Event Conversion ChaiScripts

The EventsFromOPC-UA and EventsToOPC-UA blocks use ChaiScript expressions in the EventConverterScript property to convert the event from one system to another.

ChaiScript is a strongly typed declarative language with syntax similar to C++. The scripts support the same set of built-in ChaiScript operators and functions that are described in the Chai script documentation.

The EventConverterScript's' can refer to all the source event attributes in the C++ like map<string,any> variable map, with attribute name as the key pointing to the value for that attribute. The script task is to set into similar C++ like map<string,any> variable map of the target event type.

CDP Event Attributes

The CDP Event Attributes are always in the map<string,any> named CDPEvent. In EventsToOPC-UA block this map is read-only and acts as the source for conversion, whereas in EventsFromOPC-UA block this map is writeable and its attributes should be valued by the script. The scripts can refer to all CDP event attributes via this map, including these:

OPC UA Event attributes

The OPC UA Event Attributes are always in the map<string,any> named UAEvent. In EventsFromOPC-UA block this map is read-only and acts as the source for conversion, whereas in EventsToOPC-UA block this map is writeable and its attributes should be valued by the script. The script can refer to all OPC UA attributes via this map, including these:

Example Conversion Script

As an example, the following is the default ChaiScript code in EventsFromOPC-UA block that calculates the CDP event attributes from OPC UA event attributes. You can find the reasoning next to the statements as ChaiScript comments.

// First, calculate CDP Event Code:
CDPEvent["Code"] = 0; // default to zero that means no event will be forwarded to CDP
try {
  if (UAEvent["EnabledState/Id"]) { // check if the event is from OPC UA enabled alarm/condition
    if (UAEvent["ActiveState/Id"]) { // check if the event is from OPC UA activated alarm/condition
      CDPEvent["Code"] |= 0x1; // hexadecimal value for CDP alarm Set event code
    } else {
      CDPEvent["Code"] |= 0x2; // hexadecimal value for CDP alarm Cleared event code
    }
    if (UAEvent["AckedState/Id"]) {
      CDPEvent["Code"] |= 0x4; // hexadecimal value for CDP alarm Acknowledged event code
    }
  }
} catch (e) {} // prevents the script from exiting with an error when UAEvent map values do not exist or their type is not compatible
// For alarms, calculate CDP Event Status and Level:
CDPEvent["Status"] = 0;
try {
  if (UAEvent["EnabledState/Id"]) {
    CDPEvent["Group"] = "OPC-UA-Alarms"; // set group name for OPC UA alarms
    if (UAEvent["ActiveState/Id"]) {
      if (UAEvent["Severity"] < 100) {
        CDPEvent["Status"] |= 0x1; // hexadecimal value for CDP alarm status Notify+Set
        CDPEvent["Level"] = "NOTIFY";
      } else if (UAEvent["Severity"] < 500) {
        CDPEvent["Status"] |= 0x10; // hexadecimal value for CDP alarm status Warning+Set
        CDPEvent["Level"] = "WARNING";
      } else {
        CDPEvent["Status"] |= 0x100; // hexadecimal value for CDP alarm status Error+Set
        CDPEvent["Level"] = "ERROR";
      }
    }
    if (!UAEvent["AckedState/Id"]) {
      if (UAEvent["Severity"] < 100) {
        CDPEvent["Status"] |= 0x10000; // hexadecimal value for CDP alarm status Notify+Unacked
      } else if (UAEvent["Severity"] < 500) {
        CDPEvent["Status"] |= 0x100000; // hexadecimal value for CDP alarm status Warning+Unacked
      } else {
        CDPEvent["Status"] |= 0x1000000; // hexadecimal value for CDP alarm status Error+Unacked
      }
    }
    if (UAEvent["Severity"] < 100) {
      CDPEvent["Level"] = "NOTIFY"; // set CDP alarm level to NOTIFY for OPC UA alarms with severity less than 100
    } else if (UAEvent["Severity"] < 500) {
      CDPEvent["Level"] = "WARNING"; // set CDP alarm level to WARNING for OPC UA alarms with severity less than 500
    } else {
      CDPEvent["Level"] = "ERROR"; // set CDP alarm level to ERROR for OPC UA alarms with severity greater or equal than 500
    }
  }
} catch (e) {}
if (UAEvent.count("Message") > 0) {
  CDPEvent["Text"] = UAEvent["Message"]; // use Message as CDP event Text, when available
}
if (UAEvent.count("Comment") > 0) {
  CDPEvent["Description"] = UAEvent["Comment"]; // use Comment as CDP event Description, when available
}

CDP Event Code Flags

Common event codes used in the CDP framework (note multiple flags can be set at the same time)): Common event codes used in the CDP framework (note that multiple flags can be set at the same time):