X-Git-Url: http://git.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/c7b2751136b82bb3c0c61b49cc8cb4008a65d8dd..45eb1383e3029d887549161b4125f33550c23de6:/fpga/hi_read_rx_xcorr.v diff --git a/fpga/hi_read_rx_xcorr.v b/fpga/hi_read_rx_xcorr.v index 80e36327..433d6736 100644 --- a/fpga/hi_read_rx_xcorr.v +++ b/fpga/hi_read_rx_xcorr.v @@ -10,7 +10,7 @@ module hi_read_rx_xcorr( ssp_frame, ssp_din, ssp_dout, ssp_clk, cross_hi, cross_lo, dbg, - xcorr_is_848, snoop + 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; @@ -20,7 +20,7 @@ module hi_read_rx_xcorr( output ssp_frame, ssp_din, ssp_clk; input cross_hi, cross_lo; output dbg; - input xcorr_is_848, snoop; + input xcorr_is_848, snoop, xcorr_quarter_freq; // Carrier is steady on through this, unless we're snooping. assign pwr_hi = ck_1356megb & (~snoop); @@ -28,19 +28,21 @@ assign pwr_oe1 = 1'b0; assign pwr_oe3 = 1'b0; assign pwr_oe4 = 1'b0; -// Clock divider -reg [0:0] fc_divider; +reg [2:0] fc_div; always @(negedge ck_1356megb) - fc_divider <= fc_divider + 1; -wire fc_div2 = fc_divider[0]; + fc_div <= fc_div + 1; -reg adc_clk; -always @(ck_1356megb) - if (xcorr_is_848) +(* 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, standard ISO14443B adc_clk <= ck_1356megb; - else - adc_clk <= fc_div2; - + else if (~xcorr_is_848 & ~xcorr_quarter_freq) // fc = 423.75 kHz + adc_clk <= fc_div[0]; + else if (xcorr_is_848 & xcorr_quarter_freq) // fc = 211.875 kHz + adc_clk <= fc_div[1]; + else // fc = 105.9375 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. @@ -67,14 +69,16 @@ begin end end -// Let us report a correlation every 4 subcarrier cycles, or 4*16 samples, +// Let us report a correlation every 4 subcarrier cycles, or 4*16=64 samples, // so we need a 6-bit counter. reg [5:0] corr_i_cnt; // And a couple of registers in which to accumulate the correlations. -// we would add at most 32 times adc_d, the result can be held in 13 bits. -// Need one additional bit because it can be negative as well -reg signed [13:0] corr_i_accum; -reg signed [13:0] corr_q_accum; +// 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. +reg signed [11:0] corr_i_accum; +reg signed [11:0] 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 @@ -84,7 +88,7 @@ reg ssp_frame; always @(negedge adc_clk) begin - corr_i_cnt <= corr_i_cnt + 1; + corr_i_cnt <= corr_i_cnt + 1; end @@ -98,16 +102,16 @@ begin 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}; + // Send 7 most significant bits of tag signal (signed), plus 1 bit reader signal + corr_i_out <= {corr_i_accum[11:5], after_hysteresis_prev_prev}; + corr_q_out <= {corr_q_accum[11:5], after_hysteresis_prev}; after_hysteresis_prev_prev <= after_hysteresis; 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]; + // 8 bits of tag signal + corr_i_out <= corr_i_accum[11:4]; + corr_q_out <= corr_q_accum[11:4]; end corr_i_accum <= adc_d;