ssp_frame, ssp_din, ssp_dout, ssp_clk,
cross_hi, cross_lo,
dbg,
- xcorr_is_848, snoop, xcorr_quarter_freq
+ 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;
output ssp_frame, ssp_din, ssp_clk;
input cross_hi, cross_lo;
output dbg;
- input xcorr_is_848, snoop, xcorr_quarter_freq;
+ 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
-reg [2:0] fc_div;
-always @(negedge ck_1356megb)
- fc_div <= fc_div + 1;
-
-(* clock_signal = "yes" *) reg adc_clk; // sample frequency, always 16 * fc
-always @(ck_1356megb, xcorr_is_848, xcorr_quarter_freq, fc_div)
- if (xcorr_is_848 & ~xcorr_quarter_freq) // fc = 847.5 kHz
- adc_clk <= ck_1356megb;
- else if (~xcorr_is_848 & ~xcorr_quarter_freq) // fc = 424.25 kHz
- adc_clk <= fc_div[0];
- else if (xcorr_is_848 & xcorr_quarter_freq) // fc = 212.125 kHz
- adc_clk <= fc_div[1];
- else // fc = 106.0625 kHz
- adc_clk <= fc_div[2];
-
// 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.
end
end
-// Let us report a correlation every 4 subcarrier cycles, or 4*16 samples,
-// so we need a 6-bit counter.
+
+// 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;
-// And a couple of registers in which to accumulate the correlations.
-// we would add/sub at most 32 times adc_d, the signed result can be held in 14 bits.
+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;
-always @(negedge adc_clk)
+
+// 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
- corr_i_cnt <= corr_i_cnt + 1;
-end
-
+ 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) result to
- // send out later over the SSP.
+ // 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
- // Send only 7 most significant bits of tag signal (signed), LSB is reader signal:
- corr_i_out <= {corr_i_accum[13:7], after_hysteresis_prev_prev};
- corr_q_out <= {corr_q_accum[13:7], after_hysteresis_prev};
- after_hysteresis_prev_prev <= after_hysteresis;
+ 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
- // 8 most significant bits of tag signal
- corr_i_out <= corr_i_accum[13:6];
- corr_q_out <= corr_q_accum[13:6];
+ 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
- corr_i_accum <= adc_d;
- corr_q_accum <= adc_d;
+ // 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(corr_i_cnt[3])
- corr_i_accum <= corr_i_accum - adc_d;
+ if (subcarrier_I)
+ corr_i_accum <= corr_i_accum + $signed({1'b0,adc_d});
else
- corr_i_accum <= corr_i_accum + adc_d;
+ corr_i_accum <= corr_i_accum - $signed({1'b0,adc_d});
- if(corr_i_cnt[3] == corr_i_cnt[2]) // phase shifted by pi/2
- corr_q_accum <= corr_q_accum + adc_d;
+ if (subcarrier_Q)
+ corr_q_accum <= corr_q_accum + $signed({1'b0,adc_d});
else
- corr_q_accum <= corr_q_accum - adc_d;
-
+ corr_q_accum <= corr_q_accum - $signed({1'b0,adc_d});
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.
+ // 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 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;
end
end
- // set ssp_frame signal for corr_i_cnt = 0..3 and corr_i_cnt = 32..35
- // (send two frames with 8 Bits each)
- if(corr_i_cnt[5:2] == 4'b0000 || corr_i_cnt[5:2] == 4'b1000)
+ // 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;
assign dbg = corr_i_cnt[3];
-// Unused.
-assign pwr_lo = 1'b0;
-assign pwr_oe2 = 1'b0;
-
endmodule
projects / proxmark3-svn / blobdiff