m2k:axi_ad9963, axi_dac_interpolate fixes

This commit fixes the last sample hold and spike before buffers
at low samplerates by compensating for the interpolation filter delays.

Signed-off-by: AndreiGrozav <andrei.grozav@analog.com>

Author: AndreiGrozav

library/axi_ad9963/axi_ad9963_tx_channel.v

@@ -1,6 +1,6 @@
 // ***************************************************************************
 // ***************************************************************************
-// Copyright (C) 2017-2023 Analog Devices, Inc. All rights reserved.
+// Copyright (C) 2017-2024 Analog Devices, Inc. All rights reserved.
 //
 // In this HDL repository, there are many different and unique modules, consisting
 // of various HDL (Verilog or VHDL) components. The individual modules are
@@ -88,7 +88,6 @@ module axi_ad9963_tx_channel #(
   // internal registers
 
   reg             dac_valid_sel = 'd0;
-  reg             data_source_valid = 'd0;
   reg     [23:0]  dac_test_data = 'd0;
   reg     [15:0]  dac_test_counter = 'd0;
   reg     [15:0]  dac_pat_data = 'd0;
@@ -111,27 +110,29 @@ module axi_ad9963_tx_channel #(
   wire            dac_iqcor_enb_s;
   wire    [15:0]  dac_iqcor_coeff_1_s;
   wire    [15:0]  dac_iqcor_coeff_2_s;
+  wire            data_source_valid_s;
 
   // dac iq correction
 
   always @(posedge dac_clk) begin
-    data_source_valid <= dac_data_sel_s == 4'h2 ? dma_valid_m : dac_valid;
     dac_enable <= (dac_data_sel_s == 4'h2) ? 1'b1 : 1'b0;
     if (dac_iqcor_valid_s == 1'b1) begin
       dac_data <= dac_iqcor_data_s[15:4];
     end
   end
 
+  assign data_source_valid_s = dac_data_sel_s == 4'h2 ? dma_valid_m : dac_valid;
+
   generate
   if (DATAPATH_DISABLE == 1) begin
-  assign dac_iqcor_valid_s = data_source_valid;
+  assign dac_iqcor_valid_s = data_source_valid_s;
   assign dac_iqcor_data_s = {dac_data_out, 4'd0};
   end else begin
   ad_iqcor #(
     .Q_OR_I_N (Q_OR_I_N)
   ) i_ad_iqcor (
     .clk (dac_clk),
-    .valid (data_source_valid),
+    .valid (data_source_valid_s),
     .data_in ({dac_data_out, 4'd0}),
     .data_iq ({dac_data_in, 4'd0}),
     .valid_out (dac_iqcor_valid_s),

library/axi_dac_interpolate/axi_dac_interpolate_filter.v

@@ -88,15 +88,17 @@ module axi_dac_interpolate_filter #(
   reg               cic_change_rate;
   reg     [31:0]    interpolation_counter;
 
-  reg               filter_enable = 1'b0;
   reg     [15:0]    dma_valid_m = 16'd0;
+  reg     [15:0]    reset_filt_m = 16'd0;
   reg               stop_transfer = 1'd0;
   reg               clear_stop_flag = 1'd0;
 
   reg               transfer = 1'd0;
   reg     [ 1:0]    transfer_sm = 2'd0;
   reg     [ 1:0]    transfer_sm_next = 2'd0;
   reg               raw_dma_n = 1'd0;
+  reg               last_m = 1'd0;
+  reg               dac_int_ready_residual;
 
   // internal signals
 
@@ -128,8 +130,6 @@ module axi_dac_interpolate_filter #(
     raw_dma_n <= raw_transfer_en | flush_dma ? 1'b1 : raw_dma_n & !dma_valid;
   end
 
-  assign reset_filt = !raw_dma_n & dma_transfer_suspend;
-
   assign iqcor_data_in  = raw_dma_n ? dac_raw_ch_data : dac_data;
   assign iqcor_valid_in = raw_dma_n ? 1'b1 : dac_valid;
 
@@ -175,10 +175,6 @@ module axi_dac_interpolate_filter #(
     end
   end
 
-  // - for start synchronized, wait until the DMA has valid data on both channels
-  // - for non synchronized channels the start of transmission gets the 2 data
-  // paths randomly ready, only when using data buffers
-
   always @(posedge dac_clk) begin
     if (dac_filt_int_valid & transfer_ready) begin
       if (interpolation_counter == interpolation_ratio) begin
@@ -194,13 +190,22 @@ module axi_dac_interpolate_filter #(
     end
   end
 
+  always @(posedge dac_clk) begin
+    last_m <= last;
+  end
+
+  // - for start synchronized, wait until the DMA has valid data on both channels
+  // - for non synchronized channels the start of transmission gets the 2 data
+  // paths randomly ready, only when using data buffers
+
   assign transfer_ready =  start_sync_channels ?
                              dma_valid & dma_valid_adjacent :
                              dma_valid;
   assign transfer_start = !(en_start_trigger ^ trigger) &
                           transfer_ready & !dma_transfer_suspend;
 
-  assign rearm_channel = last & rearm_on_last;
+  assign rearm_channel = ~last_m & last & rearm_on_last; // re-arm on last rise
+
   always @(posedge dac_clk) begin
     stop_transfer <= transfer_sm == IDLE ? 1'b0 :
                      (stop_transfer & !clear_stop_flag) |
@@ -258,29 +263,38 @@ module axi_dac_interpolate_filter #(
 
   always @(posedge dac_clk) begin
     if (dac_rst == 1'b1) begin
-      dma_valid_m <= 'd0;
+      dma_valid_m <= 16'h0;
     end else begin
-      dma_valid_m <= {dma_valid_m[14:0], dma_valid_ch};
+      if (dac_filt_int_valid == 1'b1) begin
+        dma_valid_m <= {dma_valid_m[14:0], dma_valid_ch};
+      end
     end
   end
 
-  assign dac_valid_out = dma_valid_m[2];
-
   always @(posedge dac_clk) begin
-    case (filter_mask)
-      3'b000: filter_enable <= 1'b0;
-      default: filter_enable <= 1'b1;
-    endcase
+    if (dac_rst == 1'b1) begin
+      reset_filt_m <= 16'hffff;
+    end else begin
+      if (dac_filt_int_valid == 1'b1) begin
+        reset_filt_m <= {reset_filt_m[14:0], dma_transfer_suspend};
+      end else if (dma_transfer_suspend == 1'b0) begin
+        reset_filt_m <= 16'h0;
+      end
+    end
   end
 
+  // compensate fir cic filter
+  assign dac_valid_out = |filter_mask ? dma_valid_m[13] : dma_valid_m[2];
+  assign reset_filt = !raw_dma_n & reset_filt_m[13];
+
   always @(*) begin
-    case (filter_enable)
-      1'b0: dac_int_data = dac_data_corrected;
+    case (filter_mask)
+      3'b000: dac_int_data = dac_data_corrected;
       default: dac_int_data = dac_cic_data[31:16];
     endcase
 
     case (filter_mask)
-      1'b0: dac_filt_int_valid = dac_valid_corrected & !dma_transfer_suspend;
+      1'b0: dac_filt_int_valid = dac_valid_corrected;
       default: dac_filt_int_valid = dac_fir_valid;
     endcase