Main Api Functions And Data Flow; Functions Implemented By The Library - ProSoft Technology MVI56E-LDM-MQTT Quick Start Manual

MVI56E-LDM-MQTT ♦ MQ Telemetry Transport
ControlLogix® Platform

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.
ProSoft Technology, Inc.
MQTT-LDM Library
Quick Start Guide
Page 49 of 55