skarg
7d1550362b
Replace Receive_Packet_Flag conditional variable with a semaphore and update the related library functions accordingly. Analysis of the problem determined that the issue lay in the transfer of APDU packets between the FSM and the APDU packet handler thread. The mechanism previously used by the FSM to notify the APDU packet handler thread that a packet was available for processing used a pthread conditional variable which packet handler thread was supposed to wait on before being signalled by the FSM. However the packet handler thread has other tasks to perform and sometimes was not waiting on the conditional variable which it was signalled. Unlike other synchronisation mechanisms such as semaphores, if the waiting task (the consumer) is not blocked on the conditional variable when the producer signals, then that signal is lost and the consumer is never signalled again, leading to a continual sequence of timeouts on the conditional variable. This in turn led to the packet handler thread never being notified of a packet waiting to be processed thus causing the interface hang. The main problem is that a conditional variable is supposed to be used with a mutex to prevent this behaviour occurring, but this mutex was not present (and in fact had been removed from the code, most likely because it was causing other synchronisation issues) Further inspection revealed that this code was copied from another file but modified to remove the mutex which is an essential part of using a conditional variable for synchronisation. This then prevents the producer task being blocked until the consumer task is waiting on the conditional variable, thus leading to a race condition which is causing the issues seen. The fix is to replace the conditional variable with a semaphore as this provides the required mechanism in this case. Thank you Ian Smith at Abelon Systems Ltd. for the patch! ........
208 lines
7.2 KiB
C
208 lines
7.2 KiB
C
/**************************************************************************
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*
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* Copyright (C) 2012 Steve Karg <skarg@users.sourceforge.net>
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*********************************************************************/
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#ifndef DLMSTP_LINUX_H
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#define DLMSTP_LINUX_H
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#include "mstp.h"
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/*#include "dlmstp.h" */
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#include "bits/pthreadtypes.h"
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#include <semaphore.h>
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#include <stdbool.h>
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#include <stdint.h>
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#include <stddef.h>
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#include "bacdef.h"
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#include "npdu.h"
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#include <termios.h>
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#include "fifo.h"
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#include "ringbuf.h"
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/* defines specific to MS/TP */
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/* preamble+type+dest+src+len+crc8+crc16 */
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#define MAX_HEADER (2+1+1+1+2+1+2)
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#define MAX_MPDU (MAX_HEADER+MAX_PDU)
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/* count must be a power of 2 for ringbuf library */
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#ifndef MSTP_PDU_PACKET_COUNT
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#define MSTP_PDU_PACKET_COUNT 8
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#endif
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typedef struct dlmstp_packet {
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bool ready; /* true if ready to be sent or received */
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BACNET_ADDRESS address; /* source address */
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uint8_t frame_type; /* type of message */
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uint16_t pdu_len; /* packet length */
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uint8_t pdu[MAX_MPDU]; /* packet */
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} DLMSTP_PACKET;
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/* data structure for MS/TP PDU Queue */
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struct mstp_pdu_packet {
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bool data_expecting_reply;
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uint8_t destination_mac;
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uint16_t length;
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uint8_t buffer[MAX_MPDU];
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};
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typedef struct shared_mstp_data {
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/* Number of MS/TP Packets Rx/Tx */
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uint16_t MSTP_Packets;
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/* packet queues */
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DLMSTP_PACKET Receive_Packet;
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DLMSTP_PACKET Transmit_Packet;
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/*
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RT_SEM Receive_Packet_Flag;
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*/
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sem_t Receive_Packet_Flag;
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/* mechanism to wait for a frame in state machine */
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/*
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RT_COND Received_Frame_Flag;
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RT_MUTEX Received_Frame_Mutex;
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*/
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pthread_cond_t Received_Frame_Flag;
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pthread_mutex_t Received_Frame_Mutex;
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pthread_cond_t Master_Done_Flag;
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pthread_mutex_t Master_Done_Mutex;
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/* buffers needed by mstp port struct */
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uint8_t TxBuffer[MAX_MPDU];
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uint8_t RxBuffer[MAX_MPDU];
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/* The minimum time without a DataAvailable or ReceiveError event */
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/* that a node must wait for a station to begin replying to a */
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/* confirmed request: 255 milliseconds. (Implementations may use */
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/* larger values for this timeout, not to exceed 300 milliseconds.) */
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uint16_t Treply_timeout;
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/* The minimum time without a DataAvailable or ReceiveError event that a */
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/* node must wait for a remote node to begin using a token or replying to */
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/* a Poll For Master frame: 20 milliseconds. (Implementations may use */
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/* larger values for this timeout, not to exceed 100 milliseconds.) */
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uint8_t Tusage_timeout;
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/* Timer that indicates line silence - and functions */
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uint16_t SilenceTime;
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/* handle returned from open() */
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int RS485_Handle;
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/* baudrate settings are defined in <asm/termbits.h>, which is
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included by <termios.h> */
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unsigned int RS485_Baud;
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/* serial port name, /dev/ttyS0,
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/dev/ttyUSB0 for USB->RS485 from B&B Electronics USOPTL4 */
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char *RS485_Port_Name;
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/* serial I/O settings */
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struct termios RS485_oldtio;
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/* some terminal I/O have RS-485 specific functionality */
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tcflag_t RS485MOD;
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/* Ring buffer for incoming bytes, in order to speed up the receiving. */
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FIFO_BUFFER Rx_FIFO;
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/* buffer size needs to be a power of 2 */
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uint8_t Rx_Buffer[4096];
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struct timeval start;
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RING_BUFFER PDU_Queue;
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struct mstp_pdu_packet PDU_Buffer[MSTP_PDU_PACKET_COUNT];
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} SHARED_MSTP_DATA;
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#ifdef __cplusplus
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extern "C" {
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#endif /* __cplusplus */
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bool dlmstp_init(
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void *poShared,
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char *ifname);
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void dlmstp_reset(
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void *poShared);
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void dlmstp_cleanup(
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void *poShared);
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/* returns number of bytes sent on success, negative on failure */
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int dlmstp_send_pdu(
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void *poShared,
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BACNET_ADDRESS * dest, /* destination address */
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uint8_t * pdu, /* any data to be sent - may be null */
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unsigned pdu_len); /* number of bytes of data */
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/* returns the number of octets in the PDU, or zero on failure */
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uint16_t dlmstp_receive(
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void *poShared,
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BACNET_ADDRESS * src, /* source address */
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uint8_t * pdu, /* PDU data */
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uint16_t max_pdu, /* amount of space available in the PDU */
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unsigned timeout); /* milliseconds to wait for a packet */
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/* This parameter represents the value of the Max_Info_Frames property of */
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/* the node's Device object. The value of Max_Info_Frames specifies the */
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/* maximum number of information frames the node may send before it must */
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/* pass the token. Max_Info_Frames may have different values on different */
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/* nodes. This may be used to allocate more or less of the available link */
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/* bandwidth to particular nodes. If Max_Info_Frames is not writable in a */
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/* node, its value shall be 1. */
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void dlmstp_set_max_info_frames(
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void *poShared,
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uint8_t max_info_frames);
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uint8_t dlmstp_max_info_frames(
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void *poShared);
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/* This parameter represents the value of the Max_Master property of the */
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/* node's Device object. The value of Max_Master specifies the highest */
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/* allowable address for master nodes. The value of Max_Master shall be */
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/* less than or equal to 127. If Max_Master is not writable in a node, */
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/* its value shall be 127. */
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void dlmstp_set_max_master(
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void *poShared,
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uint8_t max_master);
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uint8_t dlmstp_max_master(
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void *poShared);
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/* MAC address 0-127 */
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void dlmstp_set_mac_address(
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void *poShared,
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uint8_t my_address);
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uint8_t dlmstp_mac_address(
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void *poShared);
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void dlmstp_get_my_address(
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void *poShared,
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BACNET_ADDRESS * my_address);
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void dlmstp_get_broadcast_address(
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BACNET_ADDRESS * dest); /* destination address */
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/* RS485 Baud Rate 9600, 19200, 38400, 57600, 115200 */
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void dlmstp_set_baud_rate(
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void *poShared,
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uint32_t baud);
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uint32_t dlmstp_baud_rate(
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void *poShared);
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void dlmstp_fill_bacnet_address(
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BACNET_ADDRESS * src,
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uint8_t mstp_address);
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bool dlmstp_sole_master(
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void);
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#ifdef __cplusplus
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}
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#endif /* __cplusplus */
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#endif /*DLMSTP_LINUX_H */
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