+++ /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, hi_read_rx_xcorr_amplitude
-);
- 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, hi_read_rx_xcorr_amplitude;
-
-// Carrier is steady on through this, unless we're snooping.
-assign pwr_hi = ck_1356megb & (~snoop);
-assign pwr_oe1 = 1'b0;
-assign pwr_oe3 = 1'b0;
-assign pwr_oe4 = 1'b0;
-// Unused.
-assign pwr_lo = 1'b0;
-assign pwr_oe2 = 1'b0;
-
-assign adc_clk = ck_1356megb; // sample frequency is 13,56 MHz
-
-// 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, after_hysteresis_prev_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 64 samples. I.e.
-// one Q/I pair after 4 subcarrier cycles for the 848kHz subcarrier,
-// one Q/I pair after 2 subcarrier cycles for the 424kHz subcarriers,
-// one Q/I pair for each subcarrier cyle for the 212kHz subcarrier.
-// We need a 6-bit counter for the timing.
-reg [5:0] corr_i_cnt;
-always @(negedge adc_clk)
-begin
- corr_i_cnt <= corr_i_cnt + 1;
-end
-
-// And a couple of registers in which to accumulate the correlations. From the 64 samples
-// we would add at most 32 times the difference between unmodulated and modulated signal. It should
-// be safe to assume that a tag will not be able to modulate the carrier signal by more than 25%.
-// 32 * 255 * 0,25 = 2040, which can be held in 11 bits. Add 1 bit for sign.
-// Temporary we might need more bits. For the 212kHz subcarrier we could possible add 32 times the
-// maximum signal value before a first subtraction would occur. 32 * 255 = 8160 can be held in 13 bits.
-// Add one bit for sign -> need 14 bit registers but final result will fit into 12 bits.
-reg signed [13:0] corr_i_accum;
-reg signed [13:0] corr_q_accum;
-// we will report maximum 8 significant bits
-reg signed [7:0] corr_i_out;
-reg signed [7:0] corr_q_out;
-
-// clock and frame signal for communication to ARM
-reg ssp_clk;
-reg ssp_frame;
-
-
-
-// the amplitude of the subcarrier is sqrt(ci^2 + cq^2).
-// approximate by amplitude = max(|ci|,|cq|) + 1/2*min(|ci|,|cq|)
-reg [13:0] corr_amplitude, abs_ci, abs_cq, max_ci_cq, min_ci_cq;
-
-
-always @(corr_i_accum or corr_q_accum)
-begin
- if (corr_i_accum[13] == 1'b0)
- abs_ci <= corr_i_accum;
- else
- abs_ci <= -corr_i_accum;
-
- if (corr_q_accum[13] == 1'b0)
- abs_cq <= corr_q_accum;
- else
- abs_cq <= -corr_q_accum;
-
- if (abs_ci > abs_cq)
- begin
- max_ci_cq <= abs_ci;
- min_ci_cq <= abs_cq;
- end
- else
- begin
- max_ci_cq <= abs_cq;
- min_ci_cq <= abs_ci;
- end
-
- corr_amplitude <= max_ci_cq + min_ci_cq/2;
-
-end
-
-
-// The subcarrier reference signals
-reg subcarrier_I;
-reg subcarrier_Q;
-
-always @(corr_i_cnt or xcorr_is_848 or xcorr_quarter_freq)
-begin
- if (xcorr_is_848 & ~xcorr_quarter_freq) // 848 kHz
- begin
- subcarrier_I = ~corr_i_cnt[3];
- subcarrier_Q = ~(corr_i_cnt[3] ^ corr_i_cnt[2]);
- end
- else if (xcorr_is_848 & xcorr_quarter_freq) // 212 kHz
- begin
- subcarrier_I = ~corr_i_cnt[5];
- subcarrier_Q = ~(corr_i_cnt[5] ^ corr_i_cnt[4]);
- end
- else
- begin // 424 kHz
- subcarrier_I = ~corr_i_cnt[4];
- subcarrier_Q = ~(corr_i_cnt[4] ^ corr_i_cnt[3]);
- end
-end
-
-
-// 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) results or the
- // resulting amplitude to send out later over the SSP.
- if(corr_i_cnt == 6'd0)
- begin
- if(snoop)
- begin
- if (hi_read_rx_xcorr_amplitude)
- begin
- // send amplitude plus 2 bits reader signal
- corr_i_out <= corr_amplitude[13:6];
- corr_q_out <= {corr_amplitude[5:0], after_hysteresis_prev_prev, after_hysteresis_prev};
- end
- else
- begin
- // Send 7 most significant bits of in phase tag signal (signed), plus 1 bit reader signal
- if (corr_i_accum[13:11] == 3'b000 || corr_i_accum[13:11] == 3'b111)
- corr_i_out <= {corr_i_accum[11:5], after_hysteresis_prev_prev};
- else // truncate to maximum value
- if (corr_i_accum[13] == 1'b0)
- corr_i_out <= {7'b0111111, after_hysteresis_prev_prev};
- else
- corr_i_out <= {7'b1000000, after_hysteresis_prev_prev};
- // Send 7 most significant bits of quadrature phase tag signal (signed), plus 1 bit reader signal
- if (corr_q_accum[13:11] == 3'b000 || corr_q_accum[13:11] == 3'b111)
- corr_q_out <= {corr_q_accum[11:5], after_hysteresis_prev};
- else // truncate to maximum value
- if (corr_q_accum[13] == 1'b0)
- corr_q_out <= {7'b0111111, after_hysteresis_prev};
- else
- corr_q_out <= {7'b1000000, after_hysteresis_prev};
- end
- end
- else
- begin
- if (hi_read_rx_xcorr_amplitude)
- begin
- // send amplitude
- corr_i_out <= {2'b00, corr_amplitude[13:8]};
- corr_q_out <= corr_amplitude[7:0];
- end
- else
- begin
- // Send 8 bits of in phase tag signal
- if (corr_i_accum[13:11] == 3'b000 || corr_i_accum[13:11] == 3'b111)
- corr_i_out <= corr_i_accum[11:4];
- else // truncate to maximum value
- if (corr_i_accum[13] == 1'b0)
- corr_i_out <= 8'b01111111;
- else
- corr_i_out <= 8'b10000000;
- // Send 8 bits of quadrature phase tag signal
- if (corr_q_accum[13:11] == 3'b000 || corr_q_accum[13:11] == 3'b111)
- corr_q_out <= corr_q_accum[11:4];
- else // truncate to maximum value
- if (corr_q_accum[13] == 1'b0)
- corr_q_out <= 8'b01111111;
- else
- corr_q_out <= 8'b10000000;
- end
- end
-
- // for each Q/I pair report two reader signal samples when sniffing. Store the 1st.
- after_hysteresis_prev_prev <= after_hysteresis;
- // Initialize next correlation.
- // Both I and Q reference signals are high when corr_i_nct == 0. Therefore need to accumulate.
- corr_i_accum <= $signed({1'b0,adc_d});
- corr_q_accum <= $signed({1'b0,adc_d});
- end
- else
- begin
- if (subcarrier_I)
- corr_i_accum <= corr_i_accum + $signed({1'b0,adc_d});
- else
- corr_i_accum <= corr_i_accum - $signed({1'b0,adc_d});
-
- if (subcarrier_Q)
- corr_q_accum <= corr_q_accum + $signed({1'b0,adc_d});
- else
- corr_q_accum <= corr_q_accum - $signed({1'b0,adc_d});
- end
-
- // for each Q/I pair report two reader signal samples when sniffing. Store the 2nd.
- if(corr_i_cnt == 6'd32)
- 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.
- // ssp_clk frequency = 13,56MHz / 4 = 3.39MHz
-
- 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 != 6'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
-
- // set ssp_frame signal for corr_i_cnt = 0..3
- // (send one frame with 16 Bits)
- if(corr_i_cnt[5:2] == 4'b0000)
- ssp_frame = 1'b1;
- else
- ssp_frame = 1'b0;
-
-end
-
-assign ssp_din = corr_i_out[7];
-
-assign dbg = corr_i_cnt[3];
-
-endmodule
projects / proxmark3-svn / blobdiff