Fixed timing issues with Read Multiple Blocks

ISO15693 CRC calculation is slow and it delayed too much transmission of long frames. Some readers marked transmission as unsuccesfull and ignored data. Moving CRC calculation inside the codec allows to start modulating the field while the CRC is not yet ready but, by the time it has to be trasmitted, calculation will be done. This fixes emsec#262 In EM4233, there still are issues with Read Multiple command when block locking status is requested for more than 0x1F blocks Implemented a check in ISO15693 codec to avoid out of bound CRC writes.
RfidResearchGroup · Sep 10, 2020 · ebd6ab5 · ebd6ab5
1 parent d439424
commit ebd6ab5
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Showing 5 changed files with 14 additions and 27 deletions.
diff --git a/Firmware/Chameleon-Mini/Application/EM4233.c b/Firmware/Chameleon-Mini/Application/EM4233.c
@@ -137,7 +137,7 @@ uint16_t EM4233_Read_Single(uint8_t *FrameBuf, uint16_t FrameBytes) {
     if (BlockAddress >= EM4233_NUMBER_OF_BLCKS) { /* check if the reader is requesting a sector out of bound */
         if (FrameInfo.Addressed) { /* If the request is addressed */
             FrameBuf[ISO15693_ADDR_FLAGS] = ISO15693_RES_FLAG_ERROR;
-            FrameBuf[ISO15693_RES_ADDR_PARAM] = 0x0F; /* Magic number from real tag */
+            FrameBuf[ISO15693_RES_ADDR_PARAM] = ISO15693_RES_ERR_GENERIC;
             ResponseByteCount += 2; /* Copied this behaviour from real tag, not specified in ISO documents */
         }
         return ResponseByteCount; /* If not addressed real tag does not respond */
@@ -178,7 +178,7 @@ uint16_t EM4233_Read_Multiple(uint8_t *FrameBuf, uint16_t FrameBytes) {
     if (BlockAddress >= EM4233_NUMBER_OF_BLCKS) { /* the reader is requesting a block out of bound */
         if (FrameInfo.Addressed) { /* If the request is addressed */
             FrameBuf[ISO15693_ADDR_FLAGS] = ISO15693_RES_FLAG_ERROR;
-            FrameBuf[ISO15693_RES_ADDR_PARAM] = 0x0F; /* Magic number from real tag */
+            FrameBuf[ISO15693_RES_ADDR_PARAM] = ISO15693_RES_ERR_GENERIC;
             ResponseByteCount += 2; /* Copied this behaviour from real tag, not specified in ISO documents */
         }
         return ResponseByteCount; /* If not addressed real tag does not respond */
@@ -669,12 +669,6 @@ uint16_t EM4233AppProcess(uint8_t *FrameBuf, uint16_t FrameBytes) {
         }
     }
 
-    if (ResponseByteCount > 0) {
-        /* There is data to send. Append CRC */
-        ISO15693AppendCRC(FrameBuf, ResponseByteCount);
-        ResponseByteCount += ISO15693_CRC16_SIZE;
-    }
-
     return ResponseByteCount;
 }
 

diff --git a/Firmware/Chameleon-Mini/Application/Sl2s2002.c b/Firmware/Chameleon-Mini/Application/Sl2s2002.c
@@ -141,12 +141,6 @@ uint16_t Sl2s2002AppProcess(uint8_t *FrameBuf, uint16_t FrameBytes) {
                     break;
             }
 
-            if (ResponseByteCount > 0) {
-                /* There is data to be sent. Append CRC */
-                ISO15693AppendCRC(FrameBuf, ResponseByteCount);
-                ResponseByteCount += ISO15693_CRC16_SIZE;
-            }
-
             return ResponseByteCount;
 
         } else { // Invalid CRC

diff --git a/Firmware/Chameleon-Mini/Application/TITagitstandard.c b/Firmware/Chameleon-Mini/Application/TITagitstandard.c
@@ -198,12 +198,6 @@ uint16_t TITagitstandardAppProcess(uint8_t *FrameBuf, uint16_t FrameBytes) {
             break;
     }
 
-    if (ResponseByteCount > 0) {
-        /* There is data to be sent. Append CRC */
-        ISO15693AppendCRC(FrameBuf, ResponseByteCount);
-        ResponseByteCount += ISO15693_CRC16_SIZE;
-    }
-
     return ResponseByteCount;
 }
 

diff --git a/Firmware/Chameleon-Mini/Application/Vicinity.c b/Firmware/Chameleon-Mini/Application/Vicinity.c
@@ -92,12 +92,6 @@ uint16_t VicinityAppProcess(uint8_t *FrameBuf, uint16_t FrameBytes) {
                     break;
             }
 
-            if (ResponseByteCount > 0) {
-                /* There is data to be sent. Append CRC */
-                ISO15693AppendCRC(FrameBuf, ResponseByteCount);
-                ResponseByteCount += ISO15693_CRC16_SIZE;
-            }
-
             return ResponseByteCount;
 
         } else { // Invalid CRC

diff --git a/Firmware/Chameleon-Mini/Codec/ISO15693.c b/Firmware/Chameleon-Mini/Codec/ISO15693.c
@@ -638,7 +638,13 @@ void ISO15693CodecTask(void) {
 
         /* This is only reached when we've received a valid frame */
         if (AppReceivedByteCount != ISO15693_APP_NO_RESPONSE) {
-            LogEntry(LOG_INFO_CODEC_TX_DATA, CodecBuffer, AppReceivedByteCount);
+            if (AppReceivedByteCount > CODEC_BUFFER_SIZE - ISO15693_CRC16_SIZE) { /* CRC would be written outside codec buffer */
+                CodecBuffer[ISO15693_ADDR_FLAGS] = ISO15693_RES_FLAG_ERROR;
+                CodecBuffer[ISO15693_RES_ADDR_PARAM] = ISO15693_RES_ERR_NOT_SUPP;
+                AppReceivedByteCount = 2;
+                LogEntry(LOG_INFO_GENERIC, "Too much data requested - See PR #274", 38);
+            }
+
             LEDHook(LED_CODEC_TX, LED_PULSE);
 
             ByteCount = AppReceivedByteCount;
@@ -653,6 +659,11 @@ void ISO15693CodecTask(void) {
                 StateRegister = LOADMOD_START_SINGLE;
             }
 
+            /* Calculate the CRC while modulation is already ongoing */
+            ISO15693AppendCRC(CodecBuffer, AppReceivedByteCount);
+            ByteCount += ISO15693_CRC16_SIZE; /* Increase this variable as it will be read by the codec during loadmodulation */
+            LogEntry(LOG_INFO_CODEC_TX_DATA, CodecBuffer, AppReceivedByteCount + ISO15693_CRC16_SIZE);
+
         } else {
             /* Overwrite the PERBUF register, which was configured in ISO15693_EOC, with the new appropriate value.
              * This is expecially needed because, since load modulation has not been performed, we're jumping here straight after