ProSoft Technology MVI69E-LDM-MQTT, Быстрый старт

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MVI69E-LDM-MQTT ♦ MQ Telemetry Transport MQTT-LDM Library
CompactLogix® Platform Quick Start Guide
ProSoft Technology, Inc. Page 48 of 54
10.2 Main API Functions and Data Flow
10.2.1 Functions Implemented by the Library
The functions defined in the header file
C:\Workspace\mqtt-ldm\mqtt-ldm-
lib\inc\mqtt-ldm-lib.h
are shown in the following examples. They are expected
to be called from the user application:
int mqtt_ldm_initialize(const char* path_to_config_file);

This function should be called once at application start-up to initialize internal
structures and start its threads.

Its input argument is a path to the JSON configuration file.

If successful, the function returns 0.
int mqtt_ldm_connect(void);

This function connects to the MQTT broker.

If successful, the function returns 0.
int mqtt_ldm_disconnect(void);

This function disconnects from the MQTT broker.
int mqtt_ldm_is_connected(void);

Returns a non-zero value if a connection to the MQTT broker is established.
int mqtt_ldm_is_connecting(void);

Returns a non-zero value if a connection to the MQTT broker is in progress.
int mqtt_ldm_clean(void);

Frees resources used by the MQTT-LDM library and by the AWS IoT SDK, it should
be called before application exit.
uint32_t get_tick_count(void);

Helper function. Returns number of ticks since computer start, in milliseconds.
int mqtt_ldm_poll(void);

This function must be called by the user application in a continuous loop. It reads the
current value for each tag (by calling function mqtt_read_value ) and if the value is
changed, it publishes it on the MQTT broker.
void ldm_log(enum ldm_log_level log_level, const char *format, ...);

Used by the user application to log messages into log file. Passed arguments are
log-level, C style format string, and optional data to log.