Unified fpga folders

fpga/min_max_tracker.v

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+//-----------------------------------------------------------------------------
+// Copyright (C) Proxmark3 contributors. See AUTHORS.md for details.
+//
+// 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.
+//
+// See LICENSE.txt for the text of the license.
+//-----------------------------------------------------------------------------
+//
+// track min and max peak values (envelope follower)
+//
+// NB: the min value (resp. max value) is updated only when the next high peak
+// (resp. low peak) is reached/detected, since you can't know it isn't a
+// local minima (resp. maxima) until then.
+// This also means the peaks are detected with an unpredictable delay.
+// This algorithm therefore can't be used directly for realtime peak detections,
+// but it can be used as a simple envelope follower.
+
+module min_max_tracker(
+    input clk,
+    input [7:0] adc_d,
+    input [7:0] threshold,
+    output [7:0] min,
+    output [7:0] max
+);
+
+    reg [7:0] min_val = 255;
+    reg [7:0] max_val = 0;
+    reg [7:0] cur_min_val = 255;
+    reg [7:0] cur_max_val = 0;
+    reg [1:0] state = 0;
+
+    always @(posedge clk)
+    begin
+        case (state)
+        0: // initialize
+            begin
+                if (cur_max_val >= ({1'b0, adc_d} + threshold))
+                    state <= 2;
+                else if (adc_d >= ({1'b0, cur_min_val} + threshold))
+                    state <= 1;
+                if (cur_max_val <= adc_d)
+                    cur_max_val <= adc_d;
+                else if (adc_d <= cur_min_val)
+                    cur_min_val <= adc_d;
+            end
+        1: // high phase
+            begin
+                if (cur_max_val <= adc_d)
+                    cur_max_val <= adc_d;
+                else if (({1'b0, adc_d} + threshold) <= cur_max_val) begin
+                    state <= 2;
+                    cur_min_val <= adc_d;
+                    max_val <= cur_max_val;
+                end
+            end
+        2: // low phase
+            begin
+                if (adc_d <= cur_min_val)
+                    cur_min_val <= adc_d;
+                else if (adc_d >= ({1'b0, cur_min_val} + threshold)) begin
+                    state <= 1;
+                    cur_max_val <= adc_d;
+                    min_val <= cur_min_val;
+                end
+            end
+        endcase
+    end
+
+    assign min = min_val;
+    assign max = max_val;
+
+endmodule