This version code now reads a TI tag properly.

[proxmark3-svn] / fpga / lo_passthru.v

diff --git a/fpga/lo_passthru.v b/fpga/lo_passthru.v
index 381426953888f0c0f409e3b707206c07496ea2fd..e1cb2ef23f4527a72997fbf4949a7bca523e6989 100644 (file)
--- a/fpga/lo_passthru.v
+++ b/fpga/lo_passthru.v
@@ -9,7 +9,7 @@ module lo_passthru(
     adc_d, adc_clk,\r
     ssp_frame, ssp_din, ssp_dout, ssp_clk,\r
     cross_hi, cross_lo,\r
-    dbg\r
+    dbg, divisor\r
 );\r
     input pck0, ck_1356meg, ck_1356megb;\r
     output pwr_lo, pwr_hi, pwr_oe1, pwr_oe2, pwr_oe3, pwr_oe4;\r
@@ -19,14 +19,35 @@ module lo_passthru(
     output ssp_frame, ssp_din, ssp_clk;\r
     input cross_hi, cross_lo;\r
     output dbg;\r
+    input [7:0] divisor;\r
 \r
-// No logic, straight through.\r
+reg [7:0] pck_divider;\r
+reg ant_lo;\r
 \r
+// this task runs on the rising egde of pck0 clock (24Mhz) and creates ant_lo\r
+// which is high for (divisor+1) pck0 cycles and low for the same duration\r
+// ant_lo is therefore a 50% duty cycle clock signal with a frequency of\r
+// 12Mhz/(divisor+1) which drives the antenna as well as the ADC clock adc_clk\r
+always @(posedge pck0)\r
+begin\r
+       if(pck_divider == divisor[7:0])\r
+               begin\r
+                       pck_divider <= 8'd0;\r
+                       ant_lo = !ant_lo;\r
+               end\r
+       else\r
+       begin\r
+               pck_divider <= pck_divider + 1;\r
+       end\r
+end\r
+\r
+// the antenna is modulated when ssp_dout = 1, when 0 the\r
+// antenna drivers stop modulating and go into listen mode\r
 assign pwr_oe3 = 1'b0;\r
-assign pwr_oe1 = 1'b1;\r
-assign pwr_oe2 = 1'b1;\r
-assign pwr_oe4 = 1'b1;\r
-assign pwr_lo = 1'b0;\r
+assign pwr_oe1 = ssp_dout;\r
+assign pwr_oe2 = ssp_dout;\r
+assign pwr_oe4 = ssp_dout;\r
+assign pwr_lo = ant_lo && ssp_dout;\r
 assign pwr_hi = 1'b0;\r
 assign adc_clk = 1'b0;\r
 assign ssp_din = cross_lo;\r