Modified while testing the AT91SAM7S port. Needed to include MS/TP Silence Timer in ISR, and didn't want to call a function.

bacnet-stack/dlmstp.h

@@ -59,7 +59,9 @@ extern "C" {
 
     bool dlmstp_init(char *ifname);
     void dlmstp_cleanup(void);
-    void dlmstp_millisecond_timer(void);
+
+    /* address of the 16-bit timer.  Update it in an ISR or Task. */
+    volatile uint16_t *dlmstp_millisecond_timer_address(void);
 
     /* returns number of bytes sent on success, negative on failure */
     int dlmstp_send_pdu(BACNET_ADDRESS * dest,  /* destination address */

bacnet-stack/mstp.c

@@ -745,16 +745,16 @@ bool MSTP_Master_Node_FSM(volatile struct mstp_port_struct_t * mstp_port)
             mstp_port->master_state = MSTP_MASTER_STATE_DONE_WITH_TOKEN;
             transition_now = true;
         } else if (mstp_port->SilenceTimer > Tusage_delay) {
-            /* if we missed our timing deadline, another token will be sent */
+            /* Don't send it if we are too late in getting out. */
+            /* Don't worry.  If we missed our timing deadline, 
+               another token will be sent */
             mstp_port->master_state = MSTP_MASTER_STATE_IDLE;
         } else {
-            /* don't send it if we are too late in getting out */
             uint8_t frame_type = mstp_port->OutputBuffer[2];
             uint8_t destination = mstp_port->OutputBuffer[3];
             RS485_Send_Frame(mstp_port,
                 (uint8_t *) & mstp_port->OutputBuffer[0], length);
             mstp_port->FrameCount++;
-            /* last trasmitted frame type */
             switch (frame_type) {
             case FRAME_TYPE_BACNET_DATA_EXPECTING_REPLY:
                 /* SendAndWait */