fix 'hf iclass sim'

* fix tag response timing. iClass differs from ISO15693 in this respect.
* speedup CodeIso15693AsTag()
* TransmitTo15693Tag(): don't send unmodulated start of SOF
* reduce modulation depth in hi_simulate.v
* calculate CRC for configuration block when simulating
* Show real response time instead of planned response time in 'hf list iclass'

armsrc/iclass.c

@@ -59,6 +59,13 @@
 
 static int timeout = 4096;
 
+// iCLASS has a slightly different timing compared to ISO15693. According to the picopass data sheet the tag response is expected 330us after
+// the reader command. This is measured from end of reader EOF to first modulation of the tag's SOF which starts with a 56,64us unmodulated period.
+// 330us = 140 ssp_clk cycles @ 423,75kHz when simulating.
+// 56,64us = 24 ssp_clk_cycles
+#define DELAY_ICLASS_VCD_TO_VICC_SIM 140
+#define TAG_SOF_UNMODULATED          24
+
 //-----------------------------------------------------------------------------
 // The software UART that receives commands from the reader, and its state
 // variables.
@@ -800,13 +807,12 @@ int doIClassSimulation(int simulationMode, uint8_t *reader_mac_buf) {
 	AppendCrc(anticoll_data, 8);
 	AppendCrc(csn_data, 8);
 
-	uint8_t diversified_key_d[8];
+	uint8_t diversified_key_d[8] = { 0x00 };
-	uint8_t diversified_key_c[8];
+	uint8_t diversified_key_c[8] = { 0x00 };
 	uint8_t *diversified_key = diversified_key_d;
 
 	// configuration block
 	uint8_t conf_block[10] = {0x12, 0xFF, 0xFF, 0xFF, 0x7F, 0x1F, 0xFF, 0x3C, 0x00, 0x00};
-	AppendCrc(conf_block, 8);
 
 	// e-Purse
 	uint8_t card_challenge_data[8] = { 0xfe, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
@@ -819,6 +825,8 @@ int doIClassSimulation(int simulationMode, uint8_t *reader_mac_buf) {
 		memcpy(diversified_key_c, emulator + 8 * 4, 8);   // Kc
 	}
 
+	AppendCrc(conf_block, 8);
+
 	// save card challenge for sim2,4 attack
 	if (reader_mac_buf != NULL) {
 		memcpy(reader_mac_buf, card_challenge_data, 8);
@@ -1185,7 +1193,7 @@ int doIClassSimulation(int simulationMode, uint8_t *reader_mac_buf) {
 		} else if (receivedCmd[0] == ICLASS_CMD_PAGESEL && len == 4) {
 			// Pagesel
 			// Chips with a single page will not answer to this command
-			// Otherwise, we should answer 8bytes (block) + 2bytes CRC
+			// Otherwise, we should answer 8bytes (conf block 1) + 2bytes CRC
 			if (chip_state == SELECTED) {
 				if (simulationMode == ICLASS_SIM_MODE_FULL && max_page > 0) {
 					current_page = receivedCmd[1];
@@ -1219,11 +1227,11 @@ int doIClassSimulation(int simulationMode, uint8_t *reader_mac_buf) {
 		}
 
 		/**
-		A legit tag has about 311,5us delay between reader EOT and tag SOF.
+		A legit tag has about 273,4us delay between reader EOT and tag SOF.
 		**/
 		if (modulated_response_size > 0) {
-			uint32_t response_time = reader_eof_time + DELAY_ISO15693_VCD_TO_VICC_SIM - DELAY_ARM_TO_READER_SIM;
+			uint32_t response_time = reader_eof_time + DELAY_ICLASS_VCD_TO_VICC_SIM - TAG_SOF_UNMODULATED - DELAY_ARM_TO_READER_SIM;
-			TransmitTo15693Reader(modulated_response, modulated_response_size, response_time, false);
+			TransmitTo15693Reader(modulated_response, modulated_response_size, &response_time, 0, false);
 			LogTrace(trace_data, trace_data_size, response_time + DELAY_ARM_TO_READER_SIM, response_time + (modulated_response_size << 6) + DELAY_ARM_TO_READER_SIM, NULL, false);
 		}
 
@@ -1559,6 +1567,7 @@ static uint8_t handshakeIclassTag_ext(uint8_t *card_data, bool use_credit_key) {
 	ReaderTransmitIClass(act_all, 1);
 	// Card present?
 	if (!ReaderReceiveIClass(resp)) return read_status;//Fail
+
 	//Send Identify
 	ReaderTransmitIClass(identify, 1);
 	//We expect a 10-byte response here, 8 byte anticollision-CSN and 2 byte CRC

armsrc/iso15693.c

@@ -246,6 +246,8 @@ static void CodeIso15693AsReader256(uint8_t *cmd, int n)
 	// }
 // }
 
+static const uint8_t encode_4bits[16] = { 0xaa, 0x6a, 0x9a, 0x5a, 0xa6, 0x66, 0x96, 0x56, 0xa9, 0x69, 0x99, 0x59, 0xa5, 0x65, 0x95, 0x55 };
+
 void CodeIso15693AsTag(uint8_t *cmd, size_t len) {
 	/*
 	 * SOF comprises 3 parts;
@@ -281,15 +283,8 @@ void CodeIso15693AsTag(uint8_t *cmd, size_t len) {
 
 	// data
 	for (int i = 0; i < len; i++) {
-		for(int j = 0; j < 8; j++) {
+		ToSend[++ToSendMax] = encode_4bits[cmd[i] & 0xF];
-			if ((cmd[i] >> j) & 0x01) {
+		ToSend[++ToSendMax] = encode_4bits[cmd[i] >> 4];
-					ToSendStuffBit(0);
-					ToSendStuffBit(1);
-			} else {
-					ToSendStuffBit(1);
-					ToSendStuffBit(0);
-			}
-		}
 	}
 
 	// EOF
@@ -327,19 +322,32 @@ static void TransmitTo15693Tag(const uint8_t *cmd, int len, uint32_t start_time)
 //-----------------------------------------------------------------------------
 // Transmit the tag response (to the reader) that was placed in cmd[].
 //-----------------------------------------------------------------------------
-void TransmitTo15693Reader(const uint8_t *cmd, size_t len, uint32_t start_time, bool slow) {
+void TransmitTo15693Reader(const uint8_t *cmd, size_t len, uint32_t *start_time, uint32_t slot_time, bool slow) {
 	// don't use the FPGA_HF_SIMULATOR_MODULATE_424K_8BIT minor mode. It would spoil GetCountSspClk()
 	FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_SIMULATOR | FPGA_HF_SIMULATOR_MODULATE_424K);
 
-	uint8_t shift_delay = start_time & 0x00000007;
+	uint32_t modulation_start_time = *start_time + 3 * 8;  // no need to transfer the unmodulated start of SOF
 	
-	while (GetCountSspClk() < (start_time & 0xfffffff8)) ;
+	while (GetCountSspClk() > (modulation_start_time & 0xfffffff8) + 3) { // we will miss the intended time
+		if (slot_time) {
+			modulation_start_time += slot_time; // use next available slot
+		} else {
+			modulation_start_time = (modulation_start_time & 0xfffffff8) + 8; // next possible time
+		}
+	}
+
+	while (GetCountSspClk() < (modulation_start_time & 0xfffffff8)) 
+		/* wait */ ;
+
+	uint8_t shift_delay = modulation_start_time & 0x00000007;
+
+	*start_time = modulation_start_time - 3 * 8;
 
 	LED_C_ON();
 	uint8_t bits_to_shift = 0x00;
 	uint8_t bits_to_send = 0x00;
 	for (size_t c = 0; c < len; c++) {
-		for (int i = 7; i >= 0; i--) {
+		for (int i = (c==0?4:7); i >= 0; i--) {
 			uint8_t cmd_bits = ((cmd[c] >> i) & 0x01) ? 0xff : 0x00;
 			for (int j = 0; j < (slow?4:1); ) {
 				if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXRDY) {
@@ -361,7 +369,6 @@ void TransmitTo15693Reader(const uint8_t *cmd, size_t len, uint32_t start_time,
 		}
 	}
 	LED_C_OFF();
-
 }
 
 
@@ -1529,7 +1536,7 @@ void SimTagIso15693(uint32_t parameter, uint8_t *uid)
 		if ((cmd_len >= 5) && (cmd[0] & ISO15693_REQ_INVENTORY) && (cmd[1] == ISO15693_INVENTORY)) { // TODO: check more flags
 			bool slow = !(cmd[0] & ISO15693_REQ_DATARATE_HIGH);
 			start_time = eof_time + DELAY_ISO15693_VCD_TO_VICC_SIM - DELAY_ARM_TO_READER_SIM;
-			TransmitTo15693Reader(ToSend, ToSendMax, start_time, slow);
+			TransmitTo15693Reader(ToSend, ToSendMax, &start_time, 0, slow);
 		}
 
 		Dbprintf("%d bytes read from reader:", cmd_len);

armsrc/iso15693.h

@@ -26,7 +26,7 @@
 
 void CodeIso15693AsTag(uint8_t *cmd, size_t len);
 int GetIso15693CommandFromReader(uint8_t *received, size_t max_len, uint32_t *eof_time);
-void TransmitTo15693Reader(const uint8_t *cmd, size_t len, uint32_t start_time, bool slow);
+void TransmitTo15693Reader(const uint8_t *cmd, size_t len, uint32_t *start_time, uint32_t slot_time, bool slow);
 void SnoopIso15693(void);
 void AcquireRawAdcSamplesIso15693(void);
 void ReaderIso15693(uint32_t parameter);

fpga/hi_simulate.v

@@ -132,7 +132,7 @@ always @(*)
 // modulation than a real tag would.
 assign pwr_hi = 1'b0;                   // HF antenna connected to GND
 assign pwr_oe3 = 1'b0;                  // 10k Load
-assign pwr_oe1 = modulating_carrier;    // 33 Ohms Load
+assign pwr_oe1 = 1'b0;                  // 33 Ohms Load
 assign pwr_oe4 = modulating_carrier;    // 33 Ohms Load
 
 // This is all LF and doesn't matter