diff --git a/armsrc/appmain.c b/armsrc/appmain.c
index 35c9e5bf..237d3008 100644
--- a/armsrc/appmain.c
+++ b/armsrc/appmain.c
@@ -1055,6 +1055,9 @@ void UsbPacketReceived(uint8_t *packet, int len)
 		case CMD_PCF7931_WRITE:
 			WritePCF7931(c->d.asBytes[0],c->d.asBytes[1],c->d.asBytes[2],c->d.asBytes[3],c->d.asBytes[4],c->d.asBytes[5],c->d.asBytes[6], c->d.asBytes[9], c->d.asBytes[7]-128,c->d.asBytes[8]-128, c->arg[0], c->arg[1], c->arg[2]);
 			break;
+		case CMD_PCF7931_BRUTEFORCE:
+			BruteForcePCF7931(c->arg[0], (c->arg[1] & 0xFF), c->d.asBytes[9], c->d.asBytes[7]-128,c->d.asBytes[8]-128);
+			break;
 		case CMD_EM4X_READ_WORD:
 			EM4xReadWord(c->arg[0], c->arg[1],c->arg[2]);
 			break;
diff --git a/armsrc/pcf7931.c b/armsrc/pcf7931.c
index e4ba1da5..d5f630cc 100644
--- a/armsrc/pcf7931.c
+++ b/armsrc/pcf7931.c
@@ -8,7 +8,7 @@
 #define T0_PCF 8 //period for the pcf7931 in us
 #define ALLOC 16
 
-int DemodPCF7931(uint8_t **outBlocks) {
+size_t DemodPCF7931(uint8_t **outBlocks) {
 
     uint8_t bits[256] = {0x00};
 	uint8_t blocks[8][16];
@@ -18,13 +18,12 @@ int DemodPCF7931(uint8_t **outBlocks) {
 	if (  GraphTraceLen > 18000 )
 		GraphTraceLen = 18000;
 	
-	
 	int i, j, lastval, bitidx, half_switch;
 	int clock = 64;
 	int tolerance = clock / 8;
 	int pmc, block_done;
 	int lc, warnings = 0;
-	int num_blocks = 0;
+	size_t num_blocks = 0;
 	int lmin=128, lmax=128;
 	uint8_t dir;
 	//clear read buffer
@@ -141,136 +140,344 @@ int DemodPCF7931(uint8_t **outBlocks) {
 	return num_blocks;
 }
 
-int IsBlock0PCF7931(uint8_t *Block) {
-	// Assume RFU means 0 :)
-	if((memcmp(Block, "\x00\x00\x00\x00\x00\x00\x00\x01", 8) == 0) && memcmp(Block+9, "\x00\x00\x00\x00\x00\x00\x00", 7) == 0) // PAC enabled
-		return 1;
-	if((memcmp(Block+9, "\x00\x00\x00\x00\x00\x00\x00", 7) == 0) && Block[7] == 0) // PAC disabled, can it *really* happen ?
-		return 1;
+uint8_t IsBlock0PCF7931(uint8_t *block)
+{
+	// assuming all RFU bits are set to 0
+	// if PAC is enabled password is set to 0
+	if (block[7] == 0x01)
+	{
+		if (!memcmp(block, "\x00\x00\x00\x00\x00\x00\x00", 7) && !memcmp(block+9, "\x00\x00\x00\x00\x00\x00\x00", 7))
+			return 1;
+	}
+	else if (block[7] == 0x00)
+	{
+		if (!memcmp(block+9, "\x00\x00\x00\x00\x00\x00\x00", 7))
+			return 1;
+	}
 	return 0;
 }
 
-int IsBlock1PCF7931(uint8_t *Block) {
-	// Assume RFU means 0 :)
-	if(Block[10] == 0 && Block[11] == 0 && Block[12] == 0 && Block[13] == 0)
-		if((Block[14] & 0x7f) <= 9 && Block[15] <= 9)
+uint8_t IsBlock1PCF7931(uint8_t *block) {
+	// assuming all RFU bits are set to 0
+	if (block[10] == 0 && block[11] == 0 && block[12] == 0 && block[13] == 0)
+		if((block[14] & 0x7f) <= 9 && block[15] <= 9)
 			return 1;
 
 	return 0;
 }
 
-void ReadPCF7931() {
-	uint8_t Blocks[8][17];
-	uint8_t tmpBlocks[4][16];
-	int i, j, ind, ind2, n;
-	int num_blocks = 0;
-	int max_blocks = 8;
-	int ident = 0;
-	int error = 0;
-	int tries = 0;
+static inline void print_block(uint8_t *data)
+{
+	Dbprintf("%02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x",
+		data[0], data[1], data[2], data[3], data[4], data[5], data[6], data[7],
+		data[8], data[9], data[10], data[11], data[12], data[13], data[14], data[15]);
+}
 
-	memset(Blocks, 0, 8*17*sizeof(uint8_t));
+void ReadPCF7931()
+{
+	int found_blocks = 0; // successfully read blocks
+	int max_blocks = 8;	// readable blocks	
+	uint8_t memory_blocks[8][17]; // PCF content
+	
+	uint8_t single_blocks[8][17]; // PFC blocks with unknown position
+	int single_blocks_cnt = 0;
 
-	do {
-		memset(tmpBlocks, 0, 4*16*sizeof(uint8_t));
-		n = DemodPCF7931((uint8_t**)tmpBlocks);
+	size_t n = 0; // transmitted blocks	
+	uint8_t tmp_blocks[4][16]; // temporary read buffer
+	
+	uint8_t found_0_1 = 0; // flag: blocks 0 and 1 were found
+	int errors = 0; // error counter
+	int tries = 0; // tries counter
+	
+	memset(memory_blocks, 0, 8*17*sizeof(uint8_t));
+	memset(single_blocks, 0, 8*17*sizeof(uint8_t));
+	
+	int i = 0, j = 0;
+
+	do
+	{
+		i = 0;
+		
+		memset(tmp_blocks, 0, 4*16*sizeof(uint8_t));
+		n = DemodPCF7931((uint8_t**)tmp_blocks);
 		if(!n)
-			error++;
-		if(error==10 && num_blocks == 0) {
+			errors++;
+		
+		// exit if no block is received 
+		if (errors == 10 && found_blocks == 0)
+		{
 			Dbprintf("Error, no tag or bad tag");
 			return;
 		}
-		else if (tries==20 || error==10) {
+		// exit if too many errors during reading
+		else if (tries > 50 && (float)(errors/tries) > .5f)
+		{
 			Dbprintf("Error reading the tag");
 			Dbprintf("Here is the partial content");
 			goto end;
 		}
-
-		for(i=0; i<n; i++)
-			Dbprintf("(dbg) %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x",
-					 tmpBlocks[i][0], tmpBlocks[i][1], tmpBlocks[i][2], tmpBlocks[i][3], tmpBlocks[i][4], tmpBlocks[i][5], tmpBlocks[i][6], tmpBlocks[i][7],
-					tmpBlocks[i][8], tmpBlocks[i][9], tmpBlocks[i][10], tmpBlocks[i][11], tmpBlocks[i][12], tmpBlocks[i][13], tmpBlocks[i][14], tmpBlocks[i][15]);
-		if(!ident) {
-			for(i=0; i<n; i++) {
-				if(IsBlock0PCF7931(tmpBlocks[i])) {
-					// Found block 0 ?
-					if(i < n-1 && IsBlock1PCF7931(tmpBlocks[i+1])) {
-						// Found block 1!
-						// \o/
-						ident = 1;
-						memcpy(Blocks[0], tmpBlocks[i], 16);
-						Blocks[0][ALLOC] = 1;
-						memcpy(Blocks[1], tmpBlocks[i+1], 16);
-						Blocks[1][ALLOC] = 1;
-						max_blocks = MAX((Blocks[1][14] & 0x7f), Blocks[1][15]) + 1;
-						// Debug print
-						Dbprintf("(dbg) Max blocks: %d", max_blocks);
-						num_blocks = 2;
-						// Handle following blocks
-						for(j=i+2, ind2=2; j!=i; j++, ind2++, num_blocks++) {
-							if(j==n) j=0;
-							if(j==i) break;
-							memcpy(Blocks[ind2], tmpBlocks[j], 16);
-							Blocks[ind2][ALLOC] = 1;
-						}
+		
+		// our logic breaks if we don't get at least two blocks
+		if (n < 2)
+		{
+			if (single_blocks_cnt < max_blocks)
+			{
+				for (i = 0; i < single_blocks_cnt; ++i)
+				{
+					if (!memcmp(single_blocks[i], tmp_blocks[0], 16))
+					{
+						j = 1;
 						break;
 					}
 				}
+				if (j != 1)
+				{
+					memcpy(single_blocks[single_blocks_cnt], tmp_blocks[0], 16);
+					single_blocks_cnt++;
+				}
+				j = 0;
+			}
+			continue;
+	 	}
+	 	
+	 	Dbprintf("(dbg) got %d blocks (%d/%d found)", n, found_blocks, (max_blocks == 0 ? found_blocks : max_blocks));
+		
+		i = 0;
+		if(!found_0_1)
+		{			
+			while (i < n - 1)
+			{
+				if (IsBlock0PCF7931(tmp_blocks[i]) && IsBlock1PCF7931(tmp_blocks[i+1]))
+				{
+					found_0_1 = 1;
+					memcpy(memory_blocks[0], tmp_blocks[i], 16);
+					memcpy(memory_blocks[1], tmp_blocks[i+1], 16);
+					memory_blocks[0][ALLOC] = memory_blocks[1][ALLOC] = 1;
+					// block 1 tells how many blocks are going to be sent
+					max_blocks = MAX((memory_blocks[1][14] & 0x7f), memory_blocks[1][15]) + 1;
+					found_blocks = 2;
+					
+					Dbprintf("Found blocks 0 and 1. PCF is transmitting %d blocks.", max_blocks);
+					
+					// handle the following blocks
+					for (j = i + 2; j < n; ++j)
+					{
+						memcpy(memory_blocks[found_blocks], tmp_blocks[j], 16);
+						memory_blocks[found_blocks][ALLOC] = 1;
+						++found_blocks;
+					}
+					break;
+				}
+				++i;
 			}
 		}
-		else {
-			for(i=0; i<n; i++) { // Look for identical block in known blocks
-				if(memcmp(tmpBlocks[i], "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", 16)) { // Block is not full of 00
-					for(j=0; j<max_blocks; j++) {
-						if(Blocks[j][ALLOC] == 1 && !memcmp(tmpBlocks[i], Blocks[j], 16)) {
-							// Found an identical block
-							for(ind=i-1,ind2=j-1; ind >= 0; ind--,ind2--) {
-								if(ind2 < 0)
-									ind2 = max_blocks;
-								if(!Blocks[ind2][ALLOC]) { // Block ind2 not already found
-									// Dbprintf("Tmp %d -> Block %d", ind, ind2);
-									memcpy(Blocks[ind2], tmpBlocks[ind], 16);
-									Blocks[ind2][ALLOC] = 1;
-									num_blocks++;
-									if(num_blocks == max_blocks) goto end;
-								}
-							}
-							for(ind=i+1,ind2=j+1; ind < n; ind++,ind2++) {
-								if(ind2 > max_blocks)
-									ind2 = 0;
-								if(!Blocks[ind2][ALLOC]) { // Block ind2 not already found
-									// Dbprintf("Tmp %d -> Block %d", ind, ind2);
-									memcpy(Blocks[ind2], tmpBlocks[ind], 16);
-									Blocks[ind2][ALLOC] = 1;
-									num_blocks++;
-									if(num_blocks == max_blocks) goto end;
-								}
-							}
+		else
+		{
+			// Trying to re-order blocks
+			// Look for identical block in memory blocks
+			while (i < n-1)
+			{
+				// skip all zeroes blocks
+				if (memcmp(tmp_blocks[i], "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", 16))
+				{
+					for (j = 1; j < max_blocks - 1; ++j)
+					{
+						if (!memcmp(tmp_blocks[i], memory_blocks[j], 16) && !memory_blocks[j+1][ALLOC])
+						{
+							memcpy(memory_blocks[j+1], tmp_blocks[i+1], 16);
+							memory_blocks[j+1][ALLOC] = 1;
+							if (++found_blocks >= max_blocks) goto end;
 						}
 					}
 				}
+				if (memcmp(tmp_blocks[i+1], "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", 16))
+				{
+					for (j = 0; j < max_blocks; ++j)
+					{
+						if (!memcmp(tmp_blocks[i+1], memory_blocks[j], 16) && !memory_blocks[(j == 0 ? max_blocks : j) -1][ALLOC])
+						{
+							if (j == 0)
+							{
+								memcpy(memory_blocks[max_blocks - 1], tmp_blocks[i], 16);
+								memory_blocks[max_blocks - 1][ALLOC] = 1;
+							}
+							else
+							{
+								memcpy(memory_blocks[j-1], tmp_blocks[i], 16);
+								memory_blocks[j-1][ALLOC] = 1;
+							}
+							if (++found_blocks >= max_blocks) goto end;
+						}
+					}
+				}
+				++i;
 			}
 		}
-		tries++;
-		if (BUTTON_PRESS()) return;
-	} while (num_blocks != max_blocks);
+		++tries;
+		if (BUTTON_PRESS())
+		{
+			Dbprintf("Button pressed, stopping.");
+			goto end;
+		}
+	}
+	while (found_blocks != max_blocks);
+
  end:
 	Dbprintf("-----------------------------------------");
 	Dbprintf("Memory content:");
 	Dbprintf("-----------------------------------------");
-	for(i=0; i<max_blocks; i++) {
-		if(Blocks[i][ALLOC]==1)
-			Dbprintf("%02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x",
-					 Blocks[i][0], Blocks[i][1], Blocks[i][2], Blocks[i][3], Blocks[i][4], Blocks[i][5], Blocks[i][6], Blocks[i][7],
-					Blocks[i][8], Blocks[i][9], Blocks[i][10], Blocks[i][11], Blocks[i][12], Blocks[i][13], Blocks[i][14], Blocks[i][15]);
+	for (i = 0; i < max_blocks; ++i) {
+		if (memory_blocks[i][ALLOC])
+			print_block(memory_blocks[i]);
 		else
 			Dbprintf("<missing block %d>", i);
 	}
 	Dbprintf("-----------------------------------------");
-
+	
+	if (found_blocks < max_blocks)
+	{
+		Dbprintf("-----------------------------------------");
+		Dbprintf("Blocks with unknown position:");
+		Dbprintf("-----------------------------------------");
+		for (i = 0; i < single_blocks_cnt; ++i)
+			print_block(single_blocks[i]);
+		
+		Dbprintf("-----------------------------------------");
+	}
 	cmd_send(CMD_ACK,0,0,0,0,0);
 }
 
+static void RealWritePCF7931(uint8_t *pass, uint16_t init_delay, int32_t l, int32_t p, uint8_t address, uint8_t byte, uint8_t data)
+{
+	uint32_t tab[1024]={0}; // data times frame
+	uint32_t u = 0;
+	uint8_t parity = 0;
+	bool comp = 0;
+
+	//BUILD OF THE DATA FRAME
+	//alimentation of the tag (time for initializing)
+	AddPatternPCF7931(init_delay, 0, 8192/2*T0_PCF, tab);
+	AddPatternPCF7931(8192/2*T0_PCF + 319*T0_PCF+70, 3*T0_PCF, 29*T0_PCF, tab);
+	//password indication bit
+	AddBitPCF7931(1, tab, l, p);
+	// password (on 56 bits)
+	AddBytePCF7931(pass[0], tab, l, p);
+	AddBytePCF7931(pass[1], tab, l, p);
+	AddBytePCF7931(pass[2], tab, l, p);
+	AddBytePCF7931(pass[3], tab, l, p);
+	AddBytePCF7931(pass[4], tab, l, p);
+	AddBytePCF7931(pass[5], tab, l, p);
+	AddBytePCF7931(pass[6], tab, l, p);
+	//programming mode (0 or 1)
+	AddBitPCF7931(0, tab, l, p);
+	
+	//block adress on 6 bits
+	for (u = 0; u < 6; ++u)
+	{
+		if (address & (1 << u)) {	// bit 1
+			 ++parity;
+			 AddBitPCF7931(1, tab, l, p);
+		} else {					// bit 0
+			 AddBitPCF7931(0, tab, l, p);
+		}
+	}
+	
+	//byte address on 4 bits
+	for (u = 0; u < 4; ++u)
+	{
+		if (byte & (1 << u))
+		{	// bit 1
+			 parity++;
+			 AddBitPCF7931(1, tab, l, p);
+		}
+		else				// bit 0
+			 AddBitPCF7931(0, tab, l, p);
+	}
+	
+	//data on 8 bits
+	for (u=0; u<8; u++)
+	{
+		if (data&(1<<u)) {	// bit 1
+			 parity++;
+			 AddBitPCF7931(1, tab, l, p);
+		} 
+		else				//bit 0
+			 AddBitPCF7931(0, tab, l, p);
+	}
+
+	//parity bit
+	if ((parity % 2) == 0)
+	 	AddBitPCF7931(0, tab, l, p); //even parity
+	else
+		AddBitPCF7931(1, tab, l, p);//odd parity
+
+	//time access memory
+	AddPatternPCF7931(5120+2680, 0, 0, tab);
+
+	//conversion of the scale time
+	for (u = 0; u < 500; ++u)
+		tab[u] = (tab[u] * 3) / 2;
+
+	//compennsation of the counter reload
+	while (!comp)
+	{
+		comp = 1;
+		for (u = 0; tab[u] != 0; ++u)
+			if(tab[u] > 0xFFFF)
+			{
+			  tab[u] -= 0xFFFF;
+			  comp = 0;
+			}
+	}
+
+	SendCmdPCF7931(tab);
+}
+
+void BruteForcePCF7931(uint64_t password, uint8_t tries, uint16_t init_delay, int32_t l, int32_t p)
+{
+	uint8_t i = 0;
+	uint8_t pass_array[7];
+	
+	while (password < 0x00FFFFFFFFFFFFFF)
+	{
+		if (BUTTON_PRESS())
+		{
+			Dbprintf("Button pressed, stopping bruteforce ...");
+			return;
+		}
+		
+		pass_array[0] = password & 0xFF;
+		pass_array[1] = (password >> 8) & 0xFF;
+		pass_array[2] = (password >> 16) & 0xFF;
+		pass_array[3] = (password >> 24) & 0xFF;
+		pass_array[4] = (password >> 32) & 0xFF;
+		pass_array[5] = (password >> 48) & 0xFF;
+		pass_array[6] = (password >> 56) & 0xFF;
+
+		Dbprintf("Trying: %02x %02x %02x %02x %02x %02x %02x ...",
+			pass_array[0],
+			pass_array[1],
+			pass_array[2],
+			pass_array[3],
+			pass_array[4],
+			pass_array[5],
+			pass_array[6]);
+		
+		for (i = 0; i < tries; ++i)
+			RealWritePCF7931
+			(
+				pass_array,
+				init_delay,
+				l,
+				p,
+				0,
+				7,
+				0x01
+			);
+	
+		++password;	
+	}
+}
 
 /* Write on a byte of a PCF7931 tag
  * @param address : address of the block to write
@@ -279,105 +486,16 @@ void ReadPCF7931() {
  */
 void WritePCF7931(uint8_t pass1, uint8_t pass2, uint8_t pass3, uint8_t pass4, uint8_t pass5, uint8_t pass6, uint8_t pass7, uint16_t init_delay, int32_t l, int32_t p, uint8_t address, uint8_t byte, uint8_t data)
 {
-
-	uint32_t tab[1024]={0}; // data times frame
-	uint32_t u = 0;
-	uint8_t parity = 0;
-	bool comp = 0;
-
-	//BUILD OF THE DATA FRAME
-
-	//alimentation of the tag (time for initializing)
-	AddPatternPCF7931(init_delay, 0, 8192/2*T0_PCF, tab);
-
-	//PMC
 	Dbprintf("Initialization delay : %d us", init_delay);
-	AddPatternPCF7931(8192/2*T0_PCF + 319*T0_PCF+70, 3*T0_PCF, 29*T0_PCF, tab);
-
 	Dbprintf("Offsets : %d us on the low pulses width, %d us on the low pulses positions", l, p);
-
-	//password indication bit
-	AddBitPCF7931(1, tab, l, p);
-
-
-	//password (on 56 bits)
-	Dbprintf("Password (LSB first on each byte) : %02x %02x %02x %02x %02x %02x %02x", pass1,pass2,pass3,pass4,pass5,pass6,pass7);
-	AddBytePCF7931(pass1, tab, l, p);
-	AddBytePCF7931(pass2, tab, l, p);
-	AddBytePCF7931(pass3, tab, l, p);
-	AddBytePCF7931(pass4, tab, l, p);
-	AddBytePCF7931(pass5, tab, l, p);
-	AddBytePCF7931(pass6, tab, l, p);
-	AddBytePCF7931(pass7, tab, l, p);
-
-	//programming mode (0 or 1)
-	AddBitPCF7931(0, tab, l, p);
-
-	//block adress on 6 bits
+	Dbprintf("Password (LSB first on each byte): %02x %02x %02x %02x %02x %02x %02x", pass1, pass2, pass3, pass4, pass5, pass6, pass7);
 	Dbprintf("Block address : %02x", address);
-	for (u=0; u<6; u++)
-	{
-		if (address&(1<<u)) {	// bit 1
-			 parity++;
-			 AddBitPCF7931(1, tab, l, p);
-		} else{					// bit 0
-			 AddBitPCF7931(0, tab, l, p);
-		}
-	}
-
-	//byte address on 4 bits
 	Dbprintf("Byte address : %02x", byte);
-	for (u=0; u<4; u++)
-	{
-		if (byte&(1<<u)) {	// bit 1
-			 parity++;
-			 AddBitPCF7931(1, tab, l, p);
-		} else{				// bit 0
-			 AddBitPCF7931(0, tab, l, p);
-		}
-	}
-
-	//data on 8 bits
 	Dbprintf("Data : %02x", data);
-	for (u=0; u<8; u++)
-	{
-		if (data&(1<<u)) {	// bit 1
-			 parity++;
-			 AddBitPCF7931(1, tab, l, p);
-		} else{				//bit 0
-			 AddBitPCF7931(0, tab, l, p);
-		}
-	}
-
-
-	//parity bit
-	if((parity%2)==0){
-	 	AddBitPCF7931(0, tab, l, p); //even parity
-	}else{
-		AddBitPCF7931(1, tab, l, p);//odd parity
-	}
-
-	//time access memory
-	AddPatternPCF7931(5120+2680, 0, 0, tab);
-
-	//conversion of the scale time
-	for(u=0;u<500;u++){
-		tab[u]=(tab[u] * 3)/2;
-	}
-
-
-	//compennsation of the counter reload
-	while (!comp){
-		comp = 1;
-		for(u=0;tab[u]!=0;u++){
-			if(tab[u] > 0xFFFF){
-			  tab[u] -= 0xFFFF;
-			  comp = 0;
-			}
-		}
-	}
-
-	SendCmdPCF7931(tab);
+	
+	uint8_t password[7] = {pass1, pass2, pass3, pass4, pass5, pass6, pass7};
+	
+	RealWritePCF7931 (password, init_delay, l, p, address, byte, data);
 }
 
 
@@ -390,12 +508,10 @@ void SendCmdPCF7931(uint32_t * tab){
 	uint16_t u=0;
 	uint16_t tempo=0;
 
-	Dbprintf("SENDING DATA FRAME...");
+	Dbprintf("Sending data frame ...");
 
 	FpgaDownloadAndGo(FPGA_BITSTREAM_LF);
-
 	FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz
-
 	FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_PASSTHRU );
 
 	LED_A_ON();
@@ -412,41 +528,31 @@ void SendCmdPCF7931(uint32_t * tab){
 	AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKEN;
 	AT91C_BASE_TCB->TCB_BCR = 1;
 
-
 	tempo = AT91C_BASE_TC0->TC_CV;
-	for(u=0;tab[u]!= 0;u+=3){
-
-
+	for (u = 0; tab[u] !=  0; u += 3)
+	{
 		// modulate antenna
 		HIGH(GPIO_SSC_DOUT);
-		while(tempo !=  tab[u]){
+		while(tempo !=  tab[u])
 			tempo = AT91C_BASE_TC0->TC_CV;
-		}
-
+			
 		// stop modulating antenna
 		LOW(GPIO_SSC_DOUT);
-		while(tempo !=  tab[u+1]){
+		while(tempo !=  tab[u+1])
 			tempo = AT91C_BASE_TC0->TC_CV;
-		}
-
 
 		// modulate antenna
 		HIGH(GPIO_SSC_DOUT);
-		while(tempo !=  tab[u+2]){
+		while(tempo !=  tab[u+2])
 			tempo = AT91C_BASE_TC0->TC_CV;
-		}
-
-
 	}
 
 	LED_A_OFF();
 	FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
 	SpinDelay(200);
 
-
 	AT91C_BASE_TC0->TC_CCR = AT91C_TC_CLKDIS; // timer disable
-	DbpString("FINISH !");
-	DbpString("(Could be usefull to send the same trame many times)");
+	DbpString("Data frame sent (multiple sends may be needed)");
 	LED(0xFFFF, 1000);
 }
 
@@ -482,8 +588,7 @@ bool AddBytePCF7931(uint8_t byte, uint32_t * tab, int32_t l, int32_t p){
 bool AddBitPCF7931(bool b, uint32_t * tab, int32_t l, int32_t p){
 	uint8_t u = 0;
 
-	for(u=0;tab[u]!=0;u+=3){} //we put the cursor at the last value of the array
-	
+	for (u = 0; tab[u] != 0; u += 3){} //we put the cursor at the last value of the array
 
 	if(b==1){	//add a bit 1
 		if(u==0) tab[u] = 34*T0_PCF+p;
diff --git a/armsrc/pcf7931.h b/armsrc/pcf7931.h
index 26aaff68..662017aa 100644
--- a/armsrc/pcf7931.h
+++ b/armsrc/pcf7931.h
@@ -1,14 +1,15 @@
 #ifndef __PCF7931_H
 #define __PCF7931_H
 
-int DemodPCF7931(uint8_t **outBlocks);
-int IsBlock0PCF7931(uint8_t *Block);
-int IsBlock1PCF7931(uint8_t *Block);
+size_t DemodPCF7931(uint8_t **outBlocks);
+uint8_t IsBlock0PCF7931(uint8_t *Block);
+uint8_t IsBlock1PCF7931(uint8_t *Block);
 void ReadPCF7931();
 void SendCmdPCF7931(uint32_t * tab);
 bool AddBytePCF7931(uint8_t byte, uint32_t * tab, int32_t l, int32_t p);
 bool AddBitPCF7931(bool b, uint32_t * tab, int32_t l, int32_t p);
 bool AddPatternPCF7931(uint32_t a, uint32_t b, uint32_t c, uint32_t * tab);
 void WritePCF7931(uint8_t pass1, uint8_t pass2, uint8_t pass3, uint8_t pass4, uint8_t pass5, uint8_t pass6, uint8_t pass7, uint16_t init_delay, int32_t l, int32_t p, uint8_t address, uint8_t byte, uint8_t data);
+void BruteForcePCF7931(uint64_t start_password, uint8_t tries, uint16_t init_delay, int32_t l, int32_t p);
 
 #endif
diff --git a/client/cmdlfpcf7931.c b/client/cmdlfpcf7931.c
index 9c694b8d..559f6d18 100644
--- a/client/cmdlfpcf7931.c
+++ b/client/cmdlfpcf7931.c
@@ -1,6 +1,7 @@
 //-----------------------------------------------------------------------------
 // Copyright (C) 2012 Chalk <chalk.secu at gmail.com>
 //               2015 Dake <thomas.cayrou at gmail.com>
+//				 2018 sguerrini97 <sguerrini97 at gmail.com>
 
 // This code is licensed to you under the terms of the GNU GPL, version 2 or,
 // at your option, any later version. See the LICENSE.txt file for the text of
@@ -76,6 +77,19 @@ int usage_pcf7931_write(){
 	return 0;
 }
 
+int usage_pcf7931_bruteforce()
+{
+	PrintAndLog("Usage: lf pcf7931 bruteforce [h] <start password> <tries>");
+	PrintAndLog("This command tries to write a PCF7931 tag.");
+	PrintAndLog("Options:");
+	PrintAndLog("       h          This help");
+	PrintAndLog("       start password   hex password to start from");
+	PrintAndLog("       tries    How many times to send the same data frame");
+	PrintAndLog("Examples:");
+	PrintAndLog("      lf pcf7931 bruteforce 00000000123456 3");
+	return 0;
+}
+
 int usage_pcf7931_config(){
 	PrintAndLog("Usage: lf pcf7931 config [h] [r] <pwd> <delay> <offset width> <offset position>");
 	PrintAndLog("This command tries to set the configuration used with PCF7931 commands");
@@ -159,12 +173,47 @@ int CmdLFPCF7931Write(const char *Cmd){
 	return 0;
 }
 
+int CmdLFPCF7931BruteForce(const char *Cmd){
+
+	uint8_t ctmp = param_getchar(Cmd, 0);
+	if (strlen(Cmd) < 1 || ctmp == 'h' || ctmp == 'H') return usage_pcf7931_bruteforce();  
+
+	uint64_t start_password = 0;
+	uint8_t tries = 3;
+	
+	if (param_gethex(Cmd, 0, (uint8_t*)(&start_password), 14)) return usage_pcf7931_bruteforce();
+	if (param_getdec(Cmd, 1, &tries)) return usage_pcf7931_bruteforce();
+	
+	PrintAndLog("Bruteforcing from password: %02x %02x %02x %02x %02x %02x %02x",
+			start_password & 0xFF,
+			(start_password >> 8) & 0xFF,
+			(start_password >> 16) & 0xFF,
+			(start_password >> 24) & 0xFF,
+			(start_password >> 32) & 0xFF,
+			(start_password >> 48) & 0xFF,
+			(start_password >> 56) & 0xFF);
+			
+	PrintAndLog("Trying each password %d times", tries);
+
+	UsbCommand c = {CMD_PCF7931_BRUTEFORCE, {start_password, tries} };
+	
+	c.d.asDwords[7] = (configPcf.OffsetWidth + 128);
+	c.d.asDwords[8] = (configPcf.OffsetPosition + 128);
+	c.d.asDwords[9] = configPcf.InitDelay;
+
+	clearCommandBuffer();
+	SendCommand(&c);
+	//no ack?
+	return 0;
+}
+
 static command_t CommandTable[] = 
 {
 	{"help",   CmdHelp,            1, "This help"},
 	{"read",   CmdLFPCF7931Read,   0, "Read content of a PCF7931 transponder"},
 	{"write",  CmdLFPCF7931Write,  0, "Write data on a PCF7931 transponder."},
 	{"config", CmdLFPCF7931Config, 1, "Configure the password, the tags initialization delay and time offsets (optional)"},
+	{"bruteforce", CmdLFPCF7931BruteForce, 0, "Bruteforce a PCF7931 transponder password."},
 	{NULL,     NULL,               0, NULL}
 };
 
diff --git a/client/cmdlfpcf7931.h b/client/cmdlfpcf7931.h
index 8b24f03a..32f8491e 100644
--- a/client/cmdlfpcf7931.h
+++ b/client/cmdlfpcf7931.h
@@ -1,6 +1,7 @@
 //-----------------------------------------------------------------------------
 // Copyright (C) 2012 Chalk <chalk.secu at gmail.com>
 //				 2015 Dake <thomas.cayrou at gmail.com>
+//				 2018 sguerrini97 <sguerrini97 at gmail.com>
 
 // This code is licensed to you under the terms of the GNU GPL, version 2 or,
 // at your option, any later version. See the LICENSE.txt file for the text of
@@ -26,12 +27,14 @@ int pcf7931_printConfig();
 
 int usage_pcf7931_read();
 int usage_pcf7931_write();
+int usage_pcf7931_bruteforce();
 int usage_pcf7931_config();
 
 int CmdLFPCF7931(const char *Cmd);
 
 int CmdLFPCF7931Read(const char *Cmd);
 int CmdLFPCF7931Write(const char *Cmd);
+int CmdLFPCF7931BruteForce(const char *Cmd);
 int CmdLFPCF7931Config(const char *Cmd);
 
 #endif
diff --git a/include/usb_cmd.h b/include/usb_cmd.h
index fa66634f..f744a03f 100644
--- a/include/usb_cmd.h
+++ b/include/usb_cmd.h
@@ -97,6 +97,7 @@ typedef struct{
 #define CMD_T55XX_RESET_READ                                              0x0216
 #define CMD_PCF7931_READ                                                  0x0217
 #define CMD_PCF7931_WRITE                                                 0x0222
+#define CMD_PCF7931_BRUTEFORCE											  0x0226
 #define CMD_EM4X_READ_WORD                                                0x0218
 #define CMD_EM4X_WRITE_WORD                                               0x0219
 #define CMD_IO_DEMOD_FSK                                                  0x021A