First draft of anticollision sequence

Only 1 slot mode has been implemented, but it seems to work even for 16 slots mode. This needs to be checked with other readers.

Firmware/Chameleon-Mini/Application/EM4233.c

@@ -15,6 +15,7 @@ static enum {
 } State;
 
 bool loggedIn;
+uint8_t MyAFI; /* This variable holds current tag's AFI (is used in inventory) */
 
 CurrentFrame FrameInfo;
 
@@ -29,6 +30,7 @@ void EM4233AppInit(void)
     FrameInfo.Addressed     = false;
     FrameInfo.Selected      = false;
     loggedIn = false;
+    MemoryReadBlock(&MyAFI, EM4233_MEM_AFI_ADDRESS, 1);
 
 }
 
@@ -238,6 +240,7 @@ uint16_t EM4233_Write_AFI(uint8_t* FrameBuf, uint16_t FrameBytes)
     }
 
     MemoryWriteBlock(&AFI, EM4233_MEM_AFI_ADDRESS, 1); /* Actually write new AFI */
+    MyAFI = AFI; /* And update global variable */
 
     // FrameBuf[ISO15693_ADDR_FLAGS] = ISO15693_RES_FLAG_NO_ERROR; /* flags */
     // ResponseByteCount += 1;
@@ -493,15 +496,20 @@ uint16_t EM4233AppProcess(uint8_t* FrameBuf, uint16_t FrameBytes)
     uint8_t Uid[ActiveConfiguration.UidSize];
     EM4233GetUid(Uid);
 
-    if (!ISO15693PrepareFrame(FrameBuf, FrameBytes, &FrameInfo, Uid))
+    if (!ISO15693PrepareFrame(FrameBuf, FrameBytes, &FrameInfo, Uid, MyAFI))
         return ISO15693_APP_NO_RESPONSE;
 
     if (State == STATE_READY || State == STATE_SELECTED) {
         if (*FrameInfo.Command == ISO15693_CMD_INVENTORY) {
-            FrameBuf[ISO15693_ADDR_FLAGS] = ISO15693_RES_FLAG_NO_ERROR;
-            MemoryReadBlock(&FrameBuf[ISO15693_RES_ADDR_PARAM], EM4233_MEM_DSFID_ADDRESS, 1);
-            ISO15693CopyUid(&FrameBuf[ISO15693_RES_ADDR_PARAM + 0x01], Uid);
-            ResponseByteCount = 10;
+            if (FrameInfo.ParamLen == 0)
+                return ISO15693_APP_NO_RESPONSE; /* malformed: not enough or too much data */
+
+            if (ISO15693AntiColl (FrameBuf, FrameBytes, &FrameInfo, Uid)) {
+                FrameBuf[ISO15693_ADDR_FLAGS] = ISO15693_RES_FLAG_NO_ERROR;
+                MemoryReadBlock(&FrameBuf[ISO15693_RES_ADDR_PARAM], EM4233_MEM_DSFID_ADDRESS, 1);
+                ISO15693CopyUid(&FrameBuf[ISO15693_RES_ADDR_PARAM + 0x01], Uid);
+                ResponseByteCount += 10;
+            }
 
         } else if ( (*FrameInfo.Command == ISO15693_CMD_STAY_QUIET ) && FrameInfo.Addressed) {
             State = STATE_QUIET;

Firmware/Chameleon-Mini/Application/ISO15693-A.c

@@ -65,7 +65,7 @@ bool ISO15693CheckCRC(void* FrameBuf, uint16_t FrameBufSize)
  * 
  * Authors: ceres-c & MrMoDDoM
  */
-bool ISO15693PrepareFrame(uint8_t* FrameBuf, uint16_t FrameBytes, CurrentFrame* FrameStruct, uint8_t* MyUid)
+bool ISO15693PrepareFrame(uint8_t* FrameBuf, uint16_t FrameBytes, CurrentFrame* FrameStruct, uint8_t* MyUid, uint8_t MyAFI)
 {
     if ((FrameBytes < ISO15693_MIN_FRAME_SIZE) || !ISO15693CheckCRC(FrameBuf, FrameBytes - ISO15693_CRC16_SIZE))
         /* malformed frame */
@@ -91,10 +91,18 @@ bool ISO15693PrepareFrame(uint8_t* FrameBuf, uint16_t FrameBytes, CurrentFrame*
 
     if ( (*FrameStruct -> Command) >= 0xA0) { /* if command is Custom or  Proprietary */
         /* then between CMD and UID is placed another byte which is IC Mfg Code, but we don't need it */
-        FrameStruct -> Parameters += 0x01;
         if (FrameBuf[ISO15693_REQ_ADDR_PARAM] != MyUid[1])
             /* if IC Mfg Code is different from our Mfg code (2nd byte of UID), then don't respond */
             return false;
+        FrameStruct -> Parameters += 0x01;
+    }
+    else if ( ((*FrameStruct -> Command) == ISO15693_CMD_INVENTORY) && (FrameBuf[ISO15693_ADDR_FLAGS] & ISO15693_REQ_FLAG_AFI)) {
+    /* or if it is Inventory with AFI flag set */
+        /* then between CMD and UID is placed another byte which is requested AFI, but we don't need it */
+        if (FrameBuf[ISO15693_REQ_ADDR_PARAM] != MyAFI)
+            /* if requested AFI is different from our current one, then don't respond */
+            return false;
+        FrameStruct -> Parameters += 0x01;
     }
 
     FrameStruct -> ParamLen = FrameBuf + (FrameBytes - ISO15693_CRC16_SIZE) - (FrameStruct -> Parameters);
@@ -108,3 +116,49 @@ bool ISO15693PrepareFrame(uint8_t* FrameBuf, uint16_t FrameBytes, CurrentFrame*
         return true;
     }
 }
+
+/*
+ * ISO15693AntiColl
+ *
+ * This function performs ISO15693 Anticollision
+ *
+ * Returns:
+ *  - true:  Inventory is addressed to us and a response is needed
+ *  - false: Request is not addressed to us (different bitmask)
+ *           and no response should be issued.
+ *
+ * Authors: ceres-c
+ *
+ * TODO:
+ *  - Implement 16 slots mode (still, it seems to work as it is, even for 16 slots mode ._.)
+ */
+bool ISO15693AntiColl(uint8_t* FrameBuf, uint16_t FrameBytes, CurrentFrame* FrameStruct, uint8_t* MyUid) {
+    uint8_t CurrentUID[ ISO15693_GENERIC_UID_SIZE ]; /* Holds the UID flipped */
+    ISO15693CopyUid(CurrentUID, MyUid);
+
+    uint8_t MaskLenght = *FrameStruct -> Parameters; /* First byte of parameters is mask lenght... */
+    uint8_t* MaskValue = FrameStruct -> Parameters + 1; /* ... then the mask itself begins */
+    uint8_t BytesNum = MaskLenght / 8; /* Gets the number of full bytes in mask */
+    uint8_t BitsNum = MaskLenght % 8; /* Gets the number of spare bits */
+
+    uint8_t B; /* B stands for Bytes and will be our reference point (I know, terrible name, I'm sorry) */
+    /* Compare the full bytes in mask with UID */
+    for (B = 0; B < BytesNum; B++ ) {
+        if (CurrentUID[B] != MaskValue[B])
+            return false; /* UID different */
+    }
+    /* Once we got here, B points for sure to the last byte of the mask, the one composed of spare bits */
+
+    /* Compare spare bits in mask with bits of UID */
+    uint8_t BitsMask = ((1 << BitsNum) - 1); /* (1 << Bits) = 00010000   ->   (1 << Bits) - 1 = 00001111 */
+    if ((MaskValue[B] & BitsMask) != (CurrentUID[B] & BitsMask)) {
+    /*  |-----------------------| Here we extract bits from the mask we received from the reader
+     *                               |------------------------| Here we extract bits from the UID
+     * The two extracted bit vectors are compared, if different then we're not the addressee.
+     * Only the latest byte of MaskValue and UID is considered.
+     */
+        return false;
+    }
+
+    return true;
+}

Firmware/Chameleon-Mini/Application/ISO15693-A.h

@@ -88,7 +88,8 @@ typedef struct {
 
 void ISO15693AppendCRC(uint8_t* FrameBuf, uint16_t FrameBufSize);
 bool ISO15693CheckCRC(void* FrameBuf, uint16_t FrameBufSize);
-bool ISO15693PrepareFrame(uint8_t* FrameBuf, uint16_t FrameBytes, CurrentFrame* FrameStruct, uint8_t* MyUid);
+bool ISO15693PrepareFrame(uint8_t* FrameBuf, uint16_t FrameBytes, CurrentFrame* FrameStruct, uint8_t* MyUid, uint8_t MyAFI);
+bool ISO15693AntiColl(uint8_t* FrameBuf, uint16_t FrameBytes, CurrentFrame* FrameStruct, uint8_t* MyUid);
 
 INLINE
 bool ISO15693CompareUid(uint8_t* Uid1, uint8_t* Uid2)

Firmware/Chameleon-Mini/Application/TITagitstandard.c

@@ -16,6 +16,7 @@ static enum {
     STATE_QUIET
 } State;
 
+uint8_t MyAFI;                      /* Holds current tag's AFI (is used in inventory) */
 uint16_t UserLockBits_Mask = 0;     /* Holds lock state of blocks */
 uint16_t FactoryLockBits_Mask = 0;  /* Holds lock state of blocks */
 CurrentFrame FrameInfo;
@@ -33,6 +34,8 @@ void TITagitstandardAppInit(void)
     FrameInfo.ParamLen      = 0;
     FrameInfo.Addressed     = false;
     FrameInfo.Selected      = false;
+
+    MemoryReadBlock(&MyAFI, TITAGIT_MEM_AFI_ADDRESS, 1);
 }
 
 void TITagitstandardAppReset(void)
@@ -64,7 +67,7 @@ uint16_t TITagitstandardAppProcess(uint8_t* FrameBuf, uint16_t FrameBytes)
     uint8_t Uid[ActiveConfiguration.UidSize];
     TITagitstandardGetUid(Uid);
 
-    if (!ISO15693PrepareFrame(FrameBuf, FrameBytes, &FrameInfo, Uid))
+    if (!ISO15693PrepareFrame(FrameBuf, FrameBytes, &FrameInfo, Uid, MyAFI))
         return ISO15693_APP_NO_RESPONSE;
 
     switch(State) {

Firmware/Chameleon-Mini/Application/TITagitstandard.h

@@ -12,10 +12,11 @@
 #include "Application.h"
 
 #define TITAGIT_STD_UID_SIZE        ISO15693_GENERIC_UID_SIZE  //ISO15693_UID_SIZE
-#define TITAGIT_STD_MEM_SIZE        44 //TAG-IT STANDARD MAX MEM SIZE
+#define TITAGIT_STD_MEM_SIZE        44          //TAG-IT STANDARD MAX MEM SIZE
 #define TITAGIT_BYTES_PER_PAGE      4
 #define TITAGIT_NUMBER_OF_SECTORS   ( TITAGIT_STD_MEM_SIZE / TITAGIT_BYTES_PER_PAGE )
 #define TITAGIT_MEM_UID_ADDRESS     0x20
+#define TITAGIT_MEM_AFI_ADDRESS     0x28        // AFI byte address
 
 void TITagitstandardAppInit(void);
 void TITagitstandardAppReset(void);