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1 //-----------------------------------------------------------------------------
2 // ISO14443-A support for the Proxmark III
3 // Gerhard de Koning Gans, April 2008
4 //-----------------------------------------------------------------------------
5
6 // constants for the different modes:
7 `define SNIFFER 3'b000
8 `define TAGSIM_LISTEN 3'b001
9 `define TAGSIM_MOD 3'b010
10 `define READER_LISTEN 3'b011
11 `define READER_MOD 3'b100
12
13 module hi_iso14443a(
14 pck0, ck_1356meg, ck_1356megb,
15 pwr_lo, pwr_hi, pwr_oe1, pwr_oe2, pwr_oe3, pwr_oe4,
16 adc_d, adc_clk,
17 ssp_frame, ssp_din, ssp_dout, ssp_clk,
18 cross_hi, cross_lo,
19 dbg,
20 mod_type
21 );
22 input pck0, ck_1356meg, ck_1356megb;
23 output pwr_lo, pwr_hi, pwr_oe1, pwr_oe2, pwr_oe3, pwr_oe4;
24 input [7:0] adc_d;
25 output adc_clk;
26 input ssp_dout;
27 output ssp_frame, ssp_din, ssp_clk;
28 input cross_hi, cross_lo;
29 output dbg;
30 input [2:0] mod_type;
31
32
33 wire adc_clk = ck_1356meg;
34
35
36
37 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
38 // Reader -> PM3:
39 // detecting and shaping the reader's signal. Reader will modulate the carrier by 100% (signal is either on or off). Use a
40 // hysteresis (Schmitt Trigger) to avoid false triggers during slowly increasing or decreasing carrier amplitudes
41 reg after_hysteresis;
42 reg [11:0] has_been_low_for;
43
44 always @(negedge adc_clk)
45 begin
46 if(adc_d >= 16) after_hysteresis <= 1'b1; // U >= 1,14V -> after_hysteresis = 1
47 else if(adc_d < 8) after_hysteresis <= 1'b0; // U < 1,04V -> after_hysteresis = 0
48 // Note: was >= 3,53V and <= 1,19V. The new trigger values allow more reliable detection of the first bit
49 // (it might not reach 3,53V due to the high time constant of the high pass filter in the analogue RF part).
50 // In addition, the new values are more in line with ISO14443-2: "The PICC shall detect the ”End of Pause” after the field exceeds
51 // 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.
52
53
54 // detecting a loss of reader's field (adc_d < 192 for 4096 clock cycles). If this is the case,
55 // set the detected reader signal (after_hysteresis) to '1' (unmodulated)
56 if(adc_d >= 192)
57 begin
58 has_been_low_for <= 12'd0;
59 end
60 else
61 begin
62 if(has_been_low_for == 12'd4095)
63 begin
64 has_been_low_for <= 12'd0;
65 after_hysteresis <= 1'b1;
66 end
67 else
68 begin
69 has_been_low_for <= has_been_low_for + 1;
70 end
71 end
72
73 end
74
75
76
77 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
78 // Reader -> PM3
79 // detect when a reader is active (modulating). We assume that the reader is active, if we see the carrier off for at least 8
80 // carrier cycles. We assume that the reader is inactive, if the carrier stayed high for at least 256 carrier cycles.
81 reg deep_modulation;
82 reg [2:0] deep_counter;
83 reg [8:0] saw_deep_modulation;
84
85 always @(negedge adc_clk)
86 begin
87 if(~(| adc_d[7:0])) // if adc_d == 0 (U <= 0,94V)
88 begin
89 if(deep_counter == 3'd7) // adc_d == 0 for 8 adc_clk ticks -> deep_modulation (by reader)
90 begin
91 deep_modulation <= 1'b1;
92 saw_deep_modulation <= 8'd0;
93 end
94 else
95 deep_counter <= deep_counter + 1;
96 end
97 else
98 begin
99 deep_counter <= 3'd0;
100 if(saw_deep_modulation == 8'd255) // adc_d != 0 for 256 adc_clk ticks -> deep_modulation is over, probably waiting for tag's response
101 deep_modulation <= 1'b0;
102 else
103 saw_deep_modulation <= saw_deep_modulation + 1;
104 end
105 end
106
107
108
109 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
110 // Tag -> PM3
111 // filter the input for a tag's signal. The filter box needs the 4 previous input values and is a gaussian derivative filter
112 // for noise reduction and edge detection.
113 // store 4 previous samples:
114 reg [7:0] input_prev_4, input_prev_3, input_prev_2, input_prev_1;
115 // convert to signed signals (and multiply by two for samples at t-4 and t)
116 wire signed [10:0] input_prev_4_times_2 = {0, 0, input_prev_4, 0};
117 wire signed [10:0] input_prev_3_times_1 = {0, 0, 0, input_prev_3};
118 wire signed [10:0] input_prev_1_times_1 = {0, 0, 0, input_prev_1};
119 wire signed [10:0] adc_d_times_2 = {0, 0, adc_d, 0};
120
121 wire signed [10:0] tmp_1, tmp_2;
122 wire signed [10:0] adc_d_filtered;
123 integer i;
124
125 assign tmp_1 = input_prev_4_times_2 + input_prev_3_times_1;
126 assign tmp_2 = input_prev_1_times_1 + adc_d_times_2;
127
128 always @(negedge adc_clk)
129 begin
130 // for (i = 3; i > 0; i = i - 1)
131 // begin
132 // input_shift[i] <= input_shift[i-1];
133 // end
134 // input_shift[0] <= adc_d;
135 input_prev_4 <= input_prev_3;
136 input_prev_3 <= input_prev_2;
137 input_prev_2 <= input_prev_1;
138 input_prev_1 <= adc_d;
139 end
140
141 // assign adc_d_filtered = (input_shift[3] << 1) + input_shift[2] - input_shift[0] - (adc_d << 1);
142 assign adc_d_filtered = tmp_1 - tmp_2;
143
144
145 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
146 // internal FPGA timing. Maximum required period is 128 carrier clock cycles for a full 8 Bit transfer to ARM. (i.e. we need a
147 // 7 bit counter). Adjust its frequency to external reader's clock when simulating a tag or sniffing.
148 reg pre_after_hysteresis;
149 reg [3:0] reader_falling_edge_time;
150 reg [6:0] negedge_cnt;
151
152 always @(negedge adc_clk)
153 begin
154 // detect a reader signal's falling edge and remember its timing:
155 pre_after_hysteresis <= after_hysteresis;
156 if (pre_after_hysteresis && ~after_hysteresis)
157 begin
158 reader_falling_edge_time[3:0] <= negedge_cnt[3:0];
159 end
160
161 // adjust internal timer counter if necessary:
162 if (negedge_cnt[3:0] == 4'd13 && (mod_type == `SNIFFER || mod_type == `TAGSIM_LISTEN) && deep_modulation)
163 begin
164 if (reader_falling_edge_time == 4'd1) // reader signal changes right after sampling. Better sample earlier next time.
165 begin
166 negedge_cnt <= negedge_cnt + 2; // time warp
167 end
168 else if (reader_falling_edge_time == 4'd0) // reader signal changes right before sampling. Better sample later next time.
169 begin
170 negedge_cnt <= negedge_cnt; // freeze time
171 end
172 else
173 begin
174 negedge_cnt <= negedge_cnt + 1; // Continue as usual
175 end
176 reader_falling_edge_time[3:0] <= 4'd8; // adjust only once per detected edge
177 end
178 else if (negedge_cnt == 7'd127) // normal operation: count from 0 to 127
179 begin
180 negedge_cnt <= 0;
181 end
182 else
183 begin
184 negedge_cnt <= negedge_cnt + 1;
185 end
186 end
187
188
189 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
190 // Tag -> PM3:
191 // determine best possible time for starting/resetting the modulation detector.
192 reg [3:0] mod_detect_reset_time;
193
194 always @(negedge adc_clk)
195 begin
196 if (mod_type == `READER_LISTEN)
197 // (our) reader signal changes at t=1, tag response expected n*16+4 ticks later, further delayed by
198 // 3 ticks ADC conversion.
199 // 1 + 4 + 3 = 8
200 begin
201 mod_detect_reset_time <= 4'd8;
202 end
203 else
204 if (mod_type == `SNIFFER)
205 begin
206 // detect a rising edge of reader's signal and sync modulation detector to the tag's answer:
207 if (~pre_after_hysteresis && after_hysteresis && deep_modulation)
208 // reader signal rising edge detected at negedge_cnt[3:0]. This signal had been delayed
209 // 9 ticks by the RF part + 3 ticks by the A/D converter + 1 tick to assign to after_hysteresis.
210 // The tag will respond n*16 + 4 ticks later + 3 ticks A/D converter delay.
211 // - 9 - 3 - 1 + 4 + 3 = -6
212 begin
213 mod_detect_reset_time <= negedge_cnt[3:0] - 4'd4;
214 end
215 end
216 end
217
218
219 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
220 // Tag -> PM3:
221 // modulation detector. Looks for the steepest falling and rising edges within a 16 clock period. If there is both a significant
222 // falling and rising edge (in any order), a modulation is detected.
223 reg signed [10:0] rx_mod_falling_edge_max;
224 reg signed [10:0] rx_mod_rising_edge_max;
225 reg curbit;
226
227 always @(negedge adc_clk)
228 begin
229 if(negedge_cnt[3:0] == mod_detect_reset_time)
230 begin
231 // detect modulation signal: if modulating, there must have been a falling AND a rising edge
232 if (rx_mod_falling_edge_max > 5 && rx_mod_rising_edge_max > 5)
233 curbit <= 1'b1; // modulation
234 else
235 curbit <= 1'b0; // no modulation
236 // reset modulation detector
237 rx_mod_rising_edge_max <= 0;
238 rx_mod_falling_edge_max <= 0;
239 end
240 else // look for steepest edges (slopes)
241 begin
242 if (adc_d_filtered > 0)
243 begin
244 if (adc_d_filtered > rx_mod_falling_edge_max)
245 rx_mod_falling_edge_max <= adc_d_filtered;
246 end
247 else
248 begin
249 if (-adc_d_filtered > rx_mod_rising_edge_max)
250 rx_mod_rising_edge_max <= -adc_d_filtered;
251 end
252 end
253
254 end
255
256
257
258 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
259 // Tag+Reader -> PM3
260 // sample 4 bits reader data and 4 bits tag data for sniffing
261 reg [3:0] reader_data;
262 reg [3:0] tag_data;
263
264 always @(negedge adc_clk)
265 begin
266 if(negedge_cnt[3:0] == 4'd0)
267 begin
268 reader_data[3:0] <= {reader_data[2:0], after_hysteresis};
269 tag_data[3:0] <= {tag_data[2:0], curbit};
270 end
271 end
272
273
274
275 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
276 // PM3 -> Tag:
277 // a delay line to ensure that we send the (emulated) tag's answer at the correct time according to ISO14443-3
278 reg [31:0] mod_sig_buf;
279 reg [4:0] mod_sig_ptr;
280 reg mod_sig;
281
282 always @(negedge adc_clk)
283 begin
284 if(negedge_cnt[3:0] == 4'd0) // sample data at rising edge of ssp_clk - ssp_dout changes at the falling edge.
285 begin
286 mod_sig_buf[31:2] <= mod_sig_buf[30:1]; // shift
287 if (~ssp_dout && ~mod_sig_buf[1])
288 mod_sig_buf[1] <= 1'b0; // delete the correction bit (a single 1 preceded and succeeded by 0)
289 else
290 mod_sig_buf[1] <= mod_sig_buf[0];
291 mod_sig_buf[0] <= ssp_dout; // add new data to the delay line
292
293 mod_sig = mod_sig_buf[mod_sig_ptr]; // the delayed signal.
294 end
295 end
296
297
298
299 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
300 // PM3 -> Tag, internal timing:
301 // a timer for the 1172 cycles fdt (Frame Delay Time). Start the timer with a rising edge of the reader's signal.
302 // set fdt_elapsed when we no longer need to delay data. Set fdt_indicator when we can start sending data.
303 // Note: the FPGA only takes care for the 1172 delay. To achieve an additional 1236-1172=64 ticks delay, the ARM must send
304 // a correction bit (before the start bit). The correction bit will be coded as 00010000, i.e. it adds 4 bits to the
305 // transmission stream, causing the required additional delay.
306 reg [10:0] fdt_counter;
307 reg fdt_indicator, fdt_elapsed;
308 reg [3:0] mod_sig_flip;
309 reg [3:0] sub_carrier_cnt;
310
311 // we want to achieve a delay of 1172. The RF part already has delayed the reader signals's rising edge
312 // 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
313 // count to 1172 - 9 - 3 - 32 = 1128
314 `define FDT_COUNT 11'd1128
315
316 // The ARM must not send too early, otherwise the mod_sig_buf will overflow, therefore signal that we are ready
317 // 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.
318 // fdt_indicator could appear at ssp_din after 1 tick, the transfer needs 16 ticks, the ARM can send 128 ticks later.
319 // 1128 - 464 - 1 - 128 - 8 = 535
320 `define FDT_INDICATOR_COUNT 11'd535
321
322 // reset on a pause in listen mode. I.e. the counter starts when the pause is over:
323 assign fdt_reset = ~after_hysteresis && mod_type == `TAGSIM_LISTEN;
324
325 always @(negedge adc_clk)
326 begin
327 if (fdt_reset)
328 begin
329 fdt_counter <= 11'd0;
330 fdt_elapsed <= 1'b0;
331 fdt_indicator <= 1'b0;
332 end
333 else
334 begin
335 if(fdt_counter == `FDT_COUNT)
336 begin
337 if(~fdt_elapsed) // just reached fdt.
338 begin
339 mod_sig_flip <= negedge_cnt[3:0]; // start modulation at this time
340 sub_carrier_cnt <= 4'd0; // subcarrier phase in sync with start of modulation
341 fdt_elapsed <= 1'b1;
342 end
343 else
344 begin
345 sub_carrier_cnt <= sub_carrier_cnt + 1;
346 end
347 end
348 else
349 begin
350 fdt_counter <= fdt_counter + 1;
351 end
352 end
353
354 if(fdt_counter == `FDT_INDICATOR_COUNT) fdt_indicator <= 1'b1;
355 end
356
357
358 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
359 // PM3 -> Reader or Tag
360 // assign a modulation signal to the antenna. This signal is either a delayed signal (to achieve fdt when sending to a reader)
361 // or undelayed when sending to a tag
362 reg mod_sig_coil;
363
364 always @(negedge adc_clk)
365 begin
366 if (mod_type == `TAGSIM_MOD) // need to take care of proper fdt timing
367 begin
368 if(fdt_counter == `FDT_COUNT)
369 begin
370 if(fdt_elapsed)
371 begin
372 if(negedge_cnt[3:0] == mod_sig_flip) mod_sig_coil <= mod_sig;
373 end
374 else
375 begin
376 mod_sig_coil <= mod_sig; // just reached fdt. Immediately assign signal to coil
377 end
378 end
379 end
380 else // other modes: don't delay
381 begin
382 mod_sig_coil <= ssp_dout;
383 end
384 end
385
386
387
388 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
389 // PM3 -> Reader
390 // determine the required delay in the mod_sig_buf (set mod_sig_ptr).
391 reg temp_buffer_reset;
392
393 always @(negedge adc_clk)
394 begin
395 if(fdt_reset)
396 begin
397 mod_sig_ptr <= 5'd0;
398 temp_buffer_reset = 1'b0;
399 end
400 else
401 begin
402 if(fdt_counter == `FDT_COUNT && ~fdt_elapsed) // if we just reached fdt
403 if(~(| mod_sig_ptr[4:0]))
404 mod_sig_ptr <= 5'd8; // ... but didn't buffer a 1 yet, delay next 1 by n*128 ticks.
405 else
406 temp_buffer_reset = 1'b1; // else no need for further delays.
407
408 if(negedge_cnt[3:0] == 4'd0) // at rising edge of ssp_clk - ssp_dout changes at the falling edge.
409 begin
410 if((ssp_dout || (| mod_sig_ptr[4:0])) && ~fdt_elapsed) // buffer a 1 (and all subsequent data) until fdt is reached.
411 if (mod_sig_ptr == 5'd31)
412 mod_sig_ptr <= 5'd0; // buffer overflow - data loss.
413 else
414 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.
415 else if(fdt_elapsed && ~temp_buffer_reset)
416 begin
417 // wait for the next 1 after fdt_elapsed before fixing the delay and starting modulation. This ensures that the response can only happen
418 // at intervals of 8 * 16 = 128 adc_clk ticks (as defined in ISO14443-3)
419 if(ssp_dout)
420 temp_buffer_reset = 1'b1;
421 if(mod_sig_ptr == 5'd1)
422 mod_sig_ptr <= 5'd8; // still nothing received, need to go for the next interval
423 else
424 mod_sig_ptr <= mod_sig_ptr - 1; // decrease buffer.
425 end
426 end
427 end
428 end
429
430
431
432 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
433 // FPGA -> ARM communication:
434 // buffer 8 bits data to be sent to ARM. Shift them out bit by bit.
435 reg [7:0] to_arm;
436
437 always @(negedge adc_clk)
438 begin
439 if (negedge_cnt[5:0] == 6'd63) // fill the buffer
440 begin
441 if (mod_type == `SNIFFER)
442 begin
443 if(deep_modulation) // a reader is sending (or there's no field at all)
444 begin
445 to_arm <= {reader_data[3:0], 4'b0000}; // don't send tag data
446 end
447 else
448 begin
449 to_arm <= {reader_data[3:0], tag_data[3:0]};
450 end
451 end
452 else
453 begin
454 to_arm[7:0] <= {mod_sig_ptr[4:0], mod_sig_flip[3:1]}; // feedback timing information
455 end
456 end
457
458 if(negedge_cnt[2:0] == 3'b000 && mod_type == `SNIFFER) // shift at double speed
459 begin
460 // Don't shift if we just loaded new data, obviously.
461 if(negedge_cnt[5:0] != 6'd0)
462 begin
463 to_arm[7:1] <= to_arm[6:0];
464 end
465 end
466
467 if(negedge_cnt[3:0] == 4'b0000 && mod_type != `SNIFFER)
468 begin
469 // Don't shift if we just loaded new data, obviously.
470 if(negedge_cnt[6:0] != 7'd0)
471 begin
472 to_arm[7:1] <= to_arm[6:0];
473 end
474 end
475
476 end
477
478
479 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
480 // FPGA -> ARM communication:
481 // generate a ssp clock and ssp frame signal for the synchronous transfer from/to the ARM
482 reg ssp_clk;
483 reg ssp_frame;
484 reg [2:0] ssp_frame_counter;
485
486 always @(negedge adc_clk)
487 begin
488 if(mod_type == `SNIFFER)
489 // SNIFFER mode (ssp_clk = adc_clk / 8, ssp_frame clock = adc_clk / 64)):
490 begin
491 if(negedge_cnt[2:0] == 3'd0)
492 ssp_clk <= 1'b1;
493 if(negedge_cnt[2:0] == 3'd4)
494 ssp_clk <= 1'b0;
495
496 if(negedge_cnt[5:0] == 6'd0) // ssp_frame rising edge indicates start of frame
497 ssp_frame <= 1'b1;
498 if(negedge_cnt[5:0] == 6'd8)
499 ssp_frame <= 1'b0;
500 end
501 else
502 // all other modes (ssp_clk = adc_clk / 16, ssp_frame clock = adc_clk / 128):
503 begin
504 if(negedge_cnt[3:0] == 4'd0)
505 ssp_clk <= 1'b1;
506 if(negedge_cnt[3:0] == 4'd8)
507 ssp_clk <= 1'b0;
508
509 if(negedge_cnt[6:0] == 7'd7) // ssp_frame rising edge indicates start of frame
510 ssp_frame <= 1'b1;
511 if(negedge_cnt[6:0] == 7'd23)
512 ssp_frame <= 1'b0;
513 end
514 end
515
516
517
518 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
519 // FPGA -> ARM communication:
520 // select the data to be sent to ARM
521 reg bit_to_arm;
522 reg sendbit;
523
524 always @(negedge adc_clk)
525 begin
526 if(negedge_cnt[3:0] == 4'd0)
527 begin
528 // What do we communicate to the ARM
529 if(mod_type == `TAGSIM_LISTEN)
530 sendbit = after_hysteresis;
531 else if(mod_type == `TAGSIM_MOD)
532 /* if(fdt_counter > 11'd772) sendbit = mod_sig_coil; // huh?
533 else */
534 sendbit = fdt_indicator;
535 else if (mod_type == `READER_LISTEN)
536 sendbit = curbit;
537 else
538 sendbit = 1'b0;
539 end
540
541
542 if(mod_type == `SNIFFER)
543 // send sampled reader and tag data:
544 bit_to_arm = to_arm[7];
545 else if (mod_type == `TAGSIM_MOD && fdt_elapsed && temp_buffer_reset)
546 // send timing information:
547 bit_to_arm = to_arm[7];
548 else
549 // send data or fdt_indicator
550 bit_to_arm = sendbit;
551 end
552
553
554
555
556 assign ssp_din = bit_to_arm;
557
558 // Subcarrier (adc_clk/16, for TAGSIM_MOD only).
559 wire sub_carrier;
560 assign sub_carrier = ~sub_carrier_cnt[3];
561
562 // in READER_MOD: drop carrier for mod_sig_coil==1 (pause); in READER_LISTEN: carrier always on; in other modes: carrier always off
563 assign pwr_hi = (ck_1356megb & (((mod_type == `READER_MOD) & ~mod_sig_coil) || (mod_type == `READER_LISTEN)));
564
565
566 // Enable HF antenna drivers:
567 assign pwr_oe1 = 1'b0;
568 assign pwr_oe3 = 1'b0;
569
570 // TAGSIM_MOD: short circuit antenna with different resistances (modulated by sub_carrier modulated by mod_sig_coil)
571 // for pwr_oe4 = 1 (tristate): antenna load = 10k || 33 = 32,9 Ohms
572 // for pwr_oe4 = 0 (active): antenna load = 10k || 33 || 33 = 16,5 Ohms
573 assign pwr_oe4 = ~(mod_sig_coil & sub_carrier & (mod_type == `TAGSIM_MOD));
574
575 // This is all LF, so doesn't matter.
576 assign pwr_oe2 = 1'b0;
577 assign pwr_lo = 1'b0;
578
579
580 assign dbg = negedge_cnt[3];
581
582 endmodule
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