CE(do_mult), .R(rst), .P(prod1), .A(coeff1), .B(sum1) );
    MULT18X18S mult2(.C(clk), .CE(do_mult), .R(rst), .P(prod2), .A(coeff2), .B(sum2) );
-   add2_and_round_reg #(.WIDTH(MWIDTH)) 
-     add3 (.clk(clk),.in1(prod1[35:36-MWIDTH]),.in2(prod2[35:36-MWIDTH]),.sum(sum_of_prod));
 
-   wire [ACCWIDTH-1:0] 	acc_out;
+   reg [35:0] 	     sum_of_prod;
+   always @(posedge clk) sum_of_prod <= prod1 + prod2;   // Can't overflow
    
-   acc #(.IWIDTH(MWIDTH),.OWIDTH(ACCWIDTH)) 
-     acc (.clk(clk),.clear(clear),.acc(do_acc),.in(sum_of_prod),.out(acc_out));
+   wire [ACCWIDTH-1:0] 	acc_out;
+   acc #(.IWIDTH(ACCWIDTH-2),.OWIDTH(ACCWIDTH))
+     acc (.clk(clk),.clear(clear),.acc(do_acc),.in(sum_of_prod[35:38-ACCWIDTH]),.out(acc_out));
 
-   localparam 		SHIFT_FACTOR = ACCWIDTH-IWIDTH-5;
    wire [ACCWIDTH-1:0] 	data_even_signext;
-   wire [ACCWIDTH:0] 	final_sum_unrounded;
 
-   sign_extend #(.bits_in(IWIDTH),.bits_out(ACCWIDTH-SHIFT_FACTOR))
-     signext_data_even (.in(data_even),.out(data_even_signext[ACCWIDTH-1:SHIFT_FACTOR]));
-   assign 		data_even_signext[SHIFT_FACTOR-1:0] = 0;
+   localparam SHIFT_FACTOR = 6;
    
-   add2_reg /* add2_and_round_reg */ #(.WIDTH(ACCWIDTH+1)) 
-     final_adder (.clk(clk), .in1({acc_out,1'b0}), .in2({data_even_signext,1'b0}), .sum(final_sum_unrounded));
-
-   round_reg #(.bits_in(ACCWIDTH-4),.bits_out(OWIDTH))
-     final_round (.clk(clk),.in(final_sum_unrounded[ACCWIDTH-5:0]),.out(final_sum));
-
-   // Output
-   always @(posedge clk)
-     if(bypass)
-       data_out <= data_in;
-     else if(stb_out_pre[9])
-       data_out <= final_sum;
+   sign_extend #(.bits_in(INTWIDTH),.bits_out(ACCWIDTH-SHIFT_FACTOR)) signext_data_even 
+     (.in(data_even),.out(data_even_signext[ACCWIDTH-1:SHIFT_FACTOR]));
+   assign 		data_even_signext[SHIFT_FACTOR-1:0] = 0;
 
+   always @(posedge clk) final_sum <= acc_out + data_even_signext;
+   
+   clip #(.bits_in(WIDTH+1), .bits_out(WIDTH)) clip (.in(final_sum), .out(final_sum_clip));
+   
+   // Output MUX to allow for bypass
+   wire 		selected_stb = bypass ? stb_in : stb_out_pre[8];
+   
    always @(posedge clk)
-     if(rst)
-       stb_out <= 0;
-     else if(bypass)
-       stb_out <= stb_in;
-     else
-       stb_out <= stb_out_pre[9];
- 
+     begin
+	stb_out  <= selected_stb;
+	if(selected_stb)
+	  data_out <= bypass ? data_in : final_sum_clip;
+     end
+   
 endmodule // hb_dec
diff --git a/fpga/usrp2/sdr_lib/hb_dec_tb.v b/fpga/usrp2/sdr_lib/hb_dec_tb.v
index 256f6085d..153cfba76 100644
--- a/fpga/usrp2/sdr_lib/hb_dec_tb.v
+++ b/fpga/usrp2/sdr_lib/hb_dec_tb.v
@@ -18,7 +18,7 @@
 module hb_dec_tb( ) ;
    
     // Parameters for instantiation
-    parameter               clocks  = 9'd2 ; // Number of clocks per input
+    parameter               clocks  = 9'd12 ; // Number of clocks per input
     parameter               decim   = 1 ; // Sets the filter to decimate
     parameter               rate    = 2 ; // Sets the decimation rate
 
@@ -26,9 +26,9 @@ module hb_dec_tb( ) ;
     reg                     reset ;
     reg                     enable ;
     reg                     strobe_in ;
-    reg     signed  [17:0]  data_in ;
+    reg     signed  [23:0]  data_in ;
     wire                    strobe_out ;
-    wire    signed  [17:0]  data_out ;
+    wire    signed  [23:0]  data_out ;
 
    initial
      begin
@@ -65,8 +65,8 @@ module hb_dec_tb( ) ;
     */
 
    
-   hb_dec #(.IWIDTH(18),.OWIDTH(18),.CWIDTH(18),.ACCWIDTH(24)) uut
-     (.clk(clock),.rst(reset),.bypass(0),.cpi(clocks),.stb_in(strobe_in),.data_in(data_in),
+   hb_dec #(.WIDTH(24)) uut
+     (.clk(clock),.rst(reset),.bypass(0),.run(1),.cpi(clocks),.stb_in(strobe_in),.data_in(data_in),
       .stb_out(strobe_out),.data_out(data_out) );
    
     integer i, ri, ro, infile, outfile ;
diff --git a/fpga/usrp2/sdr_lib/input.dat b/fpga/usrp2/sdr_lib/input.dat
index 1e649ac2e..85b5887e8 100644
--- a/fpga/usrp2/sdr_lib/input.dat
+++ b/fpga/usrp2/sdr_lib/input.dat
@@ -6,7 +6,6 @@
 0
 0
 0
--131072
 0
 0
 0
@@ -16,6 +15,7 @@
 0
 0
 0
+8388607
 0
 0
 0
@@ -38,34 +38,6 @@
 0
 0
 0
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
 0
 0
 0
@@ -82,6 +54,7 @@
 0
 0
 0
+8388607
 0
 0
 0
@@ -96,200 +69,6 @@
 0
 0
 0
-131071
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-131071
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-100000
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
--131072
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
-0
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
--131072
-0
-0
 0
 0
 0
@@ -313,6 +92,56 @@
 0
 0
 0
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
+8388607
 0
 0
 0
@@ -339,3 +168,4 @@
 0
 0
 0
+
diff --git a/fpga/usrp2/sdr_lib/round.v b/fpga/usrp2/sdr_lib/round.v
index c4f9ec9cd..7a137d702 100644
--- a/fpga/usrp2/sdr_lib/round.v
+++ b/fpga/usrp2/sdr_lib/round.v
@@ -26,8 +26,10 @@ module round
   #(parameter bits_in=0,
     parameter bits_out=0)
     (input [bits_in-1:0] in,
-     output [bits_out-1:0] out);
+     output [bits_out-1:0] out,
+     output [bits_in-bits_out:0] err);
 
    assign out = in[bits_in-1:bits_in-bits_out] + (in[bits_in-1] & |in[bits_in-bits_out-1:0]);
+   assign err = in - {out,{(bits_in-bits_out){1'b0}}};
    
 endmodule // round
diff --git a/fpga/usrp2/sdr_lib/round_reg.v b/fpga/usrp2/sdr_lib/round_reg.v
index aa0972dab..6f2e974d7 100644
--- a/fpga/usrp2/sdr_lib/round_reg.v
+++ b/fpga/usrp2/sdr_lib/round_reg.v
@@ -27,13 +27,18 @@ module round_reg
     parameter bits_out=0)
     (input clk,
      input [bits_in-1:0] in,
-     output reg [bits_out-1:0] out);
+     output reg [bits_out-1:0] out,
+     output reg [bits_in-bits_out:0] err);
 
    wire [bits_out-1:0] temp;
-
-   round #(.bits_in(bits_in),.bits_out(bits_out)) round (.in(in),.out(temp));
+   wire [bits_in-bits_out:0] err_temp;
+   
+   round #(.bits_in(bits_in),.bits_out(bits_out)) round (.in(in),.out(temp), .err(err_temp));
    
    always @(posedge clk)
      out <= temp;
+
+   always @(posedge clk)
+     err <= err_temp;
    
-endmodule // round
+endmodule // round_reg
diff --git a/fpga/usrp2/sdr_lib/round_sd.v b/fpga/usrp2/sdr_lib/round_sd.v
new file mode 100644
index 000000000..aeeb3502f
--- /dev/null
+++ b/fpga/usrp2/sdr_lib/round_sd.v
@@ -0,0 +1,22 @@
+
+
+module round_sd
+  #(parameter WIDTH_IN=18,
+    parameter WIDTH_OUT=16)
+   (input clk, input reset,
+    input [WIDTH_IN-1:0] in, input strobe_in,
+    output [WIDTH_OUT-1:0] out, output strobe_out);
+
+   localparam ERR_WIDTH = WIDTH_IN - WIDTH_OUT + 1;
+
+   wire [ERR_WIDTH-1:0]  err;
+   wire [WIDTH_IN-1:0] 	 err_ext, sum;
+  
+   sign_extend #(.bits_in(ERR_WIDTH),.bits_out(WIDTH_IN)) ext_err (.in(err), .out(err_ext));
+   
+   add2_and_clip_reg #(.WIDTH(WIDTH_IN)) add2_and_clip_reg
+     (.clk(clk), .rst(reset), .in1(in), .in2(err_ext), .strobe_in(strobe_in), .sum(sum), .strobe_out(strobe_out));
+   
+   round #(.bits_in(WIDTH_IN),.bits_out(WIDTH_OUT)) round_sum (.in(sum), .out(out), .err(err));
+   
+endmodule // round_sd
diff --git a/fpga/usrp2/sdr_lib/round_sd_tb.v b/fpga/usrp2/sdr_lib/round_sd_tb.v
new file mode 100644
index 000000000..1e8e9a323
--- /dev/null
+++ b/fpga/usrp2/sdr_lib/round_sd_tb.v
@@ -0,0 +1,58 @@
+
+module round_sd_tb();
+   
+   reg clk, rst;
+
+   initial rst = 1;
+   initial #1000 rst = 0;
+   initial clk = 0;
+   always #5 clk = ~clk;
+   
+   initial $dumpfile("round_sd_tb.vcd");
+   initial $dumpvars(0,round_sd_tb);
+
+   localparam WIDTH_IN = 8;
+   localparam WIDTH_OUT = 5;
+   
+   reg [WIDTH_IN-1:0] adc_in, adc_in_del;
+   wire [WIDTH_OUT-1:0] adc_out;
+
+   integer 		factor = 1<<(WIDTH_IN-WIDTH_OUT);
+   
+   always @(posedge clk)
+     if(~rst)
+	begin  
+	   if(adc_in_del[WIDTH_IN-1])
+	     $write("-%d\t",-adc_in_del);
+	   else
+	     $write("%d\t",adc_in_del);
+	   if(adc_out[WIDTH_OUT-1])
+	     $write("-%d\t",-adc_out);
+	   else
+	     $write("%d\t",adc_out);
+	   $write("\n");
+	   
+	   //$write("%f\t",adc_in_del/factor);
+	   //$write("%f\n",adc_in_del/factor-adc_out);
+	end	
+   
+   round_sd #(.WIDTH_IN(WIDTH_IN),.WIDTH_OUT(WIDTH_OUT)) 
+   round_sd(.clk(clk),.reset(rst), .in(adc_in), .strobe_in(1'b1), .out(adc_out), .strobe_out());
+
+   reg [5:0] counter = 0;
+   
+   always @(posedge clk)
+     counter <= counter+1;
+   
+   always @(posedge clk)
+     adc_in_del <= adc_in;
+
+   always @(posedge clk)
+     if(rst)
+       adc_in <= 0;
+     else if(counter == 63)
+       adc_in <= adc_in + 1;
+   
+   initial #300000 $finish;
+   
+endmodule // longfifo_tb
diff --git a/fpga/usrp2/sdr_lib/rx_dcoffset.v b/fpga/usrp2/sdr_lib/rx_dcoffset.v
index 64ff4110d..e43461261 100644
--- a/fpga/usrp2/sdr_lib/rx_dcoffset.v
+++ b/fpga/usrp2/sdr_lib/rx_dcoffset.v
@@ -18,43 +18,40 @@
 
 
 module rx_dcoffset 
-  #(parameter WIDTH=14,
-    parameter ADDR=8'd0)
-    (input clk, input rst, 
-     input set_stb, input [7:0] set_addr, input [31:0] set_data,
-     input signed [WIDTH-1:0] adc_in, output signed [WIDTH-1:0] adc_out);
-
-   // Because of some extra delays to make timing easier, the transfer function is:
-   //     (z-1)/(z^2-z-alpha)  where alpha is 1/2^n
+  #(parameter WIDTH=16,
+    parameter ADDR=8'd0,
+    parameter alpha_shift=16)
+   (input clk, input rst, 
+    input set_stb, input [7:0] set_addr, input [31:0] set_data,
+    input [WIDTH-1:0] in, output [WIDTH-1:0] out);
    
-   wire 	       set_now = set_stb & (ADDR == set_addr);
+   wire 	      set_now = set_stb & (ADDR == set_addr);
    
-   reg 		       fixed;  // uses fixed offset
-   wire 	       signed [WIDTH-1:0] fixed_dco;
-   reg 		       signed [31:0] integrator;
+   reg 		      fixed;  // uses fixed offset
+   wire [WIDTH-1:0]   fixed_dco;
+
+   localparam int_width = WIDTH + alpha_shift;
+   reg [int_width-1:0] integrator;
+   wire [WIDTH-1:0]    quantized;
 
    always @(posedge clk)
      if(rst)
        begin
 	  fixed <= 0;
-	  integrator <= 32'd0;
+	  integrator <= {int_width{1'b0}};
        end
      else if(set_now)
        begin
-	  integrator <= {set_data[WIDTH-1:0],{(32-WIDTH){1'b0}}};
+	  //integrator <= {set_data[30:0],{(31-int_width){1'b0}}};
 	  fixed <= set_data[31];
        end
      else if(~fixed)
-       integrator <= integrator + adc_out;
-   
-   wire [WIDTH:0] scaled_integrator;
-   
-   round #(.bits_in(33),.bits_out(15)) round (.in({integrator[31],integrator}),.out(scaled_integrator));
-   
-   wire [WIDTH:0]      adc_out_int = {adc_in[WIDTH-1],adc_in} - scaled_integrator;
+       integrator <= integrator +  {{(alpha_shift){out[WIDTH-1]}},out};
 
-   clip_reg #(.bits_in(WIDTH+1),.bits_out(WIDTH)) clip_adc
-     (.clk(clk),.in(adc_out_int),.out(adc_out));
+   round_sd #(.WIDTH_IN(int_width),.WIDTH_OUT(WIDTH)) round_sd
+     (.clk(clk), .reset(rst), .in(integrator), .strobe_in(1'b1), .out(quantized), .strobe_out());
    
+   add2_and_clip_reg #(.WIDTH(WIDTH)) add2_and_clip_reg
+     (.clk(clk), .rst(rst), .in1(in), .in2(-quantized), .strobe_in(1'b1), .sum(out), .strobe_out());
 
 endmodule // rx_dcoffset
diff --git a/fpga/usrp2/sdr_lib/rx_dcoffset_tb.v b/fpga/usrp2/sdr_lib/rx_dcoffset_tb.v
index b0dd8cb05..b4fb66ad7 100644
--- a/fpga/usrp2/sdr_lib/rx_dcoffset_tb.v
+++ b/fpga/usrp2/sdr_lib/rx_dcoffset_tb.v
@@ -29,14 +29,26 @@ module rx_dcoffset_tb();
    initial $dumpfile("rx_dcoffset_tb.vcd");
    initial $dumpvars(0,rx_dcoffset_tb);
 
-   reg [13:0] adc_in = 7;
+   reg [13:0] adc_in;
    wire [13:0] adc_out;
 
    always @(posedge clk)
-     $display("%d\t%d",adc_in,adc_out);
+     begin
+	if(adc_in[13])
+	  $write("-%d,",-adc_in);
+	else
+	  $write("%d,",adc_in);
+	if(adc_out[13])
+	  $write("-%d\n",-adc_out);
+	else
+	  $write("%d\n",adc_out);
+     end	
    
-   rx_dcoffset #(.WIDTH(14),.ADDR(0))
+   rx_dcoffset #(.WIDTH(14),.ADDR(0), .alpha_shift(8))
      rx_dcoffset(.clk(clk),.rst(rst),.set_stb(0),.set_addr(0),.set_data(0),
-		 .adc_in(adc_in),.adc_out(adc_out));
+		 .in(adc_in),.out(adc_out));
+
+   always @(posedge clk)
+     adc_in <= (($random % 473) + 23)/4;
    
 endmodule // longfifo_tb
diff --git a/fpga/usrp2/sdr_lib/rx_frontend.v b/fpga/usrp2/sdr_lib/rx_frontend.v
new file mode 100644
index 000000000..04b14787e
--- /dev/null
+++ b/fpga/usrp2/sdr_lib/rx_frontend.v
@@ -0,0 +1,73 @@
+
+module rx_frontend
+  #(parameter BASE = 0)
+   (input clk, input rst,
+    input set_stb, input [7:0] set_addr, input [31:0] set_data,
+
+    input [15:0] adc_a, input adc_ovf_a,
+    input [15:0] adc_b, input adc_ovf_b,
+
+    output [23:0] i_out, output [23:0] q_out,
+    input run,
+    output [31:0] debug
+    );
+   
+   reg [15:0] 	  adc_i, adc_q;
+   wire [17:0] 	  adc_i_ofs, adc_q_ofs;
+   wire [35:0] 	  corr_i, corr_q; wire [17:0] 	  mag_corr,phase_corr;
+   wire 	  swap_iq;
+   wire [23:0] 	  i_final, q_final;
+   
+   setting_reg #(.my_addr(BASE), .width(1)) sr_8
+     (.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),
+      .in(set_data),.out(swap_iq),.changed());
+
+   always @(posedge clk)
+     if(swap_iq) // Swap
+       {adc_i,adc_q} <= {adc_b,adc_a};
+     else
+       {adc_i,adc_q} <= {adc_a,adc_b};
+       
+   setting_reg #(.my_addr(BASE+1),.width(18)) sr_1
+     (.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),
+      .in(set_data),.out(mag_corr),.changed());
+   
+   setting_reg #(.my_addr(BASE+2),.width(18)) sr_2
+     (.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),
+      .in(set_data),.out(phase_corr),.changed());
+   
+   rx_dcoffset #(.WIDTH(18),.ADDR(BASE+3)) rx_dcoffset_i
+     (.clk(clk),.rst(rst),.set_stb(set_stb),.set_addr(set_addr),.set_data(set_data),
+      .in({adc_i,2'b00}),.out(adc_i_ofs));
+   
+   rx_dcoffset #(.WIDTH(18),.ADDR(BASE+4)) rx_dcoffset_q
+     (.clk(clk),.rst(rst),.set_stb(set_stb),.set_addr(set_addr),.set_data(set_data),
+      .in({adc_q,2'b00}),.out(adc_q_ofs));
+   
+   MULT18X18S mult_mag_corr
+     (.P(corr_i), .A(adc_i_ofs), .B(mag_corr), .C(clk), .CE(1), .R(rst) ); 
+
+   MULT18X18S mult_phase_corr
+     (.P(corr_q), .A(adc_i_ofs), .B(phase_corr), .C(clk), .CE(1), .R(rst) );
+   
+   add2_and_clip_reg #(.WIDTH(24)) add_clip_i
+     (.clk(clk), .rst(rst), 
+      .in1({adc_i_ofs,6'd0}), .in2({{4{corr_i[35]}},corr_i[35:16]}), .strobe_in(1'b1), 
+      .sum(i_final), .strobe_out());
+   
+   add2_and_clip_reg #(.WIDTH(24)) add_clip_q
+     (.clk(clk), .rst(rst), 
+      .in1({adc_q_ofs,6'd0}), .in2({{4{corr_q[35]}},corr_q[35:16]}), .strobe_in(1'b1),
+      .sum(q_final), .strobe_out());
+
+   assign i_out = i_final;
+   assign q_out = q_final;
+   
+   /*
+   round_sd #(.WIDTH_IN(24),.WIDTH_OUT(18)) round_i
+     (.clk(clk), .reset(rst), .in(i_final), .strobe_in(1'b1), .out(i_out), .strobe_out());
+   
+   round_sd #(.WIDTH_IN(24),.WIDTH_OUT(18)) round_q
+     (.clk(clk), .reset(rst), .in(q_final), .strobe_in(1'b1), .out(q_out), .strobe_out());
+   */
+endmodule // rx_frontend
diff --git a/fpga/usrp2/sdr_lib/rx_frontend_tb.v b/fpga/usrp2/sdr_lib/rx_frontend_tb.v
new file mode 100644
index 000000000..487b72687
--- /dev/null
+++ b/fpga/usrp2/sdr_lib/rx_frontend_tb.v
@@ -0,0 +1,45 @@
+
+`timescale 1ns/1ns
+module rx_frontend_tb();
+   
+   reg clk, rst;
+
+   initial rst = 1;
+   initial #1000 rst = 0;
+   initial clk = 0;
+   always #5 clk = ~clk;
+   
+   initial $dumpfile("rx_frontend_tb.vcd");
+   initial $dumpvars(0,rx_frontend_tb);
+
+   reg [15:0] adc_in;
+   wire [17:0] adc_out;
+
+   always @(posedge clk)
+     begin
+	if(adc_in[13])
+	  $write("-%d,",-adc_in);
+	else
+	  $write("%d,",adc_in);
+	if(adc_out[13])
+	  $write("-%d\n",-adc_out);
+	else
+	  $write("%d\n",adc_out);
+     end	
+   
+   rx_frontend #(.BASE(0)) rx_frontend
+     (.clk(clk),.rst(rst),
+      .set_stb(0),.set_addr(0),.set_data(0),
+      .adc_a(adc_in), .adc_ovf_a(0),
+      .adc_b(0), .adc_ovf_b(0),
+      .i_out(adc_out),.q_out(),
+      .run(), .debug());
+
+   always @(posedge clk)
+     if(rst)
+       adc_in <= 0;
+     else
+       adc_in <= adc_in + 4;
+   //adc_in <= (($random % 473) + 23)/4;
+   
+endmodule // rx_frontend_tb
diff --git a/fpga/usrp2/sdr_lib/small_hb_dec.v b/fpga/usrp2/sdr_lib/small_hb_dec.v
index 151b8c287..a7f93e056 100644
--- a/fpga/usrp2/sdr_lib/small_hb_dec.v
+++ b/fpga/usrp2/sdr_lib/small_hb_dec.v
@@ -29,21 +29,30 @@ module small_hb_dec
      input stb_in,
      input [WIDTH-1:0] data_in,
      output reg stb_out,
-     output [WIDTH-1:0] data_out);
+     output reg [WIDTH-1:0] data_out);
 
-   reg 			stb_in_d1;
-   reg [WIDTH-1:0] 	data_in_d1;
-   always @(posedge clk) stb_in_d1 <= stb_in;
-   always @(posedge clk) data_in_d1 <= data_in;
+   // Round off inputs to 17 bits because of 18 bit multipliers
+   localparam INTWIDTH = 17;
+   wire [INTWIDTH-1:0] 	data_rnd;
+   wire 		stb_rnd;
+   
+   round_sd #(.WIDTH_IN(WIDTH),.WIDTH_OUT(INTWIDTH)) round_in
+     (.clk(clk),.reset(rst),.in(data_in),.strobe_in(stb_in),.out(data_rnd),.strobe_out(stb_rnd));
+   	
+   
+   reg 			stb_rnd_d1;
+   reg [INTWIDTH-1:0] 	data_rnd_d1;
+   always @(posedge clk) stb_rnd_d1 <= stb_rnd;
+   always @(posedge clk) data_rnd_d1 <= data_rnd;
    
    wire 		go;
    reg 			phase, go_d1, go_d2, go_d3, go_d4;
    always @(posedge clk)
      if(rst | ~run)
        phase <= 0;
-     else if(stb_in_d1)
+     else if(stb_rnd_d1)
        phase <= ~phase;
-   assign 		go = stb_in_d1 & phase;
+   assign 		go = stb_rnd_d1 & phase;
    always @(posedge clk) 
      if(rst | ~run)
        begin
@@ -63,11 +72,11 @@ module small_hb_dec
    wire [17:0] 		coeff_a = -10690;
    wire [17:0] 		coeff_b = 75809;
    
-   reg [WIDTH-1:0] 	d1, d2, d3, d4 , d5, d6;
+   reg [INTWIDTH-1:0] 	d1, d2, d3, d4 , d5, d6;
    always @(posedge clk)
-     if(stb_in_d1 | rst)
+     if(stb_rnd_d1 | rst)
        begin
-	  d1 <= data_in_d1;
+	  d1 <= data_rnd_d1;
 	  d2 <= d1;
 	  d3 <= d2;
 	  d4 <= d3;
@@ -76,16 +85,14 @@ module small_hb_dec
        end
 
    reg [17:0] sum_a, sum_b, middle, middle_d1;
-   wire [17:0] sum_a_unreg, sum_b_unreg;
-   add2 #(.WIDTH(18)) add2_a (.in1(data_in_d1),.in2(d6),.sum(sum_a_unreg));
-   add2 #(.WIDTH(18)) add2_b (.in1(d2),.in2(d4),.sum(sum_b_unreg));
-   
+
    always @(posedge clk)
      if(go)
        begin
-	  sum_a <= sum_a_unreg;
-	  sum_b <= sum_b_unreg;
-	  middle <= d3;
+	  sum_a <= {data_rnd_d1[INTWIDTH-1],data_rnd_d1} + {d6[INTWIDTH-1],d6};
+	  sum_b <= {d2[INTWIDTH-1],d2} + {d4[INTWIDTH-1],d4};
+	  //middle <= {d3[INTWIDTH-1],d3};
+	  middle <= {d3,1'b0};
        end
 
    always @(posedge clk)
@@ -106,23 +113,22 @@ module small_hb_dec
      else if(go_d3)
        accum <= accum + {prod};
    
-   wire [17:0] 	 accum_rnd;
-   round #(.bits_in(36),.bits_out(18)) round_acc (.in(accum),.out(accum_rnd));
+   wire [WIDTH:0] 	 accum_rnd;
+   wire [WIDTH-1:0] 	 accum_rnd_clip;
+   
+   wire 	 stb_round;
+   
+   round_sd #(.WIDTH_IN(36),.WIDTH_OUT(WIDTH+1)) round_acc 
+     (.clk(clk), .reset(rst), .in(accum), .strobe_in(go_d4), .out(accum_rnd), .strobe_out(stb_round));
 
-   reg [17:0] 	 final_sum;
+   clip #(.bits_in(WIDTH+1),.bits_out(WIDTH)) clip (.in(accum_rnd), .out(accum_rnd_clip));
+   
+   // Output
    always @(posedge clk)
-     if(bypass)
-       final_sum <= data_in_d1;
-     else if(go_d4)
-       final_sum <= accum_rnd;
+     begin
+	stb_out  <= bypass ? stb_in : stb_round;
+	data_out <= bypass ? data_in : accum_rnd_clip;
+     end
 
-   assign 	 data_out = final_sum;
 
-   always @(posedge clk)
-     if(rst)
-       stb_out <= 0;
-     else if(bypass)
-       stb_out <= stb_in_d1;
-     else
-       stb_out <= go_d4;
 endmodule // small_hb_dec
diff --git a/fpga/usrp2/sdr_lib/tx_frontend.v b/fpga/usrp2/sdr_lib/tx_frontend.v
new file mode 100644
index 000000000..d8525dd25
--- /dev/null
+++ b/fpga/usrp2/sdr_lib/tx_frontend.v
@@ -0,0 +1,86 @@
+
+module tx_frontend
+  #(parameter BASE=0,
+    parameter WIDTH_OUT=16)
+   (input clk, input rst,
+    input set_stb, input [7:0] set_addr, input [31:0] set_data,
+    input [23:0] tx_i, input [23:0] tx_q, input run,
+    output reg [WIDTH_OUT-1:0] dac_a, output reg [WIDTH_OUT-1:0] dac_b
+    );
+
+   // IQ balance --> DC offset --> rounding --> mux
+
+   wire [23:0] i_dco, q_dco, i_ofs, q_ofs;
+   wire [WIDTH_OUT-1:0] i_final, q_final;
+   wire [7:0]  mux_ctrl;
+   wire [35:0] corr_i, corr_q;
+   wire [23:0] i_bal, q_bal;
+   wire [17:0] mag_corr, phase_corr;
+   
+   setting_reg #(.my_addr(BASE+0), .width(24)) sr_0
+     (.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),
+      .in(set_data),.out(i_dco),.changed());
+
+   setting_reg #(.my_addr(BASE+1), .width(24)) sr_1
+     (.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),
+      .in(set_data),.out(q_dco),.changed());
+
+   setting_reg #(.my_addr(BASE+2),.width(18)) sr_2
+     (.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),
+      .in(set_data),.out(mag_corr),.changed());
+   
+   setting_reg #(.my_addr(BASE+3),.width(18)) sr_3
+     (.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),
+      .in(set_data),.out(phase_corr),.changed());
+  
+   setting_reg #(.my_addr(BASE+4), .width(8)) sr_4
+     (.clk(clk),.rst(rst),.strobe(set_stb),.addr(set_addr),
+      .in(set_data),.out(mux_ctrl),.changed());
+
+   // IQ Balance
+   MULT18X18S mult_mag_corr
+     (.P(corr_i), .A(tx_i[23:6]), .B(mag_corr), .C(clk), .CE(1), .R(rst) ); 
+   
+   MULT18X18S mult_phase_corr
+     (.P(corr_q), .A(tx_i[23:6]), .B(phase_corr), .C(clk), .CE(1), .R(rst) );
+   
+   add2_and_clip_reg #(.WIDTH(24)) add_clip_i
+     (.clk(clk), .rst(rst), 
+      .in1(tx_i), .in2({{4{corr_i[35]}},corr_i[35:16]}), .strobe_in(1'b1), 
+      .sum(i_bal), .strobe_out());
+   
+   add2_and_clip_reg #(.WIDTH(24)) add_clip_q
+     (.clk(clk), .rst(rst), 
+      .in1(tx_q), .in2({{4{corr_q[35]}},corr_q[35:16]}), .strobe_in(1'b1),
+      .sum(q_bal), .strobe_out());
+
+   // DC Offset
+   add2_and_clip_reg #(.WIDTH(24)) add_dco_i
+     (.clk(clk), .rst(rst), .in1(i_dco), .in2(i_bal), .strobe_in(1'b1), .sum(i_ofs), .strobe_out());
+   
+   add2_and_clip_reg #(.WIDTH(24)) add_dco_q
+     (.clk(clk), .rst(rst), .in1(q_dco), .in2(q_bal), .strobe_in(1'b1), .sum(q_ofs), .strobe_out());
+
+   // Rounding
+   round_sd #(.WIDTH_IN(24),.WIDTH_OUT(WIDTH_OUT)) round_i
+     (.clk(clk), .reset(rst), .in(i_ofs),.strobe_in(1'b1), .out(i_final), .strobe_out());
+
+   round_sd #(.WIDTH_IN(24),.WIDTH_OUT(WIDTH_OUT)) round_q
+     (.clk(clk), .reset(rst), .in(q_ofs),.strobe_in(1'b1), .out(q_final), .strobe_out());
+
+   // Mux
+   always @(posedge clk)
+     case(mux_ctrl[3:0])
+       0 : dac_a <= i_final;
+       1 : dac_a <= q_final;
+       default : dac_a <= 0;
+     endcase // case (mux_ctrl[3:0])
+      
+   always @(posedge clk)
+     case(mux_ctrl[7:4])
+       0 : dac_b <= i_final;
+       1 : dac_b <= q_final;
+       default : dac_b <= 0;
+     endcase // case (mux_ctrl[7:4])
+      
+endmodule // tx_frontend