SVGHMI instances configuration¶

Multiple SVGHMI instances can be configured simultaneously in the same Beremiz Configuration Tree, exposing different HMIs.

../_images/svghmi_multi.png

../_images/svghmi_configuration.png

SVGHMI configuration panel

Ports, interfaces, path and MaxConnections¶

Each SVGHMI instance must bind to different interface-port-path triplet. In case of conflict, a build error is issued.

By default, interface is set to localhost, port to 8008 and path is set to Configuration Tree Node’s name: {name}. As an example, in case SVGHMI instance is first node in Configuration Tree, default URL to reach HMI is http://localhost:8008/svghmi_0

Up to MaxConnections clients (i.e. web browser) can connect to the same SVGHMI instance simultaneously. This number has an influence on memory footprint of generated code. In case of repeated connection loss with long TCP TTL, small MaxConnections number can lead to connection refusal.

About Security¶

Watchdog¶

Purpose of SVGHMI watchdog is to detect if HMI is still functioning and connected to PLC. /HEARTBEAT variable is periodically updated by PLC and HMI to detect failure.

When SVHGMI server doesn’t receive HMI heartbeat in due time, watchdog is triggered, and OnWatchdog command is executed. For example, OnWatchdog can be used to restart a new web browser in case it did crash.

Only one single client can use watchdog at a time, and Watchdog configuration setting can be active on only one SVGHMI instance at a time.

WatchdogInitial and WatchdogInterval define how long watchdog will accept to wait before receiving first heartbeat, and then how long it will wait in between heartbeats once first heartbeat has been received.

Starting and stopping browser¶

OnStart and OnStop configuration settings are commands meant control web browser execution when PLC is started or stopped. PID of commands are monitored, and the end of web browser process is awaited after command. If web browser process isn’t finished 3s after calling OnStop command, warning is logged.