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   1 //-----------------------------------------------------------------------------
   2 // The FPGA is responsible for interfacing between the A/D, the coil drivers,
   3 // and the ARM. In the low-frequency modes it passes the data straight
   4 // through, so that the ARM gets raw A/D samples over the SSP. In the high-
   5 // frequency modes, the FPGA might perform some demodulation first, to
   6 // reduce the amount of data that we must send to the ARM.
   7 //
   8 // I am not really an FPGA/ASIC designer, so I am sure that a lot of this
   9 // could be improved.
  10 //
  11 // Jonathan Westhues, March 2006
  12 // iZsh <izsh at fail0verflow.com>, June 2014
  13 //-----------------------------------------------------------------------------
  14
  15 `include "lo_read.v"
  16 `include "lo_passthru.v"
  17 `include "lo_edge_detect.v"
  18 `include "util.v"
  19 `include "clk_divider.v"
  20
  21 module fpga_lf(
  22         input spck, output miso, input mosi, input ncs,
  23         input pck0, input ck_1356meg, input ck_1356megb,
  24         output pwr_lo, output pwr_hi,
  25         output pwr_oe1, output pwr_oe2, output pwr_oe3, output pwr_oe4,
  26         input [7:0] adc_d, output adc_clk, output adc_noe,
  27         output ssp_frame, output ssp_din, input ssp_dout, output ssp_clk,
  28         input cross_hi, input cross_lo,
  29         output dbg
  30 );
  31
  32 //-----------------------------------------------------------------------------
  33 // The SPI receiver. This sets up the configuration word, which the rest of
  34 // the logic looks at to determine how to connect the A/D and the coil
  35 // drivers (i.e., which section gets it). Also assign some symbolic names
  36 // to the configuration bits, for use below.
  37 //-----------------------------------------------------------------------------
  38
  39 reg [15:0] shift_reg;
  40 reg [7:0] divisor;
  41 reg [7:0] conf_word;
  42
  43 // We switch modes between transmitting to the 13.56 MHz tag and receiving
  44 // from it, which means that we must make sure that we can do so without
  45 // glitching, or else we will glitch the transmitted carrier.
  46 always @(posedge ncs)
  47 begin
  48         case(shift_reg[15:12])
  49                 4'b0001: conf_word <= shift_reg[7:0];           // FPGA_CMD_SET_CONFREG
  50                 4'b0010: divisor <= shift_reg[7:0];             // FPGA_CMD_SET_DIVISOR
  51         endcase
  52 end
  53
  54 always @(posedge spck)
  55 begin
  56         if(~ncs)
  57         begin
  58                 shift_reg[15:1] <= shift_reg[14:0];
  59                 shift_reg[0] <= mosi;
  60         end
  61 end
  62
  63 wire [2:0] major_mode;
  64 assign major_mode = conf_word[7:5];
  65
  66 // For the low-frequency configuration:
  67 wire lf_field = conf_word[0];
  68
  69 //-----------------------------------------------------------------------------
  70 // And then we instantiate the modules corresponding to each of the FPGA's
  71 // major modes, and use muxes to connect the outputs of the active mode to
  72 // the output pins.
  73 //-----------------------------------------------------------------------------
  74 wire [7:0] pck_cnt;
  75 wire pck_divclk;
  76 clk_divider div_clk(pck0, divisor, pck_cnt, pck_divclk);
  77
  78 lo_read lr(
  79         pck0, pck_cnt, pck_divclk,
  80         lr_pwr_lo, lr_pwr_hi, lr_pwr_oe1, lr_pwr_oe2, lr_pwr_oe3, lr_pwr_oe4,
  81         adc_d, lr_adc_clk,
  82         lr_ssp_frame, lr_ssp_din, lr_ssp_clk,
  83         lr_dbg, lf_field
  84 );
  85
  86 lo_passthru lp(
  87         pck_divclk,
  88         lp_pwr_lo, lp_pwr_hi, lp_pwr_oe1, lp_pwr_oe2, lp_pwr_oe3, lp_pwr_oe4,
  89         lp_adc_clk,
  90         lp_ssp_din, ssp_dout,
  91         cross_lo,
  92         lp_dbg
  93 );
  94
  95 lo_edge_detect le(
  96         pck0, pck_cnt, pck_divclk,
  97         le_pwr_lo, le_pwr_hi, le_pwr_oe1, le_pwr_oe2, le_pwr_oe3, le_pwr_oe4,
  98         adc_d, le_adc_clk,
  99         le_ssp_frame, ssp_dout, le_ssp_clk,
 100         cross_lo,
 101         le_dbg,
 102         lf_field
 103 );
 104
 105 // Major modes:
 106 //   000 --  LF reader (generic)
 107 //   001 --  LF edge detect (generic)
 108 //   010 --  LF passthrough
 109
 110 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);
 111 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);
 112 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);
 113 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);
 114 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);
 115 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);
 116 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);
 117 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);
 118 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);
 119 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);
 120 mux8 mux_dbg                    (major_mode, dbg,       lr_dbg,       le_dbg,       lp_dbg,       1'b0, 1'b0, 1'b0, 1'b0, 1'b0);
 121
 122 // In all modes, let the ADC's outputs be enabled.
 123 assign adc_noe = 1'b0;
 124
 125 endmodule