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81 lines
2.6 KiB
Verilog
81 lines
2.6 KiB
Verilog
//-----------------------------------------------------------------------------
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// Copyright (C) Proxmark3 contributors. See AUTHORS.md for details.
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// See LICENSE.txt for the text of the license.
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//-----------------------------------------------------------------------------
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//
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// track min and max peak values (envelope follower)
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//
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// NB: the min value (resp. max value) is updated only when the next high peak
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// (resp. low peak) is reached/detected, since you can't know it isn't a
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// local minima (resp. maxima) until then.
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// This also means the peaks are detected with an unpredictable delay.
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// This algorithm therefore can't be used directly for realtime peak detections,
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// but it can be used as a simple envelope follower.
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module min_max_tracker(
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input clk,
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input [7:0] adc_d,
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input [7:0] threshold,
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output [7:0] min,
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output [7:0] max
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);
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reg [7:0] min_val = 255;
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reg [7:0] max_val = 0;
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reg [7:0] cur_min_val = 255;
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reg [7:0] cur_max_val = 0;
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reg [1:0] state = 0;
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always @(posedge clk)
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begin
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case (state)
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0: // initialize
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begin
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if (cur_max_val >= ({1'b0, adc_d} + threshold))
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state <= 2;
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else if (adc_d >= ({1'b0, cur_min_val} + threshold))
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state <= 1;
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if (cur_max_val <= adc_d)
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cur_max_val <= adc_d;
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else if (adc_d <= cur_min_val)
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cur_min_val <= adc_d;
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end
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1: // high phase
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begin
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if (cur_max_val <= adc_d)
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cur_max_val <= adc_d;
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else if (({1'b0, adc_d} + threshold) <= cur_max_val) begin
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state <= 2;
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cur_min_val <= adc_d;
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max_val <= cur_max_val;
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end
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end
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2: // low phase
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begin
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if (adc_d <= cur_min_val)
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cur_min_val <= adc_d;
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else if (adc_d >= ({1'b0, cur_min_val} + threshold)) begin
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state <= 1;
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cur_max_val <= adc_d;
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min_val <= cur_min_val;
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end
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end
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endcase
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end
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assign min = min_val;
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assign max = max_val;
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endmodule
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