output dbg;
input [2:0] mod_type;
-reg ssp_clk;
-reg ssp_frame;
-wire adc_clk;
-assign adc_clk = ck_1356meg;
+wire adc_clk = ck_1356meg;
+
-reg after_hysteresis, after_hysteresis_prev1, after_hysteresis_prev2, after_hysteresis_prev3, after_hysteresis_prev4;
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// Reader -> PM3:
+// detecting and shaping the reader's signal. Reader will modulate the carrier by 100% (signal is either on or off). Use a
+// hysteresis (Schmitt Trigger) to avoid false triggers during slowly increasing or decreasing carrier amplitudes
+reg after_hysteresis;
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; // 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 >= 16) after_hysteresis <= 1'b1; // U >= 1,14V -> after_hysteresis = 1
+ else if(adc_d < 8) after_hysteresis <= 1'b0; // U < 1,04V -> after_hysteresis = 0
+ // Note: was >= 3,53V and <= 1,19V. The new trigger values allow more reliable detection of the first bit
+ // (it might not reach 3,53V due to the high time constant of the high pass filter in the analogue RF part).
+ // In addition, the new values are more in line with ISO14443-2: "The PICC shall detect the ”End of Pause” after the field exceeds
+ // 5% of H_INITIAL and before it exceeds 60% of H_INITIAL." Depending on the signal strength, 60% might well be less than 3,53V.
+
+ // detecting a loss of reader's field (adc_d < 192 for 4096 clock cycles). If this is the case,
+ // set the detected reader signal (after_hysteresis) to '1' (unmodulated)
+ if(adc_d >= 192)
+ begin
+ 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;
+ end
+ else
+ begin
+ has_been_low_for <= has_been_low_for + 1;
+ end
+ end
+
+end
+
+
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// Reader -> PM3
+// detect when a reader is active (modulating). We assume that the reader is active, if we see the carrier off for at least 8
+// carrier cycles. We assume that the reader is inactive, if the carrier stayed high for at least 256 carrier cycles.
+reg deep_modulation;
+reg [2:0] deep_counter;
+reg [8:0] saw_deep_modulation;
+
+always @(negedge adc_clk)
+begin
if(~(| adc_d[7:0])) // if adc_d == 0 (U <= 0,94V)
begin
- if(deep_counter == 3'd7) // adc_d == 0 for 7 adc_clk ticks -> deep_modulation (by reader)
+ if(deep_counter == 3'd7) // adc_d == 0 for 8 adc_clk ticks -> deep_modulation (by reader)
begin
deep_modulation <= 1'b1;
saw_deep_modulation <= 8'd0;
else
begin
deep_counter <= 3'd0;
- if(saw_deep_modulation == 8'd255) // adc_d != 0 for 255 adc_clk ticks -> deep_modulation is over, now waiting for tag's response
+ if(saw_deep_modulation == 8'd255) // adc_d != 0 for 256 adc_clk ticks -> deep_modulation is over, probably waiting for tag's response
deep_modulation <= 1'b0;
else
saw_deep_modulation <= saw_deep_modulation + 1;
end
-
- if(after_hysteresis)
- begin
- 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; // 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
-// 128 periods of carrier frequency => 7-bit counter [negedge_cnt]
-reg [6:0] negedge_cnt;
-reg bit1, bit2, bit3, bit4;
-reg curbit;
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// Tag -> PM3
+// filter the input for a tag's signal. The filter box needs the 4 previous input values and is a gaussian derivative filter
+// for noise reduction and edge detection.
+// store 4 previous samples:
+reg [7:0] input_prev_4, input_prev_3, input_prev_2, input_prev_1;
-// 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;
+always @(negedge adc_clk)
+begin
+ input_prev_4 <= input_prev_3;
+ input_prev_3 <= input_prev_2;
+ input_prev_2 <= input_prev_1;
+ input_prev_1 <= adc_d;
+end
-// 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);
+// adc_d_filtered = 2*input_prev4 + 1*input_prev3 + 0*input_prev2 - 1*input_prev1 - 2*input
+// = (2*input_prev4 + input_prev3) - (2*input + input_prev1)
+wire [8:0] input_prev_4_times_2 = input_prev_4 << 1;
+wire [8:0] adc_d_times_2 = 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;
+wire [9:0] tmp1 = input_prev_4_times_2 + input_prev_3;
+wire [9:0] tmp2 = adc_d_times_2 + input_prev_1;
-// A register to send 8 Bit results to the arm
-reg [7:0] to_arm;
+// convert intermediate signals to signed and calculate the filter output
+wire signed [10:0] adc_d_filtered = {1'b0, tmp1} - {1'b0, tmp2};
-reg bit_to_arm;
-reg fdt_indicator, fdt_elapsed;
-reg [10:0] fdt_counter;
-//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;
-reg [3:0] sub_carrier_cnt;
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// internal FPGA timing. Maximum required period is 128 carrier clock cycles for a full 8 Bit transfer to ARM. (i.e. we need a
+// 7 bit counter). Adjust its frequency to external reader's clock when simulating a tag or sniffing.
+reg pre_after_hysteresis;
+reg [3:0] reader_falling_edge_time;
+reg [6:0] negedge_cnt;
-// ADC data appears on the rising edge, so sample it on the falling edge
always @(negedge adc_clk)
begin
- // ------------------------------------------------------------------------------------------------------------------------------------------------------------------
- // 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 ((mod_type == `TAGSIM_MOD) || (mod_type == `TAGSIM_LISTEN))
+ // detect a reader signal's falling edge and remember its timing:
+ pre_after_hysteresis <= after_hysteresis;
+ if (pre_after_hysteresis && ~after_hysteresis)
begin
- 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.
+ reader_falling_edge_time[3:0] <= negedge_cnt[3:0];
+ end
+
+ // adjust internal timer counter if necessary:
+ if (negedge_cnt[3:0] == 4'd13 && (mod_type == `SNIFFER || mod_type == `TAGSIM_LISTEN) && deep_modulation)
+ begin
+ if (reader_falling_edge_time == 4'd1) // reader signal changes right after sampling. Better sample earlier next time.
begin
- 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
+ negedge_cnt <= negedge_cnt + 2; // time warp
+ end
+ else if (reader_falling_edge_time == 4'd0) // reader signal changes right before sampling. Better sample later next time.
+ begin
+ negedge_cnt <= negedge_cnt; // freeze time
end
else
begin
- fdt_counter <= fdt_counter + 1; // Count until 1155
+ negedge_cnt <= negedge_cnt + 1; // Continue as usual
end
+ reader_falling_edge_time[3:0] <= 4'd8; // adjust only once per detected edge
end
- else // other modes: don't use the delay line.
+ else if (negedge_cnt == 7'd127) // normal operation: count from 0 to 127
begin
- mod_sig_coil <= ssp_dout;
+ negedge_cnt <= 0;
end
-
-
- //-------------------------------------------------------------------------------------------------------------------------------------------
- // Relevant for READER_LISTEN only
- // look for steepest falling and rising edges:
+ else
+ begin
+ negedge_cnt <= negedge_cnt + 1;
+ end
+end
- if(negedge_cnt[3:0] == 4'd1) // reset modulation detector. Save current edge.
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// Tag -> PM3:
+// determine best possible time for starting/resetting the modulation detector.
+reg [3:0] mod_detect_reset_time;
+
+always @(negedge adc_clk)
+begin
+ if (mod_type == `READER_LISTEN)
+ // (our) reader signal changes at negedge_cnt[3:0]=9, tag response expected to start n*16+4 ticks later, further delayed by
+ // 3 ticks ADC conversion. The maximum filter output (edge detected) will be detected after subcarrier zero crossing (+7 ticks).
+ // To allow some timing variances, we want to have the maximum filter outputs well within the detection window, i.e.
+ // at mod_detect_reset_time+4 and mod_detect_reset_time+12 (-4 ticks).
+ // 9 + 4 + 3 + 7 - 4 = 19. 19 mod 16 = 3
begin
- if (adc_d_filtered > 0)
- begin
- rx_mod_falling_edge_max <= adc_d_filtered;
- rx_mod_rising_edge_max <= 0;
- end
- else
+ mod_detect_reset_time <= 4'd4;
+ end
+ else
+ if (mod_type == `SNIFFER)
+ begin
+ // detect a rising edge of reader's signal and sync modulation detector to the tag's answer:
+ if (~pre_after_hysteresis && after_hysteresis && deep_modulation)
+ // reader signal rising edge detected at negedge_cnt[3:0]. This signal had been delayed
+ // 9 ticks by the RF part + 3 ticks by the A/D converter + 1 tick to assign to after_hysteresis.
+ // Then the same as above.
+ // - 9 - 3 - 1 + 4 + 3 + 7 - 4 = -3
begin
- rx_mod_falling_edge_max <= 0;
- rx_mod_rising_edge_max <= -adc_d_filtered;
+ mod_detect_reset_time <= negedge_cnt[3:0] - 4'd3;
end
end
- else // detect modulation
+end
+
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// Tag -> PM3:
+// modulation detector. Looks for the steepest falling and rising edges within a 16 clock period. If there is both a significant
+// falling and rising edge (in any order), a modulation is detected.
+reg signed [10:0] rx_mod_falling_edge_max;
+reg signed [10:0] rx_mod_rising_edge_max;
+reg curbit;
+
+`define EDGE_DETECT_THRESHOLD 5
+
+always @(negedge adc_clk)
+begin
+ if(negedge_cnt[3:0] == mod_detect_reset_time)
+ begin
+ // detect modulation signal: if modulating, there must have been a falling AND a rising edge
+ if ((rx_mod_falling_edge_max > `EDGE_DETECT_THRESHOLD) && (rx_mod_rising_edge_max < -`EDGE_DETECT_THRESHOLD))
+ curbit <= 1'b1; // modulation
+ else
+ curbit <= 1'b0; // no modulation
+ // reset modulation detector
+ rx_mod_rising_edge_max <= 0;
+ rx_mod_falling_edge_max <= 0;
+ end
+ else // look for steepest edges (slopes)
begin
if (adc_d_filtered > 0)
begin
end
else
begin
- if (-adc_d_filtered > rx_mod_rising_edge_max)
- rx_mod_rising_edge_max <= -adc_d_filtered;
+ if (adc_d_filtered < rx_mod_rising_edge_max)
+ rx_mod_rising_edge_max <= adc_d_filtered;
end
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;
+end
+
- // 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)
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// Tag+Reader -> PM3
+// sample 4 bits reader data and 4 bits tag data for sniffing
+reg [3:0] reader_data;
+reg [3:0] tag_data;
+
+always @(negedge adc_clk)
+begin
+ if(negedge_cnt[3:0] == 4'd0)
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
+ reader_data[3:0] <= {reader_data[2:0], after_hysteresis};
+ tag_data[3:0] <= {tag_data[2:0], curbit};
+ end
+end
- if(negedge_cnt[3:0] == 4'd1)
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// PM3 -> Reader:
+// a delay line to ensure that we send the (emulated) tag's answer at the correct time according to ISO14443-3
+reg [31:0] mod_sig_buf;
+reg [4:0] mod_sig_ptr;
+reg mod_sig;
+
+always @(negedge adc_clk)
+begin
+ if(negedge_cnt[3:0] == 4'd0) // sample data at rising edge of ssp_clk - ssp_dout changes at the falling edge.
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;
+ mod_sig_buf[31:2] <= mod_sig_buf[30:1]; // shift
+ if (~ssp_dout && ~mod_sig_buf[1])
+ mod_sig_buf[1] <= 1'b0; // delete the correction bit (a single 1 preceded and succeeded by 0)
else
- sendbit = 1'b0;
+ mod_sig_buf[1] <= mod_sig_buf[0];
+ mod_sig_buf[0] <= ssp_dout; // add new data to the delay line
+
+ mod_sig = mod_sig_buf[mod_sig_ptr]; // the delayed signal.
end
+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)
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// PM3 -> Reader, internal timing:
+// a timer for the 1172 cycles fdt (Frame Delay Time). Start the timer with a rising edge of the reader's signal.
+// set fdt_elapsed when we no longer need to delay data. Set fdt_indicator when we can start sending data.
+// Note: the FPGA only takes care for the 1172 delay. To achieve an additional 1236-1172=64 ticks delay, the ARM must send
+// a 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 additional delay.
+reg [10:0] fdt_counter;
+reg fdt_indicator, fdt_elapsed;
+reg [3:0] mod_sig_flip;
+reg [3:0] sub_carrier_cnt;
+
+// we want to achieve a delay of 1172. The RF part already has delayed the reader signals's rising edge
+// by 9 ticks, the ADC took 3 ticks and there is always a delay of 32 ticks by the mod_sig_buf. Therefore need to
+// count to 1172 - 9 - 3 - 32 = 1128
+`define FDT_COUNT 11'd1128
+
+// The ARM must not send too early, otherwise the mod_sig_buf will overflow, therefore signal that we are ready
+// with fdt_indicator. The mod_sig_buf can buffer 29 excess data bits, i.e. a maximum delay of 29 * 16 = 464 adc_clk ticks.
+// fdt_indicator is assigned to sendbit after at least 1 tick, the transfer to ARM needs minimum 8 ticks. Response from
+// ARM could appear at ssp_dout 8 ticks later.
+// 1128 - 464 - 1 - 8 - 8 = 647
+`define FDT_INDICATOR_COUNT 11'd647
+// Note: worst case, assignment to sendbit takes 15 ticks more, and transfer to ARM needs 7*16 = 112 ticks more.
+// When the ARM's response then appears, the fdt_count is already 647 + 15 + 112 = 774, which still allows the ARM a possible
+// response window of 1128 - 774 = 354 ticks.
+
+// reset on a pause in listen mode. I.e. the counter starts when the pause is over:
+assign fdt_reset = ~after_hysteresis && mod_type == `TAGSIM_LISTEN;
+
+always @(negedge adc_clk)
+begin
+ if (fdt_reset)
begin
- if (negedge_cnt == 7'd63)
- begin
- if(deep_modulation) // a reader is sending (or there's no field at all)
+ fdt_counter <= 11'd0;
+ fdt_elapsed <= 1'b0;
+ fdt_indicator <= 1'b0;
+ end
+ else
+ begin
+ if(fdt_counter == `FDT_COUNT)
+ begin
+ if(~fdt_elapsed) // just reached fdt.
begin
- to_arm <= {after_hysteresis_prev1,after_hysteresis_prev2,after_hysteresis_prev3,after_hysteresis_prev4,1'b0,1'b0,1'b0,1'b0};
+ mod_sig_flip <= negedge_cnt[3:0]; // start modulation at this time
+ sub_carrier_cnt <= 4'd0; // subcarrier phase in sync with start of modulation
+ fdt_elapsed <= 1'b1;
end
else
begin
- to_arm <= {after_hysteresis_prev1,after_hysteresis_prev2,after_hysteresis_prev3,after_hysteresis_prev4,bit1,bit2,bit3,bit4};
- end
- negedge_cnt <= 0;
- end
+ sub_carrier_cnt <= sub_carrier_cnt + 1;
+ end
+ end
else
begin
- negedge_cnt <= negedge_cnt + 1;
+ fdt_counter <= fdt_counter + 1;
end
end
- else
- // other modes: 8 Bits info on queue delay
+
+ if(fdt_counter == `FDT_INDICATOR_COUNT) fdt_indicator <= 1'b1;
+end
+
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// PM3 -> Reader or Tag
+// assign a modulation signal to the antenna. This signal is either a delayed signal (to achieve fdt when sending to a reader)
+// or undelayed when sending to a tag
+reg mod_sig_coil;
+
+always @(negedge adc_clk)
+begin
+ if (mod_type == `TAGSIM_MOD) // need to take care of proper fdt timing
begin
- if(negedge_cnt == 7'd127)
+ if(fdt_counter == `FDT_COUNT)
begin
- if (mod_type == `TAGSIM_MOD)
+ if(fdt_elapsed)
begin
- to_arm[7:0] <= {mod_sig_ptr[4:0], mod_sig_flip[3:1]};
+ if(negedge_cnt[3:0] == mod_sig_flip) mod_sig_coil <= mod_sig;
end
else
begin
- to_arm[7:0] <= 8'd0;
+ mod_sig_coil <= mod_sig; // just reached fdt. Immediately assign signal to coil
end
- negedge_cnt <= 0;
end
- else
- begin
- negedge_cnt <= negedge_cnt + 1;
- end
- end
-
- if(negedge_cnt == 7'd1)
- begin
- after_hysteresis_prev1 <= after_hysteresis;
- bit1 <= curbit;
end
- if(negedge_cnt == 7'd17)
+ else // other modes: don't delay
begin
- after_hysteresis_prev2 <= after_hysteresis;
- bit2 <= curbit;
- end
- if(negedge_cnt == 7'd33)
+ mod_sig_coil <= ssp_dout;
+ end
+end
+
+
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// PM3 -> Reader
+// determine the required delay in the mod_sig_buf (set mod_sig_ptr).
+reg temp_buffer_reset;
+
+always @(negedge adc_clk)
+begin
+ if(fdt_reset)
begin
- after_hysteresis_prev3 <= after_hysteresis;
- bit3 <= curbit;
- end
- if(negedge_cnt == 7'd47)
+ mod_sig_ptr <= 5'd0;
+ temp_buffer_reset = 1'b0;
+ end
+ else
begin
- after_hysteresis_prev4 <= after_hysteresis;
- bit4 <= curbit;
+ if(fdt_counter == `FDT_COUNT && ~fdt_elapsed) // if we just reached fdt
+ if(~(| mod_sig_ptr[4:0]))
+ mod_sig_ptr <= 5'd8; // ... but didn't buffer a 1 yet, delay next 1 by n*128 ticks.
+ else
+ temp_buffer_reset = 1'b1; // else no need for further delays.
+
+ if(negedge_cnt[3:0] == 4'd0) // at rising edge of ssp_clk - ssp_dout changes at the falling edge.
+ begin
+ if((ssp_dout || (| mod_sig_ptr[4:0])) && ~fdt_elapsed) // buffer a 1 (and all subsequent data) until fdt is reached.
+ if (mod_sig_ptr == 5'd31)
+ mod_sig_ptr <= 5'd0; // buffer overflow - data loss.
+ else
+ mod_sig_ptr <= mod_sig_ptr + 1; // increase buffer (= increase delay by 16 adc_clk ticks). mod_sig_ptr always points ahead of first 1.
+ else if(fdt_elapsed && ~temp_buffer_reset)
+ begin
+ // 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 (as defined in ISO14443-3)
+ if(ssp_dout)
+ temp_buffer_reset = 1'b1;
+ if(mod_sig_ptr == 5'd1)
+ mod_sig_ptr <= 5'd8; // still nothing received, need to go for the next interval
+ else
+ mod_sig_ptr <= mod_sig_ptr - 1; // decrease buffer.
+ end
+ end
end
-
- //--------------------------------------------------------------------------------------------------------------------------------------------------------------
- // 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.
+end
+
+
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// FPGA -> ARM communication:
+// buffer 8 bits data to be sent to ARM. Shift them out bit by bit.
+reg [7:0] to_arm;
+
+always @(negedge adc_clk)
+begin
+ if (negedge_cnt[5:0] == 6'd63) // fill the buffer
begin
- 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.
+ if (mod_type == `SNIFFER)
begin
- // 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.
+ if(deep_modulation) // a reader is sending (or there's no field at all)
+ begin
+ to_arm <= {reader_data[3:0], 4'b0000}; // don't send tag data
+ end
+ else
+ begin
+ to_arm <= {reader_data[3:0], tag_data[3:0]};
+ end
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];
+ to_arm[7:0] <= {mod_sig_ptr[4:0], mod_sig_flip[3:1]}; // feedback timing information
+ end
+ end
+
+ if(negedge_cnt[2:0] == 3'b000 && mod_type == `SNIFFER) // shift at double speed
+ begin
+ // Don't shift if we just loaded new data, obviously.
+ if(negedge_cnt[5:0] != 6'd0)
+ begin
+ to_arm[7:1] <= to_arm[6:0];
+ end
+ end
+
+ if(negedge_cnt[3:0] == 4'b0000 && mod_type != `SNIFFER)
+ begin
+ // 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
- //-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
- // Communication to ARM (SSP Clock and data)
- // SNIFFER mode (ssp_clk = adc_clk / 8, ssp_frame clock = adc_clk / 64)):
+end
+
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// FPGA <-> ARM communication:
+// generate a ssp clock and ssp frame signal for the synchronous transfer from/to the ARM
+reg ssp_clk;
+reg ssp_frame;
+
+always @(negedge adc_clk)
+begin
if(mod_type == `SNIFFER)
+ // SNIFFER mode (ssp_clk = adc_clk / 8, ssp_frame clock = adc_clk / 64)):
begin
- if(negedge_cnt[2:0] == 3'b100)
- ssp_clk <= 1'b0;
-
- if(negedge_cnt[2:0] == 3'b000)
- begin
+ if(negedge_cnt[2:0] == 3'd0)
ssp_clk <= 1'b1;
- // Don't shift if we just loaded new data, obviously.
- if(negedge_cnt[5:0] != 6'd0)
- begin
- to_arm[7:1] <= to_arm[6:0];
- end
- end
+ if(negedge_cnt[2:0] == 3'd4)
+ ssp_clk <= 1'b0;
- if(negedge_cnt[5:4] == 2'b00)
- ssp_frame = 1'b1;
- else
- ssp_frame = 1'b0;
-
- bit_to_arm = to_arm[7];
+ if(negedge_cnt[5:0] == 6'd0) // ssp_frame rising edge indicates start of frame
+ ssp_frame <= 1'b1;
+ if(negedge_cnt[5:0] == 6'd8)
+ ssp_frame <= 1'b0;
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'd0)
+ ssp_clk <= 1'b1;
+ if(negedge_cnt[3:0] == 4'd8)
+ 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 (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[6:0] == 7'd7) // ssp_frame rising edge indicates start of frame
+ ssp_frame <= 1'b1;
+ if(negedge_cnt[6:0] == 7'd23)
+ ssp_frame <= 1'b0;
+ end
+end
- 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
-
- if (mod_type == `TAGSIM_MOD && fdt_elapsed && temp_buffer_reset)
- // transmit timing information
- bit_to_arm = to_arm[7];
+
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// FPGA -> ARM communication:
+// select the data to be sent to ARM
+reg bit_to_arm;
+reg sendbit;
+
+always @(negedge adc_clk)
+begin
+ if(negedge_cnt[3:0] == 4'd0)
+ 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
- // transmit data or fdt_indicator
- bit_to_arm = sendbit;
- end
-
-end //always @(negedge adc_clk)
+ sendbit = 1'b0;
+ end
-assign ssp_din = bit_to_arm;
+ if(mod_type == `SNIFFER)
+ // send sampled reader and tag data:
+ bit_to_arm = to_arm[7];
+ else if (mod_type == `TAGSIM_MOD && fdt_elapsed && temp_buffer_reset)
+ // send timing information:
+ bit_to_arm = to_arm[7];
+ else
+ // send data or fdt_indicator
+ bit_to_arm = sendbit;
+end
+
+
+
+
+assign ssp_din = bit_to_arm;
// Subcarrier (adc_clk/16, for TAGSIM_MOD only).
wire sub_carrier;
// 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));
+assign pwr_oe4 = mod_sig_coil & sub_carrier & (mod_type == `TAGSIM_MOD);
// This is all LF, so doesn't matter.
assign pwr_oe2 = 1'b0;
projects / proxmark3-svn / blobdiff