MAJOR update, added hitag2 reader, emulation and eavesdropping, lots of new code, including FPGA tweaks, part 2

fpga/lo_edge_detect.v

@@ -0,0 +1,90 @@
+//-----------------------------------------------------------------------------
+// The way that we connect things in low-frequency simulation mode. In this
+// case just pass everything through to the ARM, which can bit-bang this
+// (because it is so slow).
+//
+// Jonathan Westhues, April 2006
+//-----------------------------------------------------------------------------
+
+module lo_edge_detect(
+    pck0, ck_1356meg, ck_1356megb,
+    pwr_lo, pwr_hi, pwr_oe1, pwr_oe2, pwr_oe3, pwr_oe4,
+    adc_d, adc_clk,
+    ssp_frame, ssp_din, ssp_dout, ssp_clk,
+    cross_hi, cross_lo,
+    dbg,
+	  divisor,
+		lf_field
+);
+    input pck0, ck_1356meg, ck_1356megb;
+    output pwr_lo, pwr_hi, pwr_oe1, pwr_oe2, pwr_oe3, pwr_oe4;
+    input [7:0] adc_d;
+    output adc_clk;
+    input ssp_dout;
+    output ssp_frame, ssp_din, ssp_clk;
+    input cross_hi, cross_lo;
+    output dbg;
+	  input [7:0] divisor;
+		input lf_field;
+
+// Divide the clock to be used for the ADC
+reg [7:0] pck_divider;
+reg clk_state;
+
+wire tag_modulation; 
+assign tag_modulation = ssp_dout & !lf_field;
+wire reader_modulation; 
+assign reader_modulation = !ssp_dout & lf_field & clk_state;
+
+// No logic, straight through.
+assign pwr_oe1 = 1'b0; // not used in LF mode
+assign pwr_oe2 = tag_modulation;
+assign pwr_oe3 = tag_modulation;
+assign pwr_oe4 = tag_modulation;
+assign ssp_clk = cross_lo;
+assign pwr_lo = reader_modulation;
+assign pwr_hi = 1'b0;
+assign dbg = ssp_frame;
+
+always @(posedge pck0)
+begin
+	if(pck_divider == divisor[7:0])
+		begin
+			pck_divider <= 8'd0;
+			clk_state = !clk_state;
+		end
+	else
+	begin
+		pck_divider <= pck_divider + 1;
+	end
+end
+
+assign adc_clk = ~clk_state;
+
+// Toggle the output with hysteresis
+//  Set to high if the ADC value is above 200
+//  Set to low if the ADC value is below 64
+reg is_high;
+reg is_low;
+reg output_state;
+
+always @(posedge pck0)
+begin
+	if((pck_divider == 8'd7) && !clk_state) begin
+		is_high = (adc_d >= 8'd190);
+		is_low = (adc_d <= 8'd70);
+	end
+end
+
+always @(posedge is_high or posedge is_low)
+begin
+	if(is_high)
+		output_state <= 1'd1;
+	else if(is_low)
+		output_state <= 1'd0;
+end
+
+assign ssp_frame = output_state;
+
+endmodule
+