X-Git-Url: https://git.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/e17437f985b1c955b3a2e3cab4f9146db54631a1..3b2fee43ea7d9e08b7729d662d8d010ee0e2a2e3:/fpga/min_max_tracker.v

diff --git a/fpga/min_max_tracker.v b/fpga/min_max_tracker.v
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+//-----------------------------------------------------------------------------
+// Copyright (C) 2014 iZsh <izsh at fail0verflow.com>
+//
+// This code is licensed to you under the terms of the GNU GPL, version 2 or,
+// at your option, any later version. See the LICENSE.txt file 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 can't therefore 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:
+			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:
+			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:
+			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