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1 //-----------------------------------------------------------------------------
2 // Miscellaneous routines for low frequency tag operations.
3 // Tags supported here so far are Texas Instruments (TI), HID
4 // Also routines for raw mode reading/simulating of LF waveform
5 //
6 //-----------------------------------------------------------------------------
7 #include <proxmark3.h>
8 #include "apps.h"
9 #include "hitag2.h"
10 #include "crc16.h"
11
12 void AcquireRawAdcSamples125k(BOOL at134khz)
13 {
14 if (at134khz)
15 FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz
16 else
17 FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz
18
19 FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_READER);
20
21 // Connect the A/D to the peak-detected low-frequency path.
22 SetAdcMuxFor(GPIO_MUXSEL_LOPKD);
23
24 // Give it a bit of time for the resonant antenna to settle.
25 SpinDelay(50);
26
27 // Now set up the SSC to get the ADC samples that are now streaming at us.
28 FpgaSetupSsc();
29
30 // Now call the acquisition routine
31 DoAcquisition125k();
32 }
33
34 // split into two routines so we can avoid timing issues after sending commands //
35 void DoAcquisition125k(void)
36 {
37 BYTE *dest = (BYTE *)BigBuf;
38 int n = sizeof(BigBuf);
39 int i;
40
41 memset(dest, 0, n);
42 i = 0;
43 for(;;) {
44 if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXRDY) {
45 AT91C_BASE_SSC->SSC_THR = 0x43;
46 LED_D_ON();
47 }
48 if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY) {
49 dest[i] = (BYTE)AT91C_BASE_SSC->SSC_RHR;
50 i++;
51 LED_D_OFF();
52 if (i >= n) break;
53 }
54 }
55 Dbprintf("buffer samples: %02x %02x %02x %02x %02x %02x %02x %02x ...",
56 dest[0], dest[1], dest[2], dest[3], dest[4], dest[5], dest[6], dest[7]);
57 }
58
59 void ModThenAcquireRawAdcSamples125k(int delay_off, int period_0, int period_1, BYTE *command)
60 {
61 BOOL at134khz;
62
63 /* Make sure the tag is reset */
64 FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
65 SpinDelay(2500);
66
67 // see if 'h' was specified
68 if (command[strlen((char *) command) - 1] == 'h')
69 at134khz = TRUE;
70 else
71 at134khz = FALSE;
72
73 if (at134khz)
74 FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz
75 else
76 FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz
77
78 FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_READER);
79
80 // Give it a bit of time for the resonant antenna to settle.
81 SpinDelay(50);
82 // And a little more time for the tag to fully power up
83 SpinDelay(2000);
84
85 // Now set up the SSC to get the ADC samples that are now streaming at us.
86 FpgaSetupSsc();
87
88 // now modulate the reader field
89 while(*command != '\0' && *command != ' ') {
90 FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
91 LED_D_OFF();
92 SpinDelayUs(delay_off);
93 if (at134khz)
94 FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz
95 else
96 FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz
97
98 FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_READER);
99 LED_D_ON();
100 if(*(command++) == '0')
101 SpinDelayUs(period_0);
102 else
103 SpinDelayUs(period_1);
104 }
105 FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
106 LED_D_OFF();
107 SpinDelayUs(delay_off);
108 if (at134khz)
109 FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz
110 else
111 FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz
112
113 FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_READER);
114
115 // now do the read
116 DoAcquisition125k();
117 }
118
119 /* blank r/w tag data stream
120 ...0000000000000000 01111111
121 1010101010101010101010101010101010101010101010101010101010101010
122 0011010010100001
123 01111111
124 101010101010101[0]000...
125
126 [5555fe852c5555555555555555fe0000]
127 */
128 void ReadTItag(void)
129 {
130 // some hardcoded initial params
131 // when we read a TI tag we sample the zerocross line at 2Mhz
132 // TI tags modulate a 1 as 16 cycles of 123.2Khz
133 // TI tags modulate a 0 as 16 cycles of 134.2Khz
134 #define FSAMPLE 2000000
135 #define FREQLO 123200
136 #define FREQHI 134200
137
138 signed char *dest = (signed char *)BigBuf;
139 int n = sizeof(BigBuf);
140 // int *dest = GraphBuffer;
141 // int n = GraphTraceLen;
142
143 // 128 bit shift register [shift3:shift2:shift1:shift0]
144 DWORD shift3 = 0, shift2 = 0, shift1 = 0, shift0 = 0;
145
146 int i, cycles=0, samples=0;
147 // how many sample points fit in 16 cycles of each frequency
148 DWORD sampleslo = (FSAMPLE<<4)/FREQLO, sampleshi = (FSAMPLE<<4)/FREQHI;
149 // when to tell if we're close enough to one freq or another
150 DWORD threshold = (sampleslo - sampleshi + 1)>>1;
151
152 // TI tags charge at 134.2Khz
153 FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz
154
155 // Place FPGA in passthrough mode, in this mode the CROSS_LO line
156 // connects to SSP_DIN and the SSP_DOUT logic level controls
157 // whether we're modulating the antenna (high)
158 // or listening to the antenna (low)
159 FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_PASSTHRU);
160
161 // get TI tag data into the buffer
162 AcquireTiType();
163
164 FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
165
166 for (i=0; i<n-1; i++) {
167 // count cycles by looking for lo to hi zero crossings
168 if ( (dest[i]<0) && (dest[i+1]>0) ) {
169 cycles++;
170 // after 16 cycles, measure the frequency
171 if (cycles>15) {
172 cycles=0;
173 samples=i-samples; // number of samples in these 16 cycles
174
175 // TI bits are coming to us lsb first so shift them
176 // right through our 128 bit right shift register
177 shift0 = (shift0>>1) | (shift1 << 31);
178 shift1 = (shift1>>1) | (shift2 << 31);
179 shift2 = (shift2>>1) | (shift3 << 31);
180 shift3 >>= 1;
181
182 // check if the cycles fall close to the number
183 // expected for either the low or high frequency
184 if ( (samples>(sampleslo-threshold)) && (samples<(sampleslo+threshold)) ) {
185 // low frequency represents a 1
186 shift3 |= (1<<31);
187 } else if ( (samples>(sampleshi-threshold)) && (samples<(sampleshi+threshold)) ) {
188 // high frequency represents a 0
189 } else {
190 // probably detected a gay waveform or noise
191 // use this as gaydar or discard shift register and start again
192 shift3 = shift2 = shift1 = shift0 = 0;
193 }
194 samples = i;
195
196 // for each bit we receive, test if we've detected a valid tag
197
198 // if we see 17 zeroes followed by 6 ones, we might have a tag
199 // remember the bits are backwards
200 if ( ((shift0 & 0x7fffff) == 0x7e0000) ) {
201 // if start and end bytes match, we have a tag so break out of the loop
202 if ( ((shift0>>16)&0xff) == ((shift3>>8)&0xff) ) {
203 cycles = 0xF0B; //use this as a flag (ugly but whatever)
204 break;
205 }
206 }
207 }
208 }
209 }
210
211 // if flag is set we have a tag
212 if (cycles!=0xF0B) {
213 DbpString("Info: No valid tag detected.");
214 } else {
215 // put 64 bit data into shift1 and shift0
216 shift0 = (shift0>>24) | (shift1 << 8);
217 shift1 = (shift1>>24) | (shift2 << 8);
218
219 // align 16 bit crc into lower half of shift2
220 shift2 = ((shift2>>24) | (shift3 << 8)) & 0x0ffff;
221
222 // if r/w tag, check ident match
223 if ( shift3&(1<<15) ) {
224 DbpString("Info: TI tag is rewriteable");
225 // only 15 bits compare, last bit of ident is not valid
226 if ( ((shift3>>16)^shift0)&0x7fff ) {
227 DbpString("Error: Ident mismatch!");
228 } else {
229 DbpString("Info: TI tag ident is valid");
230 }
231 } else {
232 DbpString("Info: TI tag is readonly");
233 }
234
235 // WARNING the order of the bytes in which we calc crc below needs checking
236 // i'm 99% sure the crc algorithm is correct, but it may need to eat the
237 // bytes in reverse or something
238 // calculate CRC
239 DWORD crc=0;
240
241 crc = update_crc16(crc, (shift0)&0xff);
242 crc = update_crc16(crc, (shift0>>8)&0xff);
243 crc = update_crc16(crc, (shift0>>16)&0xff);
244 crc = update_crc16(crc, (shift0>>24)&0xff);
245 crc = update_crc16(crc, (shift1)&0xff);
246 crc = update_crc16(crc, (shift1>>8)&0xff);
247 crc = update_crc16(crc, (shift1>>16)&0xff);
248 crc = update_crc16(crc, (shift1>>24)&0xff);
249
250 Dbprintf("Info: Tag data: %x%08x, crc=%x",
251 (unsigned int)shift1, (unsigned int)shift0, (unsigned int)shift2 & 0xFFFF);
252 if (crc != (shift2&0xffff)) {
253 Dbprintf("Error: CRC mismatch, expected %x", (unsigned int)crc);
254 } else {
255 DbpString("Info: CRC is good");
256 }
257 }
258 }
259
260 void WriteTIbyte(BYTE b)
261 {
262 int i = 0;
263
264 // modulate 8 bits out to the antenna
265 for (i=0; i<8; i++)
266 {
267 if (b&(1<<i)) {
268 // stop modulating antenna
269 LOW(GPIO_SSC_DOUT);
270 SpinDelayUs(1000);
271 // modulate antenna
272 HIGH(GPIO_SSC_DOUT);
273 SpinDelayUs(1000);
274 } else {
275 // stop modulating antenna
276 LOW(GPIO_SSC_DOUT);
277 SpinDelayUs(300);
278 // modulate antenna
279 HIGH(GPIO_SSC_DOUT);
280 SpinDelayUs(1700);
281 }
282 }
283 }
284
285 void AcquireTiType(void)
286 {
287 int i, j, n;
288 // tag transmission is <20ms, sampling at 2M gives us 40K samples max
289 // each sample is 1 bit stuffed into a DWORD so we need 1250 DWORDS
290 #define TIBUFLEN 1250
291
292 // clear buffer
293 memset(BigBuf,0,sizeof(BigBuf));
294
295 // Set up the synchronous serial port
296 AT91C_BASE_PIOA->PIO_PDR = GPIO_SSC_DIN;
297 AT91C_BASE_PIOA->PIO_ASR = GPIO_SSC_DIN;
298
299 // steal this pin from the SSP and use it to control the modulation
300 AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;
301 AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
302
303 AT91C_BASE_SSC->SSC_CR = AT91C_SSC_SWRST;
304 AT91C_BASE_SSC->SSC_CR = AT91C_SSC_RXEN | AT91C_SSC_TXEN;
305
306 // Sample at 2 Mbit/s, so TI tags are 16.2 vs. 14.9 clocks long
307 // 48/2 = 24 MHz clock must be divided by 12
308 AT91C_BASE_SSC->SSC_CMR = 12;
309
310 AT91C_BASE_SSC->SSC_RCMR = SSC_CLOCK_MODE_SELECT(0);
311 AT91C_BASE_SSC->SSC_RFMR = SSC_FRAME_MODE_BITS_IN_WORD(32) | AT91C_SSC_MSBF;
312 AT91C_BASE_SSC->SSC_TCMR = 0;
313 AT91C_BASE_SSC->SSC_TFMR = 0;
314
315 LED_D_ON();
316
317 // modulate antenna
318 HIGH(GPIO_SSC_DOUT);
319
320 // Charge TI tag for 50ms.
321 SpinDelay(50);
322
323 // stop modulating antenna and listen
324 LOW(GPIO_SSC_DOUT);
325
326 LED_D_OFF();
327
328 i = 0;
329 for(;;) {
330 if(AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY) {
331 BigBuf[i] = AT91C_BASE_SSC->SSC_RHR; // store 32 bit values in buffer
332 i++; if(i >= TIBUFLEN) break;
333 }
334 WDT_HIT();
335 }
336
337 // return stolen pin to SSP
338 AT91C_BASE_PIOA->PIO_PDR = GPIO_SSC_DOUT;
339 AT91C_BASE_PIOA->PIO_ASR = GPIO_SSC_DIN | GPIO_SSC_DOUT;
340
341 char *dest = (char *)BigBuf;
342 n = TIBUFLEN*32;
343 // unpack buffer
344 for (i=TIBUFLEN-1; i>=0; i--) {
345 for (j=0; j<32; j++) {
346 if(BigBuf[i] & (1 << j)) {
347 dest[--n] = 1;
348 } else {
349 dest[--n] = -1;
350 }
351 }
352 }
353 }
354
355 // arguments: 64bit data split into 32bit idhi:idlo and optional 16bit crc
356 // if crc provided, it will be written with the data verbatim (even if bogus)
357 // if not provided a valid crc will be computed from the data and written.
358 void WriteTItag(DWORD idhi, DWORD idlo, WORD crc)
359 {
360 if(crc == 0) {
361 crc = update_crc16(crc, (idlo)&0xff);
362 crc = update_crc16(crc, (idlo>>8)&0xff);
363 crc = update_crc16(crc, (idlo>>16)&0xff);
364 crc = update_crc16(crc, (idlo>>24)&0xff);
365 crc = update_crc16(crc, (idhi)&0xff);
366 crc = update_crc16(crc, (idhi>>8)&0xff);
367 crc = update_crc16(crc, (idhi>>16)&0xff);
368 crc = update_crc16(crc, (idhi>>24)&0xff);
369 }
370 Dbprintf("Writing to tag: %x%08x, crc=%x",
371 (unsigned int) idhi, (unsigned int) idlo, crc);
372
373 // TI tags charge at 134.2Khz
374 FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz
375 // Place FPGA in passthrough mode, in this mode the CROSS_LO line
376 // connects to SSP_DIN and the SSP_DOUT logic level controls
377 // whether we're modulating the antenna (high)
378 // or listening to the antenna (low)
379 FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_PASSTHRU);
380 LED_A_ON();
381
382 // steal this pin from the SSP and use it to control the modulation
383 AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT;
384 AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
385
386 // writing algorithm:
387 // a high bit consists of a field off for 1ms and field on for 1ms
388 // a low bit consists of a field off for 0.3ms and field on for 1.7ms
389 // initiate a charge time of 50ms (field on) then immediately start writing bits
390 // start by writing 0xBB (keyword) and 0xEB (password)
391 // then write 80 bits of data (or 64 bit data + 16 bit crc if you prefer)
392 // finally end with 0x0300 (write frame)
393 // all data is sent lsb firts
394 // finish with 15ms programming time
395
396 // modulate antenna
397 HIGH(GPIO_SSC_DOUT);
398 SpinDelay(50); // charge time
399
400 WriteTIbyte(0xbb); // keyword
401 WriteTIbyte(0xeb); // password
402 WriteTIbyte( (idlo )&0xff );
403 WriteTIbyte( (idlo>>8 )&0xff );
404 WriteTIbyte( (idlo>>16)&0xff );
405 WriteTIbyte( (idlo>>24)&0xff );
406 WriteTIbyte( (idhi )&0xff );
407 WriteTIbyte( (idhi>>8 )&0xff );
408 WriteTIbyte( (idhi>>16)&0xff );
409 WriteTIbyte( (idhi>>24)&0xff ); // data hi to lo
410 WriteTIbyte( (crc )&0xff ); // crc lo
411 WriteTIbyte( (crc>>8 )&0xff ); // crc hi
412 WriteTIbyte(0x00); // write frame lo
413 WriteTIbyte(0x03); // write frame hi
414 HIGH(GPIO_SSC_DOUT);
415 SpinDelay(50); // programming time
416
417 LED_A_OFF();
418
419 // get TI tag data into the buffer
420 AcquireTiType();
421
422 FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
423 DbpString("Now use tiread to check");
424 }
425
426 void SimulateTagLowFrequency(int period, int gap, int ledcontrol)
427 {
428 int i;
429 BYTE *tab = (BYTE *)BigBuf;
430
431 FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_SIMULATOR);
432
433 AT91C_BASE_PIOA->PIO_PER = GPIO_SSC_DOUT | GPIO_SSC_CLK;
434
435 AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
436 AT91C_BASE_PIOA->PIO_ODR = GPIO_SSC_CLK;
437
438 #define SHORT_COIL() LOW(GPIO_SSC_DOUT)
439 #define OPEN_COIL() HIGH(GPIO_SSC_DOUT)
440
441 i = 0;
442 for(;;) {
443 while(!(AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_CLK)) {
444 if(BUTTON_PRESS()) {
445 DbpString("Stopped");
446 return;
447 }
448 WDT_HIT();
449 }
450
451 if (ledcontrol)
452 LED_D_ON();
453
454 if(tab[i])
455 OPEN_COIL();
456 else
457 SHORT_COIL();
458
459 if (ledcontrol)
460 LED_D_OFF();
461
462 while(AT91C_BASE_PIOA->PIO_PDSR & GPIO_SSC_CLK) {
463 if(BUTTON_PRESS()) {
464 DbpString("Stopped");
465 return;
466 }
467 WDT_HIT();
468 }
469
470 i++;
471 if(i == period) {
472 i = 0;
473 if (gap) {
474 SHORT_COIL();
475 SpinDelayUs(gap);
476 }
477 }
478 }
479 }
480
481 /* Provides a framework for bidirectional LF tag communication
482 * Encoding is currently Hitag2, but the general idea can probably
483 * be transferred to other encodings.
484 *
485 * The new FPGA code will, for the LF simulator mode, give on SSC_FRAME
486 * (PA15) a thresholded version of the signal from the ADC. Setting the
487 * ADC path to the low frequency peak detection signal, will enable a
488 * somewhat reasonable receiver for modulation on the carrier signal
489 * that is generated by the reader. The signal is low when the reader
490 * field is switched off, and high when the reader field is active. Due
491 * to the way that the signal looks like, mostly only the rising edge is
492 * useful, your mileage may vary.
493 *
494 * Neat perk: PA15 can not only be used as a bit-banging GPIO, but is also
495 * TIOA1, which can be used as the capture input for timer 1. This should
496 * make it possible to measure the exact edge-to-edge time, without processor
497 * intervention.
498 *
499 * Arguments: divisor is the divisor to be sent to the FPGA (e.g. 95 for 125kHz)
500 * t0 is the carrier frequency cycle duration in terms of MCK (384 for 125kHz)
501 *
502 * The following defines are in carrier periods:
503 */
504 #define HITAG_T_0_MIN 15 /* T[0] should be 18..22 */
505 #define HITAG_T_1_MIN 24 /* T[1] should be 26..30 */
506 #define HITAG_T_EOF 40 /* T_EOF should be > 36 */
507 #define HITAG_T_WRESP 208 /* T_wresp should be 204..212 */
508
509 static void hitag_handle_frame(int t0, int frame_len, char *frame);
510 //#define DEBUG_RA_VALUES 1
511 #define DEBUG_FRAME_CONTENTS 1
512 void SimulateTagLowFrequencyBidir(int divisor, int t0)
513 {
514 #if DEBUG_RA_VALUES || DEBUG_FRAME_CONTENTS
515 int i = 0;
516 #endif
517 char frame[10];
518 int frame_pos=0;
519
520 DbpString("Starting Hitag2 emulator, press button to end");
521 hitag2_init();
522
523 /* Set up simulator mode, frequency divisor which will drive the FPGA
524 * and analog mux selection.
525 */
526 FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_SIMULATOR);
527 FpgaSendCommand(FPGA_CMD_SET_DIVISOR, divisor);
528 SetAdcMuxFor(GPIO_MUXSEL_LOPKD);
529 RELAY_OFF();
530
531 /* Set up Timer 1:
532 * Capture mode, timer source MCK/2 (TIMER_CLOCK1), TIOA is external trigger,
533 * external trigger rising edge, load RA on rising edge of TIOA, load RB on rising
534 * edge of TIOA. Assign PA15 to TIOA1 (peripheral B)
535 */
536
537 AT91C_BASE_PMC->PMC_PCER = (1 << AT91C_ID_TC1);
538 AT91C_BASE_PIOA->PIO_BSR = GPIO_SSC_FRAME;
539 AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKDIS;
540 AT91C_BASE_TC1->TC_CMR = TC_CMR_TCCLKS_TIMER_CLOCK1 |
541 AT91C_TC_ETRGEDG_RISING |
542 AT91C_TC_ABETRG |
543 AT91C_TC_LDRA_RISING |
544 AT91C_TC_LDRB_RISING;
545 AT91C_BASE_TC1->TC_CCR = AT91C_TC_CLKEN |
546 AT91C_TC_SWTRG;
547
548 /* calculate the new value for the carrier period in terms of TC1 values */
549 t0 = t0/2;
550
551 int overflow = 0;
552 while(!BUTTON_PRESS()) {
553 WDT_HIT();
554 if(AT91C_BASE_TC1->TC_SR & AT91C_TC_LDRAS) {
555 int ra = AT91C_BASE_TC1->TC_RA;
556 if((ra > t0*HITAG_T_EOF) | overflow) ra = t0*HITAG_T_EOF+1;
557 #if DEBUG_RA_VALUES
558 if(ra > 255 || overflow) ra = 255;
559 ((char*)BigBuf)[i] = ra;
560 i = (i+1) % 8000;
561 #endif
562
563 if(overflow || (ra > t0*HITAG_T_EOF) || (ra < t0*HITAG_T_0_MIN)) {
564 /* Ignore */
565 } else if(ra >= t0*HITAG_T_1_MIN ) {
566 /* '1' bit */
567 if(frame_pos < 8*sizeof(frame)) {
568 frame[frame_pos / 8] |= 1<<( 7-(frame_pos%8) );
569 frame_pos++;
570 }
571 } else if(ra >= t0*HITAG_T_0_MIN) {
572 /* '0' bit */
573 if(frame_pos < 8*sizeof(frame)) {
574 frame[frame_pos / 8] |= 0<<( 7-(frame_pos%8) );
575 frame_pos++;
576 }
577 }
578
579 overflow = 0;
580 LED_D_ON();
581 } else {
582 if(AT91C_BASE_TC1->TC_CV > t0*HITAG_T_EOF) {
583 /* Minor nuisance: In Capture mode, the timer can not be
584 * stopped by a Compare C. There's no way to stop the clock
585 * in software, so we'll just have to note the fact that an
586 * overflow happened and the next loaded timer value might
587 * have wrapped. Also, this marks the end of frame, and the
588 * still running counter can be used to determine the correct
589 * time for the start of the reply.
590 */
591 overflow = 1;
592
593 if(frame_pos > 0) {
594 /* Have a frame, do something with it */
595 #if DEBUG_FRAME_CONTENTS
596 ((char*)BigBuf)[i++] = frame_pos;
597 memcpy( ((char*)BigBuf)+i, frame, 7);
598 i+=7;
599 i = i % sizeof(BigBuf);
600 #endif
601 hitag_handle_frame(t0, frame_pos, frame);
602 memset(frame, 0, sizeof(frame));
603 }
604 frame_pos = 0;
605
606 }
607 LED_D_OFF();
608 }
609 }
610 DbpString("All done");
611 }
612
613 static void hitag_send_bit(int t0, int bit) {
614 if(bit == 1) {
615 /* Manchester: Loaded, then unloaded */
616 LED_A_ON();
617 SHORT_COIL();
618 while(AT91C_BASE_TC1->TC_CV < t0*15);
619 OPEN_COIL();
620 while(AT91C_BASE_TC1->TC_CV < t0*31);
621 LED_A_OFF();
622 } else if(bit == 0) {
623 /* Manchester: Unloaded, then loaded */
624 LED_B_ON();
625 OPEN_COIL();
626 while(AT91C_BASE_TC1->TC_CV < t0*15);
627 SHORT_COIL();
628 while(AT91C_BASE_TC1->TC_CV < t0*31);
629 LED_B_OFF();
630 }
631 AT91C_BASE_TC1->TC_CCR = AT91C_TC_SWTRG; /* Reset clock for the next bit */
632
633 }
634 static void hitag_send_frame(int t0, int frame_len, const char const * frame, int fdt)
635 {
636 OPEN_COIL();
637 AT91C_BASE_PIOA->PIO_OER = GPIO_SSC_DOUT;
638
639 /* Wait for HITAG_T_WRESP carrier periods after the last reader bit,
640 * not that since the clock counts since the rising edge, but T_wresp is
641 * with respect to the falling edge, we need to wait actually (T_wresp - T_g)
642 * periods. The gap time T_g varies (4..10).
643 */
644 while(AT91C_BASE_TC1->TC_CV < t0*(fdt-8));
645
646 int saved_cmr = AT91C_BASE_TC1->TC_CMR;
647 AT91C_BASE_TC1->TC_CMR &= ~AT91C_TC_ETRGEDG; /* Disable external trigger for the clock */
648 AT91C_BASE_TC1->TC_CCR = AT91C_TC_SWTRG; /* Reset the clock and use it for response timing */
649
650 int i;
651 for(i=0; i<5; i++)
652 hitag_send_bit(t0, 1); /* Start of frame */
653
654 for(i=0; i<frame_len; i++) {
655 hitag_send_bit(t0, !!(frame[i/ 8] & (1<<( 7-(i%8) ))) );
656 }
657
658 OPEN_COIL();
659 AT91C_BASE_TC1->TC_CMR = saved_cmr;
660 }
661
662 /* Callback structure to cleanly separate tag emulation code from the radio layer. */
663 static int hitag_cb(const char* response_data, const int response_length, const int fdt, void *cb_cookie)
664 {
665 hitag_send_frame(*(int*)cb_cookie, response_length, response_data, fdt);
666 return 0;
667 }
668 /* Frame length in bits, frame contents in MSBit first format */
669 static void hitag_handle_frame(int t0, int frame_len, char *frame)
670 {
671 hitag2_handle_command(frame, frame_len, hitag_cb, &t0);
672 }
673
674 // compose fc/8 fc/10 waveform
675 static void fc(int c, int *n) {
676 BYTE *dest = (BYTE *)BigBuf;
677 int idx;
678
679 // for when we want an fc8 pattern every 4 logical bits
680 if(c==0) {
681 dest[((*n)++)]=1;
682 dest[((*n)++)]=1;
683 dest[((*n)++)]=0;
684 dest[((*n)++)]=0;
685 dest[((*n)++)]=0;
686 dest[((*n)++)]=0;
687 dest[((*n)++)]=0;
688 dest[((*n)++)]=0;
689 }
690 // an fc/8 encoded bit is a bit pattern of 11000000 x6 = 48 samples
691 if(c==8) {
692 for (idx=0; idx<6; idx++) {
693 dest[((*n)++)]=1;
694 dest[((*n)++)]=1;
695 dest[((*n)++)]=0;
696 dest[((*n)++)]=0;
697 dest[((*n)++)]=0;
698 dest[((*n)++)]=0;
699 dest[((*n)++)]=0;
700 dest[((*n)++)]=0;
701 }
702 }
703
704 // an fc/10 encoded bit is a bit pattern of 1110000000 x5 = 50 samples
705 if(c==10) {
706 for (idx=0; idx<5; idx++) {
707 dest[((*n)++)]=1;
708 dest[((*n)++)]=1;
709 dest[((*n)++)]=1;
710 dest[((*n)++)]=0;
711 dest[((*n)++)]=0;
712 dest[((*n)++)]=0;
713 dest[((*n)++)]=0;
714 dest[((*n)++)]=0;
715 dest[((*n)++)]=0;
716 dest[((*n)++)]=0;
717 }
718 }
719 }
720
721 // prepare a waveform pattern in the buffer based on the ID given then
722 // simulate a HID tag until the button is pressed
723 void CmdHIDsimTAG(int hi, int lo, int ledcontrol)
724 {
725 int n=0, i=0;
726 /*
727 HID tag bitstream format
728 The tag contains a 44bit unique code. This is sent out MSB first in sets of 4 bits
729 A 1 bit is represented as 6 fc8 and 5 fc10 patterns
730 A 0 bit is represented as 5 fc10 and 6 fc8 patterns
731 A fc8 is inserted before every 4 bits
732 A special start of frame pattern is used consisting a0b0 where a and b are neither 0
733 nor 1 bits, they are special patterns (a = set of 12 fc8 and b = set of 10 fc10)
734 */
735
736 if (hi>0xFFF) {
737 DbpString("Tags can only have 44 bits.");
738 return;
739 }
740 fc(0,&n);
741 // special start of frame marker containing invalid bit sequences
742 fc(8, &n); fc(8, &n); // invalid
743 fc(8, &n); fc(10, &n); // logical 0
744 fc(10, &n); fc(10, &n); // invalid
745 fc(8, &n); fc(10, &n); // logical 0
746
747 WDT_HIT();
748 // manchester encode bits 43 to 32
749 for (i=11; i>=0; i--) {
750 if ((i%4)==3) fc(0,&n);
751 if ((hi>>i)&1) {
752 fc(10, &n); fc(8, &n); // low-high transition
753 } else {
754 fc(8, &n); fc(10, &n); // high-low transition
755 }
756 }
757
758 WDT_HIT();
759 // manchester encode bits 31 to 0
760 for (i=31; i>=0; i--) {
761 if ((i%4)==3) fc(0,&n);
762 if ((lo>>i)&1) {
763 fc(10, &n); fc(8, &n); // low-high transition
764 } else {
765 fc(8, &n); fc(10, &n); // high-low transition
766 }
767 }
768
769 if (ledcontrol)
770 LED_A_ON();
771 SimulateTagLowFrequency(n, 0, ledcontrol);
772
773 if (ledcontrol)
774 LED_A_OFF();
775 }
776
777
778 // loop to capture raw HID waveform then FSK demodulate the TAG ID from it
779 void CmdHIDdemodFSK(int findone, int *high, int *low, int ledcontrol)
780 {
781 BYTE *dest = (BYTE *)BigBuf;
782 int m=0, n=0, i=0, idx=0, found=0, lastval=0;
783 DWORD hi=0, lo=0;
784
785 FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz
786 FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_READER);
787
788 // Connect the A/D to the peak-detected low-frequency path.
789 SetAdcMuxFor(GPIO_MUXSEL_LOPKD);
790
791 // Give it a bit of time for the resonant antenna to settle.
792 SpinDelay(50);
793
794 // Now set up the SSC to get the ADC samples that are now streaming at us.
795 FpgaSetupSsc();
796
797 for(;;) {
798 WDT_HIT();
799 if (ledcontrol)
800 LED_A_ON();
801 if(BUTTON_PRESS()) {
802 DbpString("Stopped");
803 if (ledcontrol)
804 LED_A_OFF();
805 return;
806 }
807
808 i = 0;
809 m = sizeof(BigBuf);
810 memset(dest,128,m);
811 for(;;) {
812 if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_TXRDY)) {
813 AT91C_BASE_SSC->SSC_THR = 0x43;
814 if (ledcontrol)
815 LED_D_ON();
816 }
817 if(AT91C_BASE_SSC->SSC_SR & (AT91C_SSC_RXRDY)) {
818 dest[i] = (BYTE)AT91C_BASE_SSC->SSC_RHR;
819 // we don't care about actual value, only if it's more or less than a
820 // threshold essentially we capture zero crossings for later analysis
821 if(dest[i] < 127) dest[i] = 0; else dest[i] = 1;
822 i++;
823 if (ledcontrol)
824 LED_D_OFF();
825 if(i >= m) {
826 break;
827 }
828 }
829 }
830
831 // FSK demodulator
832
833 // sync to first lo-hi transition
834 for( idx=1; idx<m; idx++) {
835 if (dest[idx-1]<dest[idx])
836 lastval=idx;
837 break;
838 }
839 WDT_HIT();
840
841 // count cycles between consecutive lo-hi transitions, there should be either 8 (fc/8)
842 // or 10 (fc/10) cycles but in practice due to noise etc we may end up with with anywhere
843 // between 7 to 11 cycles so fuzz it by treat anything <9 as 8 and anything else as 10
844 for( i=0; idx<m; idx++) {
845 if (dest[idx-1]<dest[idx]) {
846 dest[i]=idx-lastval;
847 if (dest[i] <= 8) {
848 dest[i]=1;
849 } else {
850 dest[i]=0;
851 }
852
853 lastval=idx;
854 i++;
855 }
856 }
857 m=i;
858 WDT_HIT();
859
860 // we now have a set of cycle counts, loop over previous results and aggregate data into bit patterns
861 lastval=dest[0];
862 idx=0;
863 i=0;
864 n=0;
865 for( idx=0; idx<m; idx++) {
866 if (dest[idx]==lastval) {
867 n++;
868 } else {
869 // a bit time is five fc/10 or six fc/8 cycles so figure out how many bits a pattern width represents,
870 // an extra fc/8 pattern preceeds every 4 bits (about 200 cycles) just to complicate things but it gets
871 // swallowed up by rounding
872 // expected results are 1 or 2 bits, any more and it's an invalid manchester encoding
873 // special start of frame markers use invalid manchester states (no transitions) by using sequences
874 // like 111000
875 if (dest[idx-1]) {
876 n=(n+1)/6; // fc/8 in sets of 6
877 } else {
878 n=(n+1)/5; // fc/10 in sets of 5
879 }
880 switch (n) { // stuff appropriate bits in buffer
881 case 0:
882 case 1: // one bit
883 dest[i++]=dest[idx-1];
884 break;
885 case 2: // two bits
886 dest[i++]=dest[idx-1];
887 dest[i++]=dest[idx-1];
888 break;
889 case 3: // 3 bit start of frame markers
890 dest[i++]=dest[idx-1];
891 dest[i++]=dest[idx-1];
892 dest[i++]=dest[idx-1];
893 break;
894 // When a logic 0 is immediately followed by the start of the next transmisson
895 // (special pattern) a pattern of 4 bit duration lengths is created.
896 case 4:
897 dest[i++]=dest[idx-1];
898 dest[i++]=dest[idx-1];
899 dest[i++]=dest[idx-1];
900 dest[i++]=dest[idx-1];
901 break;
902 default: // this shouldn't happen, don't stuff any bits
903 break;
904 }
905 n=0;
906 lastval=dest[idx];
907 }
908 }
909 m=i;
910 WDT_HIT();
911
912 // final loop, go over previously decoded manchester data and decode into usable tag ID
913 // 111000 bit pattern represent start of frame, 01 pattern represents a 1 and 10 represents a 0
914 for( idx=0; idx<m-6; idx++) {
915 // search for a start of frame marker
916 if ( dest[idx] && dest[idx+1] && dest[idx+2] && (!dest[idx+3]) && (!dest[idx+4]) && (!dest[idx+5]) )
917 {
918 found=1;
919 idx+=6;
920 if (found && (hi|lo)) {
921 Dbprintf("TAG ID: %x%08x (%d)",
922 (unsigned int) hi, (unsigned int) lo, (unsigned int) (lo>>1) & 0xFFFF);
923 /* if we're only looking for one tag */
924 if (findone)
925 {
926 *high = hi;
927 *low = lo;
928 return;
929 }
930 hi=0;
931 lo=0;
932 found=0;
933 }
934 }
935 if (found) {
936 if (dest[idx] && (!dest[idx+1]) ) {
937 hi=(hi<<1)|(lo>>31);
938 lo=(lo<<1)|0;
939 } else if ( (!dest[idx]) && dest[idx+1]) {
940 hi=(hi<<1)|(lo>>31);
941 lo=(lo<<1)|1;
942 } else {
943 found=0;
944 hi=0;
945 lo=0;
946 }
947 idx++;
948 }
949 if ( dest[idx] && dest[idx+1] && dest[idx+2] && (!dest[idx+3]) && (!dest[idx+4]) && (!dest[idx+5]) )
950 {
951 found=1;
952 idx+=6;
953 if (found && (hi|lo)) {
954 Dbprintf("TAG ID: %x%08x (%d)",
955 (unsigned int) hi, (unsigned int) lo, (unsigned int) (lo>>1) & 0xFFFF);
956 /* if we're only looking for one tag */
957 if (findone)
958 {
959 *high = hi;
960 *low = lo;
961 return;
962 }
963 hi=0;
964 lo=0;
965 found=0;
966 }
967 }
968 }
969 WDT_HIT();
970 }
971 }
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