Added extra sub-state for MS/TP from Addendum 135-2008v. Tested with ports/bdk-atxx4-mstp/ code on the BACnet Development Kit. Clean compile on src/mstp.c, ports/at91sam7s and ports/atmega168, but untested. All other changes were not compiled or tested.

bacnet-stack/ports/at91sam7s/dlmstp.c

@@ -866,9 +866,19 @@ static bool MSTP_Master_Node_FSM(
                 /* before passing the token.  */
                 Master_State = MSTP_MASTER_STATE_USE_TOKEN;
                 transition_now = true;
-            }
+            } else if ((MSTP_Flag.SoleMaster == false) &&
-            /* Npoll changed in Errata SSPC-135-2004 */
+                (Next_Station == This_Station)) {
-            else if (TokenCount < (Npoll - 1)) {
+                /* NextStationUnknown - added in Addendum 135-2008v-1 */
+                /*  then the next station to which the token
+                    should be sent is unknown - so PollForMaster */
+                Poll_Station = next_this_station;
+                MSTP_Send_Frame(
+                    FRAME_TYPE_POLL_FOR_MASTER, Poll_Station,
+                    This_Station, NULL, 0);
+                RetryCount = 0;
+                Master_State = MSTP_MASTER_STATE_POLL_FOR_MASTER;
+            } else if (TokenCount < (Npoll - 1)) {
+                /* Npoll changed in Errata SSPC-135-2004 */
                 if ((MSTP_Flag.SoleMaster == true) &&
                     (Next_Station != next_this_station)) {
                     /* SoleMaster */

bacnet-stack/ports/atmega168/dlmstp.c

@@ -783,6 +783,17 @@ static bool MSTP_Master_Node_FSM(
                 /* before passing the token.  */
                 Master_State = MSTP_MASTER_STATE_USE_TOKEN;
                 transition_now = true;
+            } else if ((MSTP_Flag.SoleMaster == false) &&
+                (Next_Station == This_Station)) {
+                /* NextStationUnknown - added in Addendum 135-2008v-1 */
+                /*  then the next station to which the token
+                    should be sent is unknown - so PollForMaster */
+                Poll_Station = next_this_station;
+                MSTP_Send_Frame(
+                    FRAME_TYPE_POLL_FOR_MASTER, Poll_Station,
+                    This_Station, NULL, 0);
+                RetryCount = 0;
+                Master_State = MSTP_MASTER_STATE_POLL_FOR_MASTER;
             }
             /* Npoll changed in Errata SSPC-135-2004 */
             else if (TokenCount < (Npoll - 1)) {

bacnet-stack/ports/bdk-atxx4-mstp/dlmstp.c

@@ -888,6 +888,17 @@ static bool MSTP_Master_Node_FSM(
                 /* before passing the token.  */
                 Master_State = MSTP_MASTER_STATE_USE_TOKEN;
                 transition_now = true;
+            } else if ((MSTP_Flag.SoleMaster == false) &&
+                (Next_Station == This_Station)) {
+                /* NextStationUnknown - added in Addendum 135-2008v-1 */
+                /*  then the next station to which the token
+                    should be sent is unknown - so PollForMaster */
+                Poll_Station = next_this_station;
+                MSTP_Send_Frame(
+                    FRAME_TYPE_POLL_FOR_MASTER, Poll_Station,
+                    This_Station, NULL, 0);
+                RetryCount = 0;
+                Master_State = MSTP_MASTER_STATE_POLL_FOR_MASTER;
             }
             /* Npoll changed in Errata SSPC-135-2004 */
             else if (TokenCount < (Npoll - 1)) {

bacnet-stack/ports/dos/dlmstp.c

@@ -884,6 +884,17 @@ static bool MSTP_Master_Node_FSM(
                 /* before passing the token.  */
                 Master_State = MSTP_MASTER_STATE_USE_TOKEN;
                 transition_now = true;
+            } else if ((MSTP_Flag.SoleMaster == false) &&
+                (Next_Station == This_Station)) {
+                /* NextStationUnknown - added in Addendum 135-2008v-1 */
+                /*  then the next station to which the token
+                    should be sent is unknown - so PollForMaster */
+                Poll_Station = next_this_station;
+                MSTP_Send_Frame(
+                    FRAME_TYPE_POLL_FOR_MASTER, Poll_Station,
+                    This_Station, NULL, 0);
+                RetryCount = 0;
+                Master_State = MSTP_MASTER_STATE_POLL_FOR_MASTER;
             }
             /* Npoll changed in Errata SSPC-135-2004 */
             else if (TokenCount < (Npoll - 1)) {

bacnet-stack/ports/pic18f6720/mstp.c

@@ -799,6 +799,17 @@ bool MSTP_Master_Node_FSM(
                 /* before passing the token.  */
                 mstp_port->master_state = MSTP_MASTER_STATE_USE_TOKEN;
                 transition_now = true;
+            } else if ((MSTP_Flag.SoleMaster == false) &&
+                (Next_Station == This_Station)) {
+                /* NextStationUnknown - added in Addendum 135-2008v-1 */
+                /*  then the next station to which the token
+                    should be sent is unknown - so PollForMaster */
+                Poll_Station = next_this_station;
+                MSTP_Send_Frame(
+                    FRAME_TYPE_POLL_FOR_MASTER, Poll_Station,
+                    This_Station, NULL, 0);
+                RetryCount = 0;
+                Master_State = MSTP_MASTER_STATE_POLL_FOR_MASTER;
             }
             /* Npoll changed in Errata SSPC-135-2004 */
             else if (mstp_port->TokenCount < (Npoll - 1)) {

bacnet-stack/ports/rtos32/mstp.c

@@ -938,6 +938,17 @@ bool MSTP_Master_Node_FSM(
                 /* then this node may send another information frame  */
                 /* before passing the token.  */
                 mstp_port->master_state = MSTP_MASTER_STATE_USE_TOKEN;
+            } else if ((mstp_port->SoleMaster == false) &&
+                (mstp_port->Next_Station == mstp_port->This_Station)) {
+                /* NextStationUnknown - added in Addendum 135-2008v-1 */
+                /*  then the next station to which the token
+                    should be sent is unknown - so PollForMaster */
+                mstp_port->Poll_Station = next_this_station;
+                MSTP_Create_And_Send_Frame(mstp_port,
+                    FRAME_TYPE_POLL_FOR_MASTER, mstp_port->Poll_Station,
+                    mstp_port->This_Station, NULL, 0);
+                mstp_port->RetryCount = 0;
+                mstp_port->master_state = MSTP_MASTER_STATE_POLL_FOR_MASTER;
             }
             /* Npoll changed in Errata SSPC-135-2004 */
             else if (mstp_port->TokenCount < (Npoll - 1)) {

bacnet-stack/src/mstp.c

@@ -795,6 +795,17 @@ bool MSTP_Master_Node_FSM(
                 /* before passing the token.  */
                 mstp_port->master_state = MSTP_MASTER_STATE_USE_TOKEN;
                 transition_now = true;
+            } else if ((mstp_port->SoleMaster == false) &&
+                (mstp_port->Next_Station == mstp_port->This_Station)) {
+                /* NextStationUnknown - added in Addendum 135-2008v-1 */
+                /*  then the next station to which the token
+                    should be sent is unknown - so PollForMaster */
+                mstp_port->Poll_Station = next_this_station;
+                MSTP_Create_And_Send_Frame(mstp_port,
+                    FRAME_TYPE_POLL_FOR_MASTER, mstp_port->Poll_Station,
+                    mstp_port->This_Station, NULL, 0);
+                mstp_port->RetryCount = 0;
+                mstp_port->master_state = MSTP_MASTER_STATE_POLL_FOR_MASTER;
             } else if (mstp_port->TokenCount < (Npoll - 1)) {
                 /* Npoll changed in Errata SSPC-135-2004 */
                 if ((mstp_port->SoleMaster == true) &&