// Gerhard de Koning Gans, April 2008
//-----------------------------------------------------------------------------
+// constants for the different modes:
+`define SNIFFER 3'b000
+`define TAGSIM_LISTEN 3'b001
+`define TAGSIM_MOD 3'b010
+`define READER_LISTEN 3'b011
+`define READER_MOD 3'b100
+
module hi_iso14443a(
pck0, ck_1356meg, ck_1356megb,
pwr_lo, pwr_hi, pwr_oe1, pwr_oe2, pwr_oe3, pwr_oe4,
reg ssp_clk;
reg ssp_frame;
-reg fc_div_2;
-always @(posedge ck_1356meg)
- fc_div_2 = ~fc_div_2;
-
wire adc_clk;
assign adc_clk = ck_1356meg;
-reg after_hysteresis, after_hysteresis_prev1, after_hysteresis_prev2, after_hysteresis_prev3;
+reg after_hysteresis, after_hysteresis_prev1, after_hysteresis_prev2, after_hysteresis_prev3, after_hysteresis_prev4;
reg [11:0] has_been_low_for;
reg [8:0] saw_deep_modulation;
reg [2:0] deep_counter;
reg deep_modulation;
+
always @(negedge adc_clk)
begin
- if(& adc_d[7:6]) after_hysteresis <= 1'b1;
- else if(~(| adc_d[7:4])) after_hysteresis <= 1'b0;
+ if(& adc_d[7:6]) after_hysteresis <= 1'b1; // adc_d >= 196 (U >= 3,28V) -> after_hysteris = 1
+ else if(~(| adc_d[7:4])) after_hysteresis <= 1'b0; // if adc_d <= 15 (U <= 1,13V) -> after_hysteresis = 0
- if(~(| adc_d[7:0]))
+ if(~(| adc_d[7:0])) // if adc_d == 0 (U <= 0,94V)
begin
- if(deep_counter == 3'd7)
+ if(deep_counter == 3'd7) // adc_d == 0 for 7 adc_clk ticks -> deep_modulation (by reader)
begin
deep_modulation <= 1'b1;
saw_deep_modulation <= 8'd0;
else
deep_counter <= deep_counter + 1;
end
- else
+ else
begin
deep_counter <= 3'd0;
- if(saw_deep_modulation == 8'd255)
+ if(saw_deep_modulation == 8'd255) // adc_d != 0 for 255 adc_clk ticks -> deep_modulation is over, now waiting for tag's response
deep_modulation <= 1'b0;
else
saw_deep_modulation <= saw_deep_modulation + 1;
if(after_hysteresis)
begin
- has_been_low_for <= 7'b0;
+ has_been_low_for <= 12'd0;
end
else
begin
if(has_been_low_for == 12'd4095)
begin
has_been_low_for <= 12'd0;
- after_hysteresis <= 1'b1;
+ after_hysteresis <= 1'b1; // reset after_hysteresis to 1 if it had been 0 for 4096 cycles (no field)
end
else
+ begin
has_been_low_for <= has_been_low_for + 1;
+ end
end
end
+
+
// Report every 4 subcarrier cycles
-// 64 periods of carrier frequency => 6-bit counter [negedge_cnt]
-reg [5:0] negedge_cnt;
-reg bit1, bit2, bit3;
-reg [3:0] count_ones;
-reg [3:0] count_zeros;
-wire [7:0] avg;
-reg [7:0] lavg;
-reg signed [12:0] step1;
-reg signed [12:0] step2;
-reg [7:0] stepsize;
+// 128 periods of carrier frequency => 7-bit counter [negedge_cnt]
+reg [6:0] negedge_cnt;
+reg bit1, bit2, bit3, bit4;
reg curbit;
-reg [12:0] average;
-wire signed [9:0] dif;
-// A register to send the results to the arm
-reg signed [7:0] to_arm;
+// storage for four previous samples:
+reg [7:0] adc_d_1;
+reg [7:0] adc_d_2;
+reg [7:0] adc_d_3;
+reg [7:0] adc_d_4;
+
+// the filtered signal (filter performs noise reduction and edge detection)
+// (gaussian derivative)
+wire signed [10:0] adc_d_filtered;
+assign adc_d_filtered = (adc_d_4 << 1) + adc_d_3 - adc_d_1 - (adc_d << 1);
+
+// Registers to store steepest edges detected:
+reg [7:0] rx_mod_falling_edge_max;
+reg [7:0] rx_mod_rising_edge_max;
+
+// A register to send 8 Bit results to the arm
+reg [7:0] to_arm;
-assign avg[7:0] = average[11:4];
-assign dif = lavg - avg;
reg bit_to_arm;
reg fdt_indicator, fdt_elapsed;
reg [10:0] fdt_counter;
-reg [47:0] mod_sig_buf;
-wire mod_sig_buf_empty;
-reg [5:0] mod_sig_ptr;
+//reg [47:0] mod_sig_buf;
+reg [31:0] mod_sig_buf;
+//reg [5:0] mod_sig_ptr;
+reg [4:0] mod_sig_ptr;
reg [3:0] mod_sig_flip;
reg mod_sig, mod_sig_coil;
reg temp_buffer_reset;
reg sendbit;
-
-assign mod_sig_buf_empty = ~(|mod_sig_buf[47:0]);
-reg [2:0] ssp_frame_counter;
+reg [3:0] sub_carrier_cnt;
// ADC data appears on the rising edge, so sample it on the falling edge
always @(negedge adc_clk)
begin
-
- // last bit = 0 then fdt = 1172, in case of 0x26 (7-bit command, LSB first!)
- // last bit = 1 then fdt = 1236, in case of 0x52 (7-bit command, LSB first!)
- if(fdt_counter == 11'd740) fdt_indicator = 1'b1;
+ // ------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ // relevant for TAGSIM_MOD only. Timing of Tag's answer relative to a command received from a reader
+ // ISO14443-3 specifies:
+ // fdt = 1172, if last bit was 0.
+ // fdt = 1236, if last bit was 1.
+ // the FPGA takes care for the 1172 delay. To achieve the additional 1236-1172=64 ticks delay, the ARM must send an additional correction bit (before the start bit).
+ // The correction bit will be coded as 00010000, i.e. it adds 4 bits to the transmission stream, causing the required delay.
+ if(fdt_counter == 11'd547) fdt_indicator <= 1'b1; // The ARM must not send earlier to prevent mod_sig_buf overflow.
+ // The mod_sig_buf can buffer 29 excess data bits, i.e. a maximum delay of 29 * 16 = 464 adc_clk ticks. fdt_indicator
+ // could appear at ssp_din after 1 tick, 16 ticks for the transfer, 128 ticks until response is sended.
+ // 1148 - 464 - 1 - 128 - 8 = 547
- if(fdt_counter == 11'd1148)
+ if ((mod_type == `TAGSIM_MOD) || (mod_type == `TAGSIM_LISTEN))
begin
- if(fdt_elapsed)
+ if(fdt_counter == 11'd1148) // the RF part delays the rising edge by approx 5 adc_clk_ticks, the ADC needs 3 clk_ticks for A/D conversion,
+ // 16 ticks delay by mod_sig_buf
+ // 1172 - 5 - 3 - 16 = 1148.
begin
- if(negedge_cnt[3:0] == mod_sig_flip[3:0]) mod_sig_coil <= mod_sig;
+ if(fdt_elapsed)
+ begin
+ if(negedge_cnt[3:0] == mod_sig_flip) mod_sig_coil <= mod_sig; // start modulating (if mod_sig is already set)
+ sub_carrier_cnt[3:0] <= sub_carrier_cnt[3:0] + 1;
+ end
+ else
+ begin
+ mod_sig_flip <= negedge_cnt[3:0]; // start modulation at this time
+ sub_carrier_cnt[3:0] <= 0; // subcarrier phase in sync with start of modulation
+ mod_sig_coil <= mod_sig; // assign signal to coil
+ fdt_elapsed = 1'b1;
+ if(~(| mod_sig_ptr[4:0])) mod_sig_ptr <= 5'd9; // if mod_sig_ptr == 0 -> didn't receive a 1 yet. Delay next 1 by n*128 ticks.
+ else temp_buffer_reset = 1'b1; // else fix the buffer size at current position
+ end
end
else
begin
- mod_sig_flip[3:0] <= negedge_cnt[3:0];
- mod_sig_coil <= mod_sig;
- fdt_elapsed = 1'b1;
- fdt_indicator = 1'b0;
-
- if(~(| mod_sig_ptr[5:0])) mod_sig_ptr <= 6'b001001;
- else temp_buffer_reset = 1'b1; // fix position of the buffer pointer
+ fdt_counter <= fdt_counter + 1; // Count until 1155
end
end
- else
+ else // other modes: don't use the delay line.
begin
- fdt_counter <= fdt_counter + 1;
- end
+ mod_sig_coil <= ssp_dout;
+ end
- if(& negedge_cnt[3:0])
+
+ //-------------------------------------------------------------------------------------------------------------------------------------------
+ // Relevant for READER_LISTEN only
+ // look for steepest falling and rising edges:
+
+ if(negedge_cnt[3:0] == 4'd1) // reset modulation detector. Save current edge.
begin
- // When there is a dip in the signal and not in reader mode
- if(~after_hysteresis && mod_sig_buf_empty && ~((mod_type == 3'b100) || (mod_type == 3'b011) || (mod_type == 3'b010))) // last condition to prevent reset
+ if (adc_d_filtered > 0)
+ begin
+ rx_mod_falling_edge_max <= adc_d_filtered;
+ rx_mod_rising_edge_max <= 0;
+ end
+ else
begin
- fdt_counter <= 11'd0;
- fdt_elapsed = 1'b0;
- fdt_indicator = 1'b0;
- temp_buffer_reset = 1'b0;
- mod_sig_ptr <= 6'b000000;
+ rx_mod_falling_edge_max <= 0;
+ rx_mod_rising_edge_max <= -adc_d_filtered;
end
-
- lavg <= avg;
-
- if(stepsize<16) stepsize = 8'd16;
-
- if(dif>0)
+ end
+ else // detect modulation
+ begin
+ if (adc_d_filtered > 0)
begin
- step1 = dif*3;
- step2 = stepsize*2; // 3:2
- if(step1>step2)
- begin
- curbit = 1'b0;
- stepsize = dif;
- end
+ if (adc_d_filtered > rx_mod_falling_edge_max)
+ rx_mod_falling_edge_max <= adc_d_filtered;
end
else
begin
- step1 = dif*3;
- step1 = -step1;
- step2 = stepsize*2;
- if(step1>step2)
- begin
- curbit = 1'b1;
- stepsize = -dif;
- end
+ if (-adc_d_filtered > rx_mod_rising_edge_max)
+ rx_mod_rising_edge_max <= -adc_d_filtered;
end
-
- if(curbit)
+ end
+
+ // detect modulation signal: if modulating, there must be a falling and a rising edge
+ if (rx_mod_falling_edge_max > 6 && rx_mod_rising_edge_max > 6)
+ curbit <= 1'b1; // modulation
+ else
+ curbit <= 1'b0; // no modulation
+
+
+ // store previous samples for filtering and edge detection:
+ adc_d_4 <= adc_d_3;
+ adc_d_3 <= adc_d_2;
+ adc_d_2 <= adc_d_1;
+ adc_d_1 <= adc_d;
+
+
+ // Relevant for TAGSIM_MOD only (timing the Tag's answer. See above)
+ // When we see end of a modulation and we are emulating a Tag, start fdt_counter.
+ // Reset fdt_counter when modulation is detected.
+ if(~after_hysteresis /* && mod_sig_buf_empty */ && mod_type == `TAGSIM_LISTEN)
+ begin
+ fdt_counter <= 11'd0;
+ fdt_elapsed = 1'b0;
+ fdt_indicator <= 1'b0;
+ temp_buffer_reset = 1'b0;
+ mod_sig_ptr <= 5'b00000;
+ mod_sig = 1'b0;
+ end
+
+
+ if(negedge_cnt[3:0] == 4'd1)
+ begin
+ // What do we communicate to the ARM
+ if(mod_type == `TAGSIM_LISTEN)
+ sendbit = after_hysteresis;
+ else if(mod_type == `TAGSIM_MOD)
+ /* if(fdt_counter > 11'd772) sendbit = mod_sig_coil; // huh?
+ else */
+ sendbit = fdt_indicator;
+ else if (mod_type == `READER_LISTEN)
+ sendbit = curbit;
+ else
+ sendbit = 1'b0;
+ end
+
+ //------------------------------------------------------------------------------------------------------------------------------------------
+ // Prepare 8 Bits to communicate to ARM
+
+ // in SNIFFER mode: 4 Bits data sniffed as Tag, 4 Bits data sniffed as Reader
+ if(mod_type == `SNIFFER)
+ begin
+ if (negedge_cnt == 7'd63)
begin
- count_zeros <= 4'd0;
- if(& count_ones[3:2])
+ if(deep_modulation) // a reader is sending (or there's no field at all)
begin
- curbit = 1'b0; // suppressed signal
- stepsize = 8'd24; // just a fine number
+ to_arm <= {after_hysteresis_prev1,after_hysteresis_prev2,after_hysteresis_prev3,after_hysteresis_prev4,1'b0,1'b0,1'b0,1'b0};
end
else
begin
- count_ones <= count_ones + 1;
+ to_arm <= {after_hysteresis_prev1,after_hysteresis_prev2,after_hysteresis_prev3,after_hysteresis_prev4,bit1,bit2,bit3,bit4};
end
+ negedge_cnt <= 0;
end
else
begin
- count_ones <= 4'd0;
- if(& count_zeros[3:0])
+ negedge_cnt <= negedge_cnt + 1;
+ end
+ end
+ else
+ // other modes: 8 Bits info on queue delay
+ begin
+ if(negedge_cnt == 7'd127)
+ begin
+ if (mod_type == `TAGSIM_MOD)
begin
- stepsize = 8'd24;
+ to_arm[7:0] <= {mod_sig_ptr[4:0], mod_sig_flip[3:1]};
end
else
begin
- count_zeros <= count_zeros + 1;
+ to_arm[7:0] <= 8'd0;
end
- end
-
- // What do we communicate to the ARM
- if(mod_type == 3'b001) sendbit = after_hysteresis;
- else if(mod_type == 3'b010)
- begin
- if(fdt_counter > 11'd772) sendbit = mod_sig_coil;
- else sendbit = fdt_indicator;
- end
- else if(mod_type == 3'b011) sendbit = curbit;
- else sendbit = 1'b0;
-
- end
-
- if(~(| negedge_cnt[3:0])) average <= adc_d;
- else average <= average + adc_d;
-
- if(negedge_cnt == 7'd63)
- begin
- if(deep_modulation)
- begin
- to_arm <= {after_hysteresis_prev1,after_hysteresis_prev2,after_hysteresis_prev3,after_hysteresis,1'b0,1'b0,1'b0,1'b0};
+ negedge_cnt <= 0;
end
else
begin
- to_arm <= {after_hysteresis_prev1,after_hysteresis_prev2,after_hysteresis_prev3,after_hysteresis,bit1,bit2,bit3,curbit};
+ negedge_cnt <= negedge_cnt + 1;
end
-
- negedge_cnt <= 0;
+ end
- end
- else
- begin
- negedge_cnt <= negedge_cnt + 1;
- end
-
- if(negedge_cnt == 6'd15)
+ if(negedge_cnt == 7'd1)
begin
after_hysteresis_prev1 <= after_hysteresis;
bit1 <= curbit;
end
- if(negedge_cnt == 6'd31)
+ if(negedge_cnt == 7'd17)
begin
after_hysteresis_prev2 <= after_hysteresis;
bit2 <= curbit;
end
- if(negedge_cnt == 6'd47)
+ if(negedge_cnt == 7'd33)
begin
after_hysteresis_prev3 <= after_hysteresis;
bit3 <= curbit;
end
+ if(negedge_cnt == 7'd47)
+ begin
+ after_hysteresis_prev4 <= after_hysteresis;
+ bit4 <= curbit;
+ end
-
- if(mod_type != 3'b000)
+ //--------------------------------------------------------------------------------------------------------------------------------------------------------------
+ // Relevant in TAGSIM_MOD only. Delay-Line to buffer data and send it at the correct time
+ if(negedge_cnt[3:0] == 4'd0) // at rising edge of ssp_clk - ssp_dout changes at the falling edge.
begin
- if(negedge_cnt[3:0] == 4'b1000)
+ mod_sig_buf[31:0] <= {mod_sig_buf[30:1], ssp_dout, 1'b0}; // shift in new data starting at mod_sig_buf[1]. mod_sig_buf[0] = 0 always.
+ // asign the delayed signal to mod_sig, but don't modulate with the correction bit (which is sent as 00010000, all other bits will come with at least 2 consecutive 1s)
+ // side effect: when ptr = 1 it will cancel the first 1 of every block of ones. Note: this would only be the case if we received a 1 just before fdt_elapsed.
+ if((ssp_dout || (| mod_sig_ptr[4:0])) && ~fdt_elapsed) // buffer a 1 (and all subsequent data) until fdt_counter = 1148 adc_clk ticks.
+ //if(mod_sig_ptr == 6'b101110) // buffer overflow at 46 - this would mean data loss
+ //begin
+ // mod_sig_ptr <= 6'b000000;
+ //end
+ if (mod_sig_ptr == 5'd30) mod_sig_ptr <= 5'd0;
+ else mod_sig_ptr <= mod_sig_ptr + 1; // increase buffer (= increase delay by 16 adc_clk ticks). ptr always points to first 1.
+ else if(fdt_elapsed && ~temp_buffer_reset)
+ // fdt_elapsed. If we didn't receive a 1 yet, ptr will be at 9 and not yet fixed. Otherwise temp_buffer_reset will be 1 already.
begin
- // The modulation signal of the tag
- mod_sig_buf[47:0] <= {mod_sig_buf[46:1], ssp_dout, 1'b0};
- if((ssp_dout || (| mod_sig_ptr[5:0])) && ~fdt_elapsed)
- if(mod_sig_ptr == 6'b101110)
- begin
- mod_sig_ptr <= 6'b000000;
- end
- else mod_sig_ptr <= mod_sig_ptr + 1;
- else if(fdt_elapsed && ~temp_buffer_reset)
- begin
- if(ssp_dout) temp_buffer_reset = 1'b1;
- if(mod_sig_ptr == 6'b000010) mod_sig_ptr <= 6'b001001;
- else mod_sig_ptr <= mod_sig_ptr - 1;
- end
- else
- begin
- // side effect: when ptr = 1 it will cancel the first 1 of every block of ones
- if(~mod_sig_buf[mod_sig_ptr-1] && ~mod_sig_buf[mod_sig_ptr+1]) mod_sig = 1'b0;
- else mod_sig = mod_sig_buf[mod_sig_ptr] & fdt_elapsed; // & fdt_elapsed was for direct relay to oe4
- end
+ // wait for the next 1 after fdt_elapsed before fixing the delay and starting modulation. This ensures that the response can only happen
+ // at intervals of 8 * 16 = 128 adc_clk ticks intervals (as defined in ISO14443-3)
+ if(ssp_dout) temp_buffer_reset = 1'b1;
+ if(mod_sig_ptr == 5'd2) mod_sig_ptr <= 5'd9; // still nothing received, need to go for the next interval
+ else mod_sig_ptr <= mod_sig_ptr - 1; // decrease buffer.
+ end
+ else
+ begin
+ if(~mod_sig_buf[mod_sig_ptr-1] && ~mod_sig_buf[mod_sig_ptr+1]) mod_sig = 1'b0;
+ // finally, assign the delayed signal:
+ else mod_sig = mod_sig_buf[mod_sig_ptr];
end
end
- // SSP Clock and data
- if(mod_type == 3'b000)
+ //-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ // Communication to ARM (SSP Clock and data)
+ // SNIFFER mode (ssp_clk = adc_clk / 8, ssp_frame clock = adc_clk / 64)):
+ if(mod_type == `SNIFFER)
begin
if(negedge_cnt[2:0] == 3'b100)
ssp_clk <= 1'b0;
begin
ssp_clk <= 1'b1;
// Don't shift if we just loaded new data, obviously.
- if(negedge_cnt != 7'd0)
+ if(negedge_cnt[5:0] != 6'd0)
begin
to_arm[7:1] <= to_arm[6:0];
end
bit_to_arm = to_arm[7];
end
else
+ //-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ // Communication to ARM (SSP Clock and data)
+ // all other modes (ssp_clk = adc_clk / 16, ssp_frame clock = adc_clk / 128):
begin
if(negedge_cnt[3:0] == 4'b1000) ssp_clk <= 1'b0;
if(negedge_cnt[3:0] == 4'b0111)
begin
- if(ssp_frame_counter == 3'd7) ssp_frame_counter <= 3'd0;
- else ssp_frame_counter <= ssp_frame_counter + 1;
+ // if(ssp_frame_counter == 3'd7) ssp_frame_counter <= 3'd0;
+ // else ssp_frame_counter <= ssp_frame_counter + 1;
+ if (negedge_cnt[6:4] == 3'b000) ssp_frame = 1'b1;
+ else ssp_frame = 1'b0;
end
+ // ssp_frame = (ssp_frame_counter == 3'd7);
if(negedge_cnt[3:0] == 4'b0000)
begin
ssp_clk <= 1'b1;
+ // Don't shift if we just loaded new data, obviously.
+ if(negedge_cnt[6:0] != 7'd0)
+ begin
+ to_arm[7:1] <= to_arm[6:0];
+ end
end
- ssp_frame = (ssp_frame_counter == 3'd7);
-
- bit_to_arm = sendbit;
- end
+ if (mod_type == `TAGSIM_MOD && fdt_elapsed && temp_buffer_reset)
+ // transmit timing information
+ bit_to_arm = to_arm[7];
+ else
+ // transmit data or fdt_indicator
+ bit_to_arm = sendbit;
+ end
-end
+end //always @(negedge adc_clk)
assign ssp_din = bit_to_arm;
-// Modulating carrier frequency is fc/16
-wire modulating_carrier;
-assign modulating_carrier = (mod_sig_coil & negedge_cnt[3] & (mod_type == 3'b010));
-assign pwr_hi = (ck_1356megb & (((mod_type == 3'b100) & ~mod_sig_coil) || (mod_type == 3'b011)));
-// This one is all LF, so doesn't matter
-//assign pwr_oe2 = modulating_carrier;
-assign pwr_oe2 = 1'b0;
+// Subcarrier (adc_clk/16, for TAGSIM_MOD only).
+wire sub_carrier;
+assign sub_carrier = ~sub_carrier_cnt[3];
-// Toggle only one of these, since we are already producing much deeper
-// modulation than a real tag would.
-//assign pwr_oe1 = modulating_carrier;
-assign pwr_oe1 = 1'b0;
-assign pwr_oe4 = modulating_carrier;
-//assign pwr_oe4 = 1'b0;
+// in READER_MOD: drop carrier for mod_sig_coil==1 (pause); in READER_LISTEN: carrier always on; in other modes: carrier always off
+assign pwr_hi = (ck_1356megb & (((mod_type == `READER_MOD) & ~mod_sig_coil) || (mod_type == `READER_LISTEN)));
-// This one is always on, so that we can watch the carrier.
-//assign pwr_oe3 = modulating_carrier;
-assign pwr_oe3 = 1'b0;
+// Enable HF antenna drivers:
+assign pwr_oe1 = 1'b0;
+assign pwr_oe3 = 1'b0;
-assign dbg = negedge_cnt[3];
+// TAGSIM_MOD: short circuit antenna with different resistances (modulated by sub_carrier modulated by mod_sig_coil)
+// for pwr_oe4 = 1 (tristate): antenna load = 10k || 33 = 32,9 Ohms
+// for pwr_oe4 = 0 (active): antenna load = 10k || 33 || 33 = 16,5 Ohms
+assign pwr_oe4 = ~(mod_sig_coil & sub_carrier & (mod_type == `TAGSIM_MOD));
-// Unused.
+// This is all LF, so doesn't matter.
+assign pwr_oe2 = 1'b0;
assign pwr_lo = 1'b0;
+
+assign dbg = negedge_cnt[3];
+
endmodule
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