Potential fix for 0-length usb packets seen on OSX

[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 4a5de5536c64cffc2233db2d77ab9bc433672d10..afaf7cb6fb17ae0a1f5687a9b48601ead3d65c23 100644 (file)
--- a/fpga/hi_read_rx_xcorr.v
+++ b/fpga/hi_read_rx_xcorr.v
@@ -28,22 +28,12 @@ assign pwr_oe1 = 1'b0;
 assign pwr_oe3 = 1'b0;
 assign pwr_oe4 = 1'b0;
 
-(* clock_signal = "yes" *) reg fc_div_2;
+wire adc_clk = ck_1356megb;
+
+reg fc_div_2;
 always @(negedge ck_1356megb)
     fc_div_2 <= fc_div_2 + 1;
 
-(* clock_signal = "yes" *) reg adc_clk;
-always @(xcorr_is_848, ck_1356megb, fc_div_2)
-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_1356megb;
-else
-    // The subcarrier frequency is fc/32; we will sample at fc/2, and
-    // the subcarrier will look identical.
-    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.
@@ -85,20 +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;
@@ -129,7 +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.