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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 //
9 // There are two modes:
10 // - lf_ed_toggle_mode == 0: the output is set low (resp. high) when a low
11 // (resp. high) edge/peak is detected, with hysteresis
12 // - lf_ed_toggle_mode == 1: the output is toggling whenever an edge/peak
13 // is detected.
14 // That way you can detect two consecutive edges/peaks at the same level (L/H)
15 //
16 // Output:
17 // - ssp_frame (wired to TIOA1 on the arm) for the edge detection/state
18 // - ssp_clk: cross_lo
19 `include "lp20khz_1MSa_iir_filter.v"
20 `include "lf_edge_detect.v"
21
22 module lo_edge_detect(
23 input pck0, input pck_divclk,
24 output pwr_lo, output pwr_hi,
25 output pwr_oe1, output pwr_oe2, output pwr_oe3, output pwr_oe4,
26 input [7:0] adc_d, output adc_clk,
27 output ssp_frame, input ssp_dout, output ssp_clk,
28 input cross_lo,
29 output dbg,
30 input lf_field,
31 input lf_ed_toggle_mode, input [7:0] lf_ed_threshold
32 );
33
34 wire tag_modulation = ssp_dout & !lf_field;
35 wire reader_modulation = !ssp_dout & lf_field & pck_divclk;
36
37 // No logic, straight through.
38 assign pwr_oe1 = 1'b0; // not used in LF mode
39 assign pwr_oe2 = tag_modulation;
40 assign pwr_oe3 = tag_modulation;
41 assign pwr_oe4 = tag_modulation;
42 assign ssp_clk = cross_lo;
43 assign pwr_lo = reader_modulation;
44 assign pwr_hi = 1'b0;
45
46 // filter the ADC values
47 wire data_rdy;
48 wire [7:0] adc_filtered;
49 assign adc_clk = pck0;
50 lp20khz_1MSa_iir_filter adc_filter(pck0, adc_d, data_rdy, adc_filtered);
51
52 // detect edges
53 wire [7:0] high_threshold, highz_threshold, lowz_threshold, low_threshold;
54 wire [7:0] max, min;
55 wire edge_state, edge_toggle;
56 lf_edge_detect lf_ed(pck0, adc_filtered, lf_ed_threshold,
57 max, min,
58 high_threshold, highz_threshold, lowz_threshold, low_threshold,
59 edge_state, edge_toggle);
60
61 assign dbg = lf_ed_toggle_mode ? edge_toggle : edge_state;
62
63 assign ssp_frame = lf_ed_toggle_mode ? edge_toggle : edge_state;
64
65 endmodule
66
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