Command Flow

Keywords
--------

  - The system is only able to process one command at a time (both SYS and DIR commands).
  - ComInstance.ReplyStatus holds the information about command processing.
  - Writing flag indicated that the reply is ready to be transmitted
  - Direct commands are commands to be interpreted by VM - Direct commands are not interpreted until process is
    returned to the VM
  - System commands are usually processed when received except for large messages (messages larger that buffersize)
  - Brick responds on the same channel as a message is received - ComInstance.ActiveComCh = received channel

  Message flow
  ------------

  Direct command --------------> When received  ---->  if reply required     ---->  ComInstance.ReplyStatus = DIR_CMD_REPLY
                                       |
                                       '------------>  if no reply required  ---->  ComInstance.ReplyStatus = DIR_CMD_NOREPLY

  VM reply to direct command  -> if (ComInstance.ReplyStatus = DIR_CMD_REPLY)---->  pTxBuf->Writing         = 1
  (VM always replies, after interpretation)                                         ComInstance.ReplyStatus = 0
             |
             '-----------------> if (ComInstance.ReplyStatus = DIR_CMD_NOREPLY)-->  pTxBuf->Writing         = 0
                                                                                    ComInstance.ReplyStatus = 0


  System command --------------> if reply required ->  ComInstance.ReplyStatus = SYS_CMD_REPLY  --> if (pRxBuf->State  =  RXFILEDL) -> Do nothing
       |                                                                 |
       |                                                                 '------------------------> if (pRxBuf->State  != RXFILEDL) -> pTxBuf->Writing         = 1
       |                                                                                                                               ComInstance.ReplyStatus = 0
       |
       '-----------------------> If reply not req. ->  ComInstance.ReplyStatus = SYS_CMD_NOREPLY -> if (pRxBuf->State  =  RXFILEDL) -> Do nothing
                                                                         |
                                                                         '------------------------> if (pRxBuf->State  != RXFILEDL) -> ComInstance.ReplyStatus = 0


  Large messages - Massages larger than buffer size (1024 bytes):

    Potential large message commands:
    - BEGIN_DOWNLOAD
    - CONTINUE_DOWNLOAD
    - BEGIN_UPLOAD
    - CONTINUE_UPLOAD
    - BEGIN_GETFILE
    - CONTINUE_GETFILE
    - LIST_FILES
    - CONTINUE_LIST_FILES


  Large files --------->   (Message size <= Buffer size)  -->  Write bytes to file
       |                                                  -->  pRxBuf->State  =  RXIDLE
       |
       |
       '--------------->   (Message size  > Buffer Size)  -->  Write bytes from buffer
                                                          -->  pRxBuf->State  =  RXFILEDL

        Buffer full --->   if pRxBuf->State  =  RXFILEDL  -->  Yes -> write into buffer
                                         |                                   |
                                         |                                   '------------------> if Remainig msg = 0 -->  pRxBuf->State  =  RXIDLE
                                         |
                                         '------------------>  No --> Interprete as new command