THIS REQUIRES A BOOTROM UPDATE!! To save FPGA area, split the LF and HF bitstreams and load them on-demand.

fpga/fpga_lf.v

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+//-----------------------------------------------------------------------------
+// The FPGA is responsible for interfacing between the A/D, the coil drivers,
+// and the ARM. In the low-frequency modes it passes the data straight
+// through, so that the ARM gets raw A/D samples over the SSP. In the high-
+// frequency modes, the FPGA might perform some demodulation first, to
+// reduce the amount of data that we must send to the ARM.
+//
+// I am not really an FPGA/ASIC designer, so I am sure that a lot of this
+// could be improved.
+//
+// Jonathan Westhues, March 2006
+// Added ISO14443-A support by Gerhard de Koning Gans, April 2008
+//-----------------------------------------------------------------------------
+
+`include "lo_read.v"
+`include "lo_passthru.v"
+`include "lo_edge_detect.v"
+`include "util.v"
+`include "clk_divider.v"
+
+module fpga_lf(
+	input spck, output miso, input mosi, input ncs,
+	input pck0, input ck_1356meg, input ck_1356megb,
+	output pwr_lo, output pwr_hi,
+	output pwr_oe1, output pwr_oe2, output pwr_oe3, output pwr_oe4,
+	input [7:0] adc_d, output adc_clk, output adc_noe,
+	output ssp_frame, output ssp_din, input ssp_dout, output ssp_clk,
+	input cross_hi, input cross_lo,
+	output dbg
+);
+
+//-----------------------------------------------------------------------------
+// The SPI receiver. This sets up the configuration word, which the rest of
+// the logic looks at to determine how to connect the A/D and the coil
+// drivers (i.e., which section gets it). Also assign some symbolic names
+// to the configuration bits, for use below.
+//-----------------------------------------------------------------------------
+
+reg [15:0] shift_reg;
+reg [7:0] divisor;
+reg [7:0] conf_word;
+
+// We switch modes between transmitting to the 13.56 MHz tag and receiving
+// from it, which means that we must make sure that we can do so without
+// glitching, or else we will glitch the transmitted carrier.
+always @(posedge ncs)
+begin
+	case(shift_reg[15:12])
+		4'b0001: conf_word <= shift_reg[7:0];		// FPGA_CMD_SET_CONFREG
+		4'b0010: divisor <= shift_reg[7:0];		// FPGA_CMD_SET_DIVISOR
+	endcase
+end
+
+always @(posedge spck)
+begin
+	if(~ncs)
+	begin
+		shift_reg[15:1] <= shift_reg[14:0];
+		shift_reg[0] <= mosi;
+	end
+end
+
+wire [2:0] major_mode;
+assign major_mode = conf_word[7:5];
+
+// For the low-frequency configuration:
+wire lf_field = conf_word[0];
+
+//-----------------------------------------------------------------------------
+// And then we instantiate the modules corresponding to each of the FPGA's
+// major modes, and use muxes to connect the outputs of the active mode to
+// the output pins.
+//-----------------------------------------------------------------------------
+wire [7:0] pck_cnt;
+wire pck_divclk;
+clk_divider div_clk(pck0, divisor, pck_cnt, pck_divclk);
+
+lo_read lr(
+	pck0, pck_cnt, pck_divclk,
+	lr_pwr_lo, lr_pwr_hi, lr_pwr_oe1, lr_pwr_oe2, lr_pwr_oe3, lr_pwr_oe4,
+	adc_d, lr_adc_clk,
+	lr_ssp_frame, lr_ssp_din, lr_ssp_clk,
+	lr_dbg
+);
+
+lo_passthru lp(
+	pck_divclk,
+	lp_pwr_lo, lp_pwr_hi, lp_pwr_oe1, lp_pwr_oe2, lp_pwr_oe3, lp_pwr_oe4,
+	lp_adc_clk,
+	lp_ssp_din, ssp_dout,
+	cross_lo,
+	lp_dbg
+);
+
+lo_edge_detect le(
+	pck0, pck_cnt, pck_divclk,
+	le_pwr_lo, le_pwr_hi, le_pwr_oe1, le_pwr_oe2, le_pwr_oe3, le_pwr_oe4,
+	adc_d, le_adc_clk,
+	le_ssp_frame, ssp_dout, le_ssp_clk,
+	cross_lo,
+	le_dbg,
+	lf_field
+);
+
+// Major modes:
+//   000 --  LF reader (generic)
+//   001 --  LF edge detect (generic)
+//   010 --  LF passthrough
+
+mux8 mux_ssp_clk		(major_mode, ssp_clk,   lr_ssp_clk,   le_ssp_clk,         1'b0,   1'b0, 1'b0, 1'b0, 1'b0, 1'b0);
+mux8 mux_ssp_din		(major_mode, ssp_din,   lr_ssp_din,         1'b0,         1'b0,   1'b0, 1'b0, 1'b0, 1'b0, 1'b0);
+mux8 mux_ssp_frame		(major_mode, ssp_frame, lr_ssp_frame, le_ssp_frame,       1'b0,   1'b0, 1'b0, 1'b0, 1'b0, 1'b0); 
+mux8 mux_pwr_oe1		(major_mode, pwr_oe1,   lr_pwr_oe1,   le_pwr_oe1,   lp_pwr_oe1,   1'b0, 1'b0, 1'b0, 1'b0, 1'b0);
+mux8 mux_pwr_oe2		(major_mode, pwr_oe2,   lr_pwr_oe2,   le_pwr_oe2,   lp_pwr_oe2,   1'b0, 1'b0, 1'b0, 1'b0, 1'b0); 
+mux8 mux_pwr_oe3		(major_mode, pwr_oe3,   lr_pwr_oe3,   le_pwr_oe3,   lp_pwr_oe3,   1'b0, 1'b0, 1'b0, 1'b0, 1'b0);
+mux8 mux_pwr_oe4		(major_mode, pwr_oe4,   lr_pwr_oe4,   le_pwr_oe4,   lp_pwr_oe4,   1'b0, 1'b0, 1'b0, 1'b0, 1'b0); 
+mux8 mux_pwr_lo			(major_mode, pwr_lo,    lr_pwr_lo,    le_pwr_lo,    lp_pwr_lo,    1'b0, 1'b0, 1'b0, 1'b0, 1'b0); 
+mux8 mux_pwr_hi			(major_mode, pwr_hi,    lr_pwr_hi,    le_pwr_hi,    lp_pwr_hi,    1'b0, 1'b0, 1'b0, 1'b0, 1'b0); 
+mux8 mux_adc_clk		(major_mode, adc_clk,   lr_adc_clk,   le_adc_clk,   lp_adc_clk,   1'b0, 1'b0, 1'b0, 1'b0, 1'b0); 
+mux8 mux_dbg			(major_mode, dbg,       lr_dbg,       le_dbg,       lp_dbg,       1'b0, 1'b0, 1'b0, 1'b0, 1'b0); 
+
+// In all modes, let the ADC's outputs be enabled.
+assign adc_noe = 1'b0;
+
+endmodule