From ef5a7328480827084d6c86e71f54c66bb42a2645 Mon Sep 17 00:00:00 2001
From: Matt Ettus <matt@ettus.com>
Date: Thu, 24 Sep 2009 12:33:22 -0700
Subject: [PATCH] Synchronize the internal phase of the halfband filters to the
 start of the "run" signal.  This is important for MIMO.  Bug reported by
 Christoph Hein and Hanwen .

---
 usrp2/fpga/sdr_lib/dsp_core_rx.v  |  8 ++++----
 usrp2/fpga/sdr_lib/hb_dec.v       |  5 +++--
 usrp2/fpga/sdr_lib/small_hb_dec.v | 22 +++++++++++++++++-----
 3 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/usrp2/fpga/sdr_lib/dsp_core_rx.v b/usrp2/fpga/sdr_lib/dsp_core_rx.v
index ee713e4a..af4f0b9f 100644
--- a/usrp2/fpga/sdr_lib/dsp_core_rx.v
+++ b/usrp2/fpga/sdr_lib/dsp_core_rx.v
@@ -139,20 +139,20 @@ module dsp_core_rx
    always @(posedge clk) strobe_cic_d1 <= strobe_cic;
    
    small_hb_dec #(.WIDTH(18)) small_hb_i
-     (.clk(clk),.rst(rst),.bypass(~enable_hb1),
+     (.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));
    
    small_hb_dec #(.WIDTH(18)) small_hb_q
-     (.clk(clk),.rst(rst),.bypass(~enable_hb1),
+     (.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));
 
    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
-     (.clk(clk),.rst(rst),.bypass(~enable_hb2),.cpi(cpi_hb),
+     (.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
-     (.clk(clk),.rst(rst),.bypass(~enable_hb2),.cpi(cpi_hb),
+     (.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));
diff --git a/usrp2/fpga/sdr_lib/hb_dec.v b/usrp2/fpga/sdr_lib/hb_dec.v
index b256eb57..8fb5ba22 100644
--- a/usrp2/fpga/sdr_lib/hb_dec.v
+++ b/usrp2/fpga/sdr_lib/hb_dec.v
@@ -9,6 +9,7 @@ module hb_dec
     (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,
@@ -25,7 +26,7 @@ module hb_dec
    assign 		do_mult = 1;
    
    always @(posedge clk)
-     if(rst)
+     if(rst | ~run)
        odd <= 0;
      else if(stb_in)
        odd <= ~odd;
@@ -34,7 +35,7 @@ module hb_dec
    assign 		write_even = stb_in & ~odd;
 
    always @(posedge clk)
-     if(rst)
+     if(rst | ~run)
        phase <= 0;
      else if(stb_in & odd)
        phase <= 1;
diff --git a/usrp2/fpga/sdr_lib/small_hb_dec.v b/usrp2/fpga/sdr_lib/small_hb_dec.v
index 9957de15..8519b628 100644
--- a/usrp2/fpga/sdr_lib/small_hb_dec.v
+++ b/usrp2/fpga/sdr_lib/small_hb_dec.v
@@ -8,6 +8,7 @@ module small_hb_dec
     (input clk,
      input rst,
      input bypass,
+     input run,
      input stb_in,
      input [WIDTH-1:0] data_in,
      output reg stb_out,
@@ -21,15 +22,26 @@ module small_hb_dec
    wire 		go;
    reg 			phase, go_d1, go_d2, go_d3, go_d4;
    always @(posedge clk)
-     if(rst)
+     if(rst | ~run)
        phase <= 0;
      else if(stb_in_d1)
        phase <= ~phase;
    assign 		go = stb_in_d1 & phase;
-   always @(posedge clk) go_d1 <= go;
-   always @(posedge clk) go_d2 <= go_d1;
-   always @(posedge clk) go_d3 <= go_d2;
-   always @(posedge clk) go_d4 <= go_d3;
+   always @(posedge clk) 
+     if(rst | ~run)
+       begin
+	  go_d1 <= 0;
+	  go_d2 <= 0;
+	  go_d3 <= 0;
+	  go_d4 <= 0;
+       end
+     else
+       begin
+	  go_d1 <= go;
+	  go_d2 <= go_d1;
+	  go_d3 <= go_d2;
+	  go_d4 <= go_d3;
+       end
 
    wire [17:0] 		coeff_a = -10690;
    wire [17:0] 		coeff_b = 75809;
-- 
2.39.5