Index: firmware/App/Services/CommBuffers.c
===================================================================
diff -u -r0c085209bea23f66011059a7c19796c1e4b246fa -rfc9a9244cf4288ff0623c3e02455ac565bf60cdd
--- firmware/App/Services/CommBuffers.c	(.../CommBuffers.c)	(revision 0c085209bea23f66011059a7c19796c1e4b246fa)
+++ firmware/App/Services/CommBuffers.c	(.../CommBuffers.c)	(revision fc9a9244cf4288ff0623c3e02455ac565bf60cdd)
@@ -11,11 +11,12 @@
 
 // ********** private definitions **********
 
-#define UPDATE_PACKET_SIZE_BYTES ( SW_UPDATE_FLASH_BUFFER_SIZE + CAN_MESSAGE_PAYLOAD_SIZE )    ///< Software update packet size in bytes.
+#define UPDATE_PACKET_SIZE_BYTES ( SW_UPDATE_FLASH_BUFFER_SIZE + CAN_MESSAGE_FRAME_SIZE )      ///< Software update packet size in bytes.
 
 /// Software update buffer structure
 typedef struct
 {
+    U32 SWUpdateNumOfFramesCount;                                                              ///< Software update number of frame count.
     U32 SWUpdateFrameCount;                                                                    ///< Software update frame count.
     U08 SWUpdateBuffer[ UPDATE_PACKET_SIZE_BYTES ];                                            ///< Software update buffer.
 } SW_UPDATE_BUFFER_T;
@@ -66,13 +67,42 @@
         U32 currentFrameCount = SWUpdateBuffer[ mailBox ].SWUpdateFrameCount;
 
         // Check if the number of bytes is less than the allowed bytes in the mailbox buffer.
-        if ( ( currentFrameCount * CAN_MESSAGE_PAYLOAD_SIZE ) <= UPDATE_PACKET_SIZE_BYTES )
+        if ( ( currentFrameCount * CAN_MESSAGE_FRAME_SIZE ) <= UPDATE_PACKET_SIZE_BYTES )
         {
             U32 currentBufferIndex = currentFrameCount * len;
 
             // Copy the received can frame into the buffer
             memcpy( SWUpdateBuffer[ mailBox ].SWUpdateBuffer + currentBufferIndex, data, len );
 
+            switch ( mailBox )
+            {
+                case SW_UPDATE_COMMAD:
+                    // A command is only 1 frame of 8 bytes.
+                    SWUpdateBuffer[ mailBox ].SWUpdateNumOfFramesCount = NUM_OF_CMD_CAN_FRAMES;
+                    break;
+
+                case SW_UPDATE_TD_UPDATE:
+                case SW_UPDATE_DD_UPDATE:
+                    if ( 0 == SWUpdateBuffer[ mailBox ].SWUpdateFrameCount )
+                    {
+                        // If the received command is a software update mailbox and if the frame count is 0, so it is the overhead frame.
+                        // In the overhead frame the 2nd and 3rd bytes are payload length and the two payloads are bitwised to get the payload length.
+                        U08 updatePayloadLenMSB = SWUpdateBuffer[ mailBox ].SWUpdateBuffer[ SW_UPDATE_LEN_MSB_INDEX ];
+                        U08 updatePayloadLenLSB = SWUpdateBuffer[ mailBox ].SWUpdateBuffer[ SW_UPDATE_LEN_LSB_INDEX ];
+                        U16 updatePayloadLength = updatePayloadLenMSB << SHIFT_8_BITS_FOR_BYTE_SHIFT | updatePayloadLenLSB;
+                        // Per the payload length, calculate the number of frames of 8 bytes that are needed to receive the entire update message.
+                        // Round up the number of frames with (payload length + 1 can frame (8 bytes) - 1) / 1 can frame (8 bytes)
+                        // After calculating the number of frames needed to receive the entire update payload add one more frame for the overhead frame.
+                        SWUpdateBuffer[ mailBox ].SWUpdateNumOfFramesCount  = ( updatePayloadLength + CAN_MESSAGE_FRAME_SIZE - 1 ) / CAN_MESSAGE_FRAME_SIZE;
+                        SWUpdateBuffer[ mailBox ].SWUpdateNumOfFramesCount += 1;
+                    }
+                    break;
+
+                default:
+                    // Do nothing. There are other mailboxes that do not need to be processed.
+                    break;
+            }
+
             // Increment the current frame count
             SWUpdateBuffer[ mailBox ].SWUpdateFrameCount += 1;
             status                                        = TRUE;
@@ -115,23 +145,44 @@
 
 /*********************************************************************//**
  * @brief
- * The getNumberOfBytesInBuffer function determines how many bytes
- * are currently contained in a given comm buffer.
+ * The isMessageComplete function checks whether a message (command or update)
+ * has been fully received.
  * @details Inputs: SWUpdateBuffer[]
  * @details Outputs: none
- * @param mailbox ID of buffer to get byte count for
- * @return the number of bytes currently in the given comm buffer.
+ * @param mailbox ID of buffer to check the completeness of the message
+ * @return TRUE if the messages has been fully received, otherwise FALSE
  *************************************************************************/
-S32 getNumberOfBytesInBuffer( SW_UPDATE_CAN_MAIL_BOX_T mailBox )
+BOOL isMessageComplete( SW_UPDATE_CAN_MAIL_BOX_T mailBox )
 {
-    S32 bytes = -1;
+    BOOL status        = FALSE;
+    U32 frameCnt       = 0;
+    U32 numOfFramesCnt = 0;
 
-    if ( mailBox < NUM_OF_SW_UPDATE_MBOXES )
+    switch ( mailBox )
     {
-        bytes = SWUpdateBuffer[ mailBox ].SWUpdateFrameCount * CAN_MESSAGE_PAYLOAD_SIZE;
+        case SW_UPDATE_COMMAD:
+            frameCnt       = SWUpdateBuffer[ mailBox ].SWUpdateFrameCount;
+            numOfFramesCnt = SWUpdateBuffer[ mailBox ].SWUpdateNumOfFramesCount;
+            break;
+
+        case SW_UPDATE_TD_UPDATE:
+        case SW_UPDATE_DD_UPDATE:
+            frameCnt       = SWUpdateBuffer[ mailBox ].SWUpdateFrameCount;
+            numOfFramesCnt = SWUpdateBuffer[ mailBox ].SWUpdateNumOfFramesCount;
+            break;
+
+        default:
+            // Do nothing. There are other mailboxes that do not need to be processed.
+            break;
     }
 
-    return bytes;
+    // Check if the frame count is not 0 meaning that at least one frame is received prior to checking for the completion.
+    if ( ( frameCnt > 0 ) && ( frameCnt == numOfFramesCnt ) )
+    {
+        status = TRUE;
+    }
+
+    return status;
 }
 
 /*********************************************************************//**