Changed the MSTP_MASTER_STATE_ANSWER_DATA_REQUEST state to always send a REPLY_POSTPONED by

commenting out the section that checks for new packets to send.  It was not the intent of the BACnet standard, but it makes the Master Node FSM compliant.  It's either that or re-parse the message for a matching apdu and invoke id, and then defer if the next message does not match.  The problem happens when an unconfirmed request (i.e. WhoIs) is followed immediated by a confirmed request (i.e. ReadProperty) before the device can respond to the unconfirmed request (i.e. the I-Am is queued in the Transmit buffer).

bacnet-stack/ports/win32/mstp.h

@@ -42,55 +42,6 @@
 #include "bacdef.h"
 #include "dlmstp.h"
 
-/*  The value 255 is used to denote broadcast when used as a */
-/* destination address but is not allowed as a value for a station. */
-/* Station addresses for master nodes can be 0-127.  */
-/* Station addresses for slave nodes can be 127-254.  */
-#define MSTP_BROADCAST_ADDRESS 255
-        
-/* MS/TP Frame Type */
-/* Frame Types 8 through 127 are reserved by ASHRAE. */
-#define FRAME_TYPE_TOKEN 0
-#define FRAME_TYPE_POLL_FOR_MASTER 1
-#define FRAME_TYPE_REPLY_TO_POLL_FOR_MASTER 2
-#define FRAME_TYPE_TEST_REQUEST 3
-#define FRAME_TYPE_TEST_RESPONSE 4
-#define FRAME_TYPE_BACNET_DATA_EXPECTING_REPLY 5
-#define FRAME_TYPE_BACNET_DATA_NOT_EXPECTING_REPLY 6
-#define FRAME_TYPE_REPLY_POSTPONED 7
-/* Frame Types 128 through 255: Proprietary Frames */
-/* These frames are available to vendors as proprietary (non-BACnet) frames. */
-/* The first two octets of the Data field shall specify the unique vendor */
-/* identification code, most significant octet first, for the type of */
-/* vendor-proprietary frame to be conveyed. The length of the data portion */
-/* of a Proprietary frame shall be in the range of 2 to 501 octets. */
-#define FRAME_TYPE_PROPRIETARY_MIN 128
-#define FRAME_TYPE_PROPRIETARY_MAX 255
-/* The initial CRC16 checksum value */
-#define CRC16_INITIAL_VALUE (0xFFFF)
-
-/* receive FSM states */
-typedef enum {
-    MSTP_RECEIVE_STATE_IDLE = 0,
-    MSTP_RECEIVE_STATE_PREAMBLE = 1,
-    MSTP_RECEIVE_STATE_HEADER = 2,
-    MSTP_RECEIVE_STATE_HEADER_CRC = 3,
-    MSTP_RECEIVE_STATE_DATA = 4
-} MSTP_RECEIVE_STATE;
-
-/* master node FSM states */
-typedef enum {
-    MSTP_MASTER_STATE_INITIALIZE = 0,
-    MSTP_MASTER_STATE_IDLE = 1,
-    MSTP_MASTER_STATE_USE_TOKEN = 2,
-    MSTP_MASTER_STATE_WAIT_FOR_REPLY = 3,
-    MSTP_MASTER_STATE_DONE_WITH_TOKEN = 4,
-    MSTP_MASTER_STATE_PASS_TOKEN = 5,
-    MSTP_MASTER_STATE_NO_TOKEN = 6,
-    MSTP_MASTER_STATE_POLL_FOR_MASTER = 7,
-    MSTP_MASTER_STATE_ANSWER_DATA_REQUEST = 8
-} MSTP_MASTER_STATE;
-
 struct mstp_port_struct_t {
     MSTP_RECEIVE_STATE receive_state;
     /* When a master node is powered up or reset, */
@@ -141,7 +92,12 @@ struct mstp_port_struct_t {
     /* An array of octets, used to store octets as they are received. */
     /* InputBuffer is indexed from 0 to InputBufferSize-1. */
     /* The maximum size of a frame is 501 octets. */
-    uint8_t InputBuffer[MAX_MPDU];
+    /* FIXME: assign this to an actual array of bytes! */
+    /* Note: the buffer is designed as a pointer since some compilers 
+       and microcontroller architectures have limits as to places to
+       hold contiguous memory. */
+    uint8_t *InputBuffer;
+    uint16_t InputBufferSize;
     /* "Next Station," the MAC address of the node to which This Station passes */
     /* the token. If the Next_Station is unknown, Next_Station shall be equal to */
     /* This_Station. */
@@ -202,13 +158,16 @@ struct mstp_port_struct_t {
     /* less than or equal to 127. If Max_Master is not writable in a node, */
     /* its value shall be 127. */
     unsigned Nmax_master;
-
-    /* An array of octets, used to store PDU octets prior to being transmitted. */
-    /* This array is only used for APDU messages */
-    uint8_t TxBuffer[MAX_MPDU];
-    unsigned TxLength;
-    bool TxReady;               /* true if ready to be sent or received */
-    uint8_t TxFrameType;        /* type of message - needed by MS/TP */
+    
+    /* An array of octets, used to store octets for transmitting */
+    /* OutputBuffer is indexed from 0 to OutputBufferSize-1. */
+    /* The maximum size of a frame is 501 octets. */
+    /* FIXME: assign this to an actual array of bytes! */
+    /* Note: the buffer is designed as a pointer since some compilers 
+       and microcontroller architectures have limits as to places to
+       hold contiguous memory. */
+    uint8_t *OutputBuffer;
+    uint16_t OutputBufferSize;
 };
 
 #define DEFAULT_MAX_INFO_FRAMES 1
@@ -239,14 +198,14 @@ extern "C" {
     /* returns true if line is active */
     bool MSTP_Line_Active(volatile struct mstp_port_struct_t *mstp_port);
 
-    unsigned MSTP_Create_Frame(
+    uint16_t MSTP_Create_Frame(
         uint8_t * buffer,        /* where frame is loaded */
-        unsigned buffer_len,    /* amount of space available */
+        uint16_t buffer_len,    /* amount of space available */
         uint8_t frame_type,     /* type of frame to send - see defines */
         uint8_t destination,    /* destination address */
         uint8_t source,         /* source address */
         uint8_t * data,         /* any data to be sent - may be null */
-        unsigned data_len);     /* number of bytes of data (up to 501) */
+        uint16_t data_len);     /* number of bytes of data (up to 501) */
 
     void MSTP_Create_And_Send_Frame(
         volatile struct mstp_port_struct_t *mstp_port,  /* port to send from */
@@ -254,7 +213,7 @@ extern "C" {
         uint8_t destination,        /* destination address */
         uint8_t source,             /* source address */
         uint8_t * data,             /* any data to be sent - may be null */
-        unsigned data_len);
+        uint16_t data_len);
 
 #ifdef __cplusplus
 }