| 1 | //----------------------------------------------------------------------------- |
| 2 | // Copyright (C) 2014 iZsh <izsh at fail0verflow.com> |
| 3 | // |
| 4 | // This code is licensed to you under the terms of the GNU GPL, version 2 or, |
| 5 | // at your option, any later version. See the LICENSE.txt file for the text of |
| 6 | // the license. |
| 7 | //----------------------------------------------------------------------------- |
| 8 | // track min and max peak values (envelope follower) |
| 9 | // |
| 10 | // NB: the min value (resp. max value) is updated only when the next high peak |
| 11 | // (resp. low peak) is reached/detected, since you can't know it isn't a |
| 12 | // local minima (resp. maxima) until then. |
| 13 | // This also means the peaks are detected with an unpredictable delay. |
| 14 | // This algorithm therefore can't be used directly for realtime peak detections, |
| 15 | // but it can be used as a simple envelope follower. |
| 16 | module min_max_tracker(input clk, input [7:0] adc_d, input [7:0] threshold, |
| 17 | output [7:0] min, output [7:0] max); |
| 18 | |
| 19 | reg [7:0] min_val = 255; |
| 20 | reg [7:0] max_val = 0; |
| 21 | reg [7:0] cur_min_val = 255; |
| 22 | reg [7:0] cur_max_val = 0; |
| 23 | reg [1:0] state = 0; |
| 24 | |
| 25 | always @(posedge clk) |
| 26 | begin |
| 27 | case (state) |
| 28 | 0: |
| 29 | begin |
| 30 | if (cur_max_val >= ({1'b0, adc_d} + threshold)) |
| 31 | state <= 2; |
| 32 | else if (adc_d >= ({1'b0, cur_min_val} + threshold)) |
| 33 | state <= 1; |
| 34 | if (cur_max_val <= adc_d) |
| 35 | cur_max_val <= adc_d; |
| 36 | else if (adc_d <= cur_min_val) |
| 37 | cur_min_val <= adc_d; |
| 38 | end |
| 39 | 1: |
| 40 | begin |
| 41 | if (cur_max_val <= adc_d) |
| 42 | cur_max_val <= adc_d; |
| 43 | else if (({1'b0, adc_d} + threshold) <= cur_max_val) begin |
| 44 | state <= 2; |
| 45 | cur_min_val <= adc_d; |
| 46 | max_val <= cur_max_val; |
| 47 | end |
| 48 | end |
| 49 | 2: |
| 50 | begin |
| 51 | if (adc_d <= cur_min_val) |
| 52 | cur_min_val <= adc_d; |
| 53 | else if (adc_d >= ({1'b0, cur_min_val} + threshold)) begin |
| 54 | state <= 1; |
| 55 | cur_max_val <= adc_d; |
| 56 | min_val <= cur_min_val; |
| 57 | end |
| 58 | end |
| 59 | endcase |
| 60 | end |
| 61 | |
| 62 | assign min = min_val; |
| 63 | assign max = max_val; |
| 64 | |
| 65 | endmodule |