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[proxmark3-svn] / fpga / hi_read_rx_xcorr.v
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ba06a4b6 1//-----------------------------------------------------------------------------
2//
3// Jonathan Westhues, April 2006
4//-----------------------------------------------------------------------------
5
6module hi_read_rx_xcorr(
7 pck0, ck_1356meg, ck_1356megb,
8 pwr_lo, pwr_hi, pwr_oe1, pwr_oe2, pwr_oe3, pwr_oe4,
9 adc_d, adc_clk,
10 ssp_frame, ssp_din, ssp_dout, ssp_clk,
11 cross_hi, cross_lo,
12 dbg,
da586b17 13 xcorr_is_848, snoop
ba06a4b6 14);
15 input pck0, ck_1356meg, ck_1356megb;
16 output pwr_lo, pwr_hi, pwr_oe1, pwr_oe2, pwr_oe3, pwr_oe4;
17 input [7:0] adc_d;
18 output adc_clk;
19 input ssp_dout;
20 output ssp_frame, ssp_din, ssp_clk;
21 input cross_hi, cross_lo;
22 output dbg;
da586b17 23 input xcorr_is_848, snoop;
ba06a4b6 24
25// Carrier is steady on through this, unless we're snooping.
26assign pwr_hi = ck_1356megb & (~snoop);
27assign pwr_oe1 = 1'b0;
ba06a4b6 28assign pwr_oe3 = 1'b0;
29assign pwr_oe4 = 1'b0;
30
b535053a 31// Clock divider
32reg [0:0] fc_divider;
da586b17 33always @(negedge ck_1356megb)
b535053a 34 fc_divider <= fc_divider + 1;
35wire fc_div2 = fc_divider[0];
36
37reg adc_clk;
38always @(ck_1356megb)
39 if (xcorr_is_848)
40 adc_clk <= ck_1356megb;
41 else
42 adc_clk <= fc_div2;
ba06a4b6 43
44// When we're a reader, we just need to do the BPSK demod; but when we're an
45// eavesdropper, we also need to pick out the commands sent by the reader,
46// using AM. Do this the same way that we do it for the simulated tag.
51d4f6f1 47reg after_hysteresis, after_hysteresis_prev, after_hysteresis_prev_prev;
ba06a4b6 48reg [11:0] has_been_low_for;
49always @(negedge adc_clk)
50begin
51 if(& adc_d[7:0]) after_hysteresis <= 1'b1;
52 else if(~(| adc_d[7:0])) after_hysteresis <= 1'b0;
53
54 if(after_hysteresis)
55 begin
56 has_been_low_for <= 7'b0;
57 end
58 else
59 begin
60 if(has_been_low_for == 12'd4095)
61 begin
62 has_been_low_for <= 12'd0;
63 after_hysteresis <= 1'b1;
64 end
65 else
66 has_been_low_for <= has_been_low_for + 1;
67 end
68end
69
70// Let us report a correlation every 4 subcarrier cycles, or 4*16 samples,
71// so we need a 6-bit counter.
72reg [5:0] corr_i_cnt;
ba06a4b6 73// And a couple of registers in which to accumulate the correlations.
5b95953d 74// we would add at most 32 times adc_d, the result can be held in 13 bits.
75// Need one additional bit because it can be negative as well
76reg signed [13:0] corr_i_accum;
77reg signed [13:0] corr_q_accum;
ba06a4b6 78reg signed [7:0] corr_i_out;
79reg signed [7:0] corr_q_out;
51d4f6f1 80// clock and frame signal for communication to ARM
81reg ssp_clk;
82reg ssp_frame;
83
84
46734099 85always @(negedge adc_clk)
86begin
46734099 87 corr_i_cnt <= corr_i_cnt + 1;
88end
89
ba06a4b6 90
91// ADC data appears on the rising edge, so sample it on the falling edge
92always @(negedge adc_clk)
93begin
94 // These are the correlators: we correlate against in-phase and quadrature
95 // versions of our reference signal, and keep the (signed) result to
96 // send out later over the SSP.
705bfa10 97 if(corr_i_cnt == 6'd0)
ba06a4b6 98 begin
99 if(snoop)
100 begin
46734099 101 // Send only 7 most significant bits of tag signal (signed), LSB is reader signal:
51d4f6f1 102 corr_i_out <= {corr_i_accum[13:7], after_hysteresis_prev_prev};
103 corr_q_out <= {corr_q_accum[13:7], after_hysteresis_prev};
104 after_hysteresis_prev_prev <= after_hysteresis;
ba06a4b6 105 end
106 else
107 begin
51d4f6f1 108 // 8 most significant bits of tag signal
ba06a4b6 109 corr_i_out <= corr_i_accum[13:6];
110 corr_q_out <= corr_q_accum[13:6];
111 end
112
113 corr_i_accum <= adc_d;
114 corr_q_accum <= adc_d;
ba06a4b6 115 end
116 else
117 begin
118 if(corr_i_cnt[3])
119 corr_i_accum <= corr_i_accum - adc_d;
120 else
121 corr_i_accum <= corr_i_accum + adc_d;
122
51d4f6f1 123 if(corr_i_cnt[3] == corr_i_cnt[2]) // phase shifted by pi/2
ba06a4b6 124 corr_q_accum <= corr_q_accum + adc_d;
51d4f6f1 125 else
126 corr_q_accum <= corr_q_accum - adc_d;
ba06a4b6 127
ba06a4b6 128 end
129
130 // The logic in hi_simulate.v reports 4 samples per bit. We report two
131 // (I, Q) pairs per bit, so we should do 2 samples per pair.
705bfa10 132 if(corr_i_cnt == 6'd32)
ba06a4b6 133 after_hysteresis_prev <= after_hysteresis;
134
135 // Then the result from last time is serialized and send out to the ARM.
136 // We get one report each cycle, and each report is 16 bits, so the
137 // ssp_clk should be the adc_clk divided by 64/16 = 4.
138
139 if(corr_i_cnt[1:0] == 2'b10)
140 ssp_clk <= 1'b0;
141
142 if(corr_i_cnt[1:0] == 2'b00)
143 begin
144 ssp_clk <= 1'b1;
145 // Don't shift if we just loaded new data, obviously.
b535053a 146 if(corr_i_cnt != 6'd0)
ba06a4b6 147 begin
148 corr_i_out[7:0] <= {corr_i_out[6:0], corr_q_out[7]};
149 corr_q_out[7:1] <= corr_q_out[6:0];
150 end
151 end
152
09c66f1f 153 // set ssp_frame signal for corr_i_cnt = 0..3 and corr_i_cnt = 32..35
51d4f6f1 154 // (send two frames with 8 Bits each)
09c66f1f 155 if(corr_i_cnt[5:2] == 4'b0000 || corr_i_cnt[5:2] == 4'b1000)
ba06a4b6 156 ssp_frame = 1'b1;
157 else
158 ssp_frame = 1'b0;
159
160end
161
162assign ssp_din = corr_i_out[7];
163
164assign dbg = corr_i_cnt[3];
165
166// Unused.
167assign pwr_lo = 1'b0;
51d4f6f1 168assign pwr_oe2 = 1'b0;
ba06a4b6 169
170endmodule
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