//-----------------------------------------------------------------------------
-// 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
// iZsh <izsh at fail0verflow.com>, June 2014
//-----------------------------------------------------------------------------
reg [15:0] shift_reg;
reg [7:0] divisor;
reg [7:0] conf_word;
+reg [7:0] user_byte1;
-// 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
+ 4'b0001:
+ begin
+ conf_word <= shift_reg[7:0];
+ if (shift_reg[7:0] == 8'b00000001) begin // LF edge detect
+ user_byte1 <= 127; // default threshold
+ end
+ end
+ 4'b0010: divisor <= shift_reg[7:0]; // FPGA_CMD_SET_DIVISOR
+ 4'b0011: user_byte1 <= shift_reg[7:0]; // FPGA_CMD_SET_USER_BYTE1
endcase
end
end
end
-wire [2:0] major_mode;
-assign major_mode = conf_word[7:5];
+wire [2:0] major_mode = conf_word[7:5];
// For the low-frequency configuration:
wire lf_field = conf_word[0];
+wire lf_ed_toggle_mode = conf_word[1]; // for lo_edge_detect
+wire [7:0] lf_ed_threshold = user_byte1;
//-----------------------------------------------------------------------------
// And then we instantiate the modules corresponding to each of the FPGA's
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
+ lr_dbg, lf_field
);
lo_passthru lp(
);
lo_edge_detect le(
- pck0, pck_cnt, pck_divclk,
+ pck0, 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
+ lf_field,
+ lf_ed_toggle_mode, lf_ed_threshold
);
// Major modes:
// 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_din (major_mode, ssp_din, lr_ssp_din, 1'b0, lp_ssp_din, 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);