//----------------------------------------------------------------------------- // Copyright (C) 2014 iZsh // // 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 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: 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