+++ /dev/null
-//-----------------------------------------------------------------------------
-//
-// Jonathan Westhues, April 2006
-//-----------------------------------------------------------------------------
-
-module hi_read_rx_xcorr(
- pck0, ck_1356meg, ck_1356megb,
- pwr_lo, pwr_hi, pwr_oe1, pwr_oe2, pwr_oe3, pwr_oe4,
- adc_d, adc_clk,
- ssp_frame, ssp_din, ssp_dout, ssp_clk,
- cross_hi, cross_lo,
- dbg,
- xcorr_is_848, snoop, xcorr_quarter_freq
-);
- input pck0, ck_1356meg, ck_1356megb;
- output pwr_lo, pwr_hi, pwr_oe1, pwr_oe2, pwr_oe3, pwr_oe4;
- input [7:0] adc_d;
- output adc_clk;
- input ssp_dout;
- output ssp_frame, ssp_din, ssp_clk;
- input cross_hi, cross_lo;
- output dbg;
- input xcorr_is_848, snoop, xcorr_quarter_freq;
-
-// Carrier is steady on through this, unless we're snooping.
-assign pwr_hi = ck_1356megb & (~snoop);
-assign pwr_oe1 = 1'b0;
-assign pwr_oe2 = 1'b0;
-assign pwr_oe3 = 1'b0;
-assign pwr_oe4 = 1'b0;
-
-reg ssp_clk;
-reg ssp_frame;
-
-reg fc_div_2;
-always @(posedge ck_1356meg)
- fc_div_2 = ~fc_div_2;
-
-reg fc_div_4;
-always @(posedge fc_div_2)
- fc_div_4 = ~fc_div_4;
-
-reg fc_div_8;
-always @(posedge fc_div_4)
- fc_div_8 = ~fc_div_8;
-
-reg adc_clk;
-
-always @(xcorr_is_848 or xcorr_quarter_freq or ck_1356meg)
- if(~xcorr_quarter_freq)
- begin
- if(xcorr_is_848)
- // The subcarrier frequency is fc/16; we will sample at fc, so that
- // means the subcarrier is 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 ...
- adc_clk <= ck_1356meg;
- else
- // The subcarrier frequency is fc/32; we will sample at fc/2, and
- // the subcarrier will look identical.
- adc_clk <= fc_div_2;
- end
- else
- begin
- if(xcorr_is_848)
- // The subcarrier frequency is fc/64
- adc_clk <= fc_div_4;
- else
- // The subcarrier frequency is fc/128
- adc_clk <= fc_div_8;
- end
-
-// When we're a reader, we just need to do the BPSK demod; but when we're an
-// eavesdropper, we also need to pick out the commands sent by the reader,
-// using AM. Do this the same way that we do it for the simulated tag.
-reg after_hysteresis, after_hysteresis_prev;
-reg [11:0] has_been_low_for;
-always @(negedge adc_clk)
-begin
- if(& adc_d[7:0]) after_hysteresis <= 1'b1;
- else if(~(| adc_d[7:0])) after_hysteresis <= 1'b0;
-
- if(after_hysteresis)
- begin
- has_been_low_for <= 7'b0;
- end
- else
- begin
- if(has_been_low_for == 12'd4095)
- begin
- has_been_low_for <= 12'd0;
- after_hysteresis <= 1'b1;
- end
- else
- has_been_low_for <= has_been_low_for + 1;
- end
-end
-
-// Let us report a correlation every 4 subcarrier cycles, or 4*16 samples,
-// so we need a 6-bit counter.
-reg [5:0] corr_i_cnt;
-reg [5:0] corr_q_cnt;
-// And a couple of registers in which to accumulate the correlations.
-reg signed [15:0] corr_i_accum;
-reg signed [15:0] corr_q_accum;
-reg signed [7:0] corr_i_out;
-reg signed [7:0] corr_q_out;
-
-// ADC data appears on the rising edge, so sample it on the falling edge
-always @(negedge adc_clk)
-begin
- // These are the correlators: we correlate against in-phase and quadrature
- // versions of our reference signal, and keep the (signed) result to
- // send out later over the SSP.
- if(corr_i_cnt == 7'd63)
- begin
- if(snoop)
- begin
- corr_i_out <= {corr_i_accum[12:6], after_hysteresis_prev};
- corr_q_out <= {corr_q_accum[12:6], after_hysteresis};
- end
- else
- begin
- // Only correlations need to be delivered.
- corr_i_out <= corr_i_accum[13:6];
- corr_q_out <= corr_q_accum[13:6];
- end
-
- corr_i_accum <= adc_d;
- corr_q_accum <= adc_d;
- corr_q_cnt <= 4;
- corr_i_cnt <= 0;
- end
- else
- begin
- if(corr_i_cnt[3])
- corr_i_accum <= corr_i_accum - adc_d;
- else
- corr_i_accum <= corr_i_accum + adc_d;
-
- if(corr_q_cnt[3])
- corr_q_accum <= corr_q_accum - adc_d;
- else
- corr_q_accum <= corr_q_accum + adc_d;
-
- corr_i_cnt <= corr_i_cnt + 1;
- corr_q_cnt <= corr_q_cnt + 1;
- end
-
- // The logic in hi_simulate.v reports 4 samples per bit. We report two
- // (I, Q) pairs per bit, so we should do 2 samples per pair.
- if(corr_i_cnt == 6'd31)
- after_hysteresis_prev <= after_hysteresis;
-
- // Then the result from last time is serialized and send out to the ARM.
- // We get one report each cycle, and each report is 16 bits, so the
- // ssp_clk should be the adc_clk divided by 64/16 = 4.
-
- if(corr_i_cnt[1:0] == 2'b10)
- ssp_clk <= 1'b0;
-
- if(corr_i_cnt[1:0] == 2'b00)
- begin
- ssp_clk <= 1'b1;
- // Don't shift if we just loaded new data, obviously.
- if(corr_i_cnt != 7'd0)
- begin
- corr_i_out[7:0] <= {corr_i_out[6:0], corr_q_out[7]};
- corr_q_out[7:1] <= corr_q_out[6:0];
- end
- end
-
- if(corr_i_cnt[5:2] == 4'b000 || corr_i_cnt[5:2] == 4'b1000)
- ssp_frame = 1'b1;
- else
- ssp_frame = 1'b0;
-
-end
-
-assign ssp_din = corr_i_out[7];
-
-assign dbg = corr_i_cnt[3];
-
-// Unused.
-assign pwr_lo = 1'b0;
-
-endmodule
projects / proxmark3-svn / blobdiff