ADD: @marshmello42 's fixes for low frequency demodulation lengths greater the 512bits.

[proxmark3-svn] / fpga / hi_read_rx_xcorr.v

diff --git a/fpga/hi_read_rx_xcorr.v b/fpga/hi_read_rx_xcorr.v
index a6a99cd574b97e2a7a2b253df5becddf1b4fbeb6..afaf7cb6fb17ae0a1f5687a9b48601ead3d65c23 100644 (file)
--- 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,
-    snoop
+    xcorr_is_848, snoop
 );
     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 snoop;
+    input xcorr_is_848, snoop;
 
 // Carrier is steady on through this, unless we're snooping.
 assign pwr_hi = ck_1356megb & (~snoop);
@@ -30,6 +30,10 @@ assign pwr_oe4 = 1'b0;
 
 wire adc_clk = ck_1356megb;
 
+reg fc_div_2;
+always @(negedge ck_1356megb)
+    fc_div_2 <= fc_div_2 + 1;
+
 // 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.
@@ -71,20 +75,24 @@ reg ssp_clk;
 reg ssp_frame;
 
 
+always @(negedge adc_clk)
+begin
+       if (xcorr_is_848 | fc_div_2)
+               corr_i_cnt <= corr_i_cnt + 1;
+end            
+               
 
 // ADC data appears on the rising edge, so sample it on the falling edge
 always @(negedge adc_clk)
 begin
-    corr_i_cnt <= corr_i_cnt + 1;
-
     // 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'd0)
+    if(corr_i_cnt == 6'd0)
     begin
         if(snoop)
         begin
-                       // 7 most significant bits of tag signal (signed), 1 bit reader signal:
+                       // 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;
@@ -115,7 +123,7 @@ begin
 
     // 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)
+    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.