PLCHandler Programming Guide - Esco Drives & Automation

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PLCHandler Programming GuideRESULT_PLCHANDLER_INACTIVE: PLCHandler instance isn’t set active (see IniFile).RESULT_RECONNECTTHREAD_STILL_ACTIVE: reconnect thread is still active.RESULT_ITF_NOT_SUPPORTED: the interface isn’t supported.RESULT_ITF_FAILED: the interface can’t start successfully (missing interface dependentDll’s).RESULT_PLC_NOT_CONNECTED: cannot open connection to the PLC.RESULT_PLC_NOT_CONNECTED_SYMBOLS_LOADED: cannot open connection to the PLC butcould load the symbol file offline.2.4 DisconnectionMethod: long ::Disconnect(void)At a call of this method the connection to the PLC will be terminated.Return value: If no error occurs, the function returns RESULT_OK. Otherwise, it returns …RESULT_FAILED: no corresponding interface which can be closed .2.5 Browsing all variables in the PLCMethod: long ::GetAllItems(PlcSymbolDesc **ppSymbolList, unsigned long *pulNumOfSymbols)This method can be used to read the list of all variables which are specified in the PLC.In ppSymbolList a list of all symbols will be returned. For each symbol the list provides name, datatype, address within PLC, variables size in bytes etc.In pulNumOfSymbols the number of variables will be returned.Return value: If no error occurs, the function returns RESULT_OK. Otherwise, it returns …RESULT_FAILED: common error in the underlying interfaces. A specific error code can beretrieved by GetStatus() resp. GetLastError().RESULT_PLC_NOT_CONNECTED: lost connection to the PLC.RESULT_INVALID_PARAMETER: invalid function parameters (for e.g. NULL).The PlcSymbolDesc structure contains the symbolic description of a variable:struct PlcSymbolDesc{char* pszName; symbol name of the variableunsigned long ulTypeId; reference into the symbol type tablechar* pszType; type name of the variableunsigned short usRefId; variable's type (input, output, global, …)unsigned long ulOffset; offset in the memory imageunsigned long ulSize; size of the variablechar szAccess[2]; access type of the variable (no, read, write access, both)unsigned char bySwapSize; basic swap size of the variable};Speciality: The size of a bit symbol is per definition 0 in the CoDeSys runtime system. So you haveto check the symbol's size for 0 and do a special bit coding (for e.g. memset() or memcpy()with parameter size=1 instead with the original symbol's size) 3S - Smart Software Solutions GmbHPLCHandler Programmming Guide.doc Page 6 of 17
PLCHandler Programming Guide2.6 Getting a variables' descriptionMethod: long ::GetItem(char *pszSymbol, PlcSymbolDesc *pSymbol)pszSymbol specifies the variable, for which the description should be retrieved.In pSymbol the description (data type, size in bytes, address etc.) of the variable will be returned.Return value: If no error occurs, the function returns RESULT_OK. Otherwise, it returns …RESULT_FAILED: common error in the underlying interfaces. A specific error code can beretrieved by GetStatus() resp. GetLastError().RESULT_PLC_NOT_CONNECTED: lost connection to the PLC.RESULT_INVALID_PARAMETER: invalid function parameters (for e.g. NULL).2.7 Cyclic Update of Variables2.7.1 Creating a cyclic listMethod: HCYCLIST ::CycDefineVarList(char **ppszSymbols, unsigned long ulNumOfSymbols,unsigned long ulUpdateRate, unsigned long hUpdateReadyEvent = 0,unsigned long hDataChangeEvent = 0, unsigned long hUpdateEvent = 0)This method can be used to create a list of variables, whose values should be updated cyclically bythe PLCHandler and can be read at any time. The method returns a handle for the list. This handlemust be passed with all further method calls.ppszSymbols: Here a list of variable names will be passed.ulNumOfSymbols: This parameter specifies the number of variables in the list.ulUpdateRate: Specifies the update rate for the cyclic update of the variable values.hDataChangeEvent: Here optionally a handle on a event can be specified, referring to which aninformation should be sent at any value change.hUpdateEvent: Here the handle of an event can be passed, which then will be used to control thecyclic update.Return value: If no error occurs, the function returns a handle for the cyclic list. Otherwise, it returns …NULL: function failed. A specific error code can be retrieved by GetStatus() resp.GetLastError().2.7.2 Deleting a cyclic listMethod: long ::CycDeleteVarList(HCYCLIST hCycVarList, int bKeepalive = 1)This method is used to delete a list of variables which had been set up for cyclic update (see above).hCycVarList: Specifies the handle which has been passed by CycDefineVarList().BKeepalive: Here you define, whether the PLCHandler should start a so-called "Keepalive" if thecurrent list is the last cyclic list which gets deleted. In this case typically a thread will be started in thePLCHandler, sending a Keepalive service to the PLC every 2 seconds, in order that the PLC will notlog out if no further services are sent.Return value: If no error occurs, the function returns a handle for the cyclic list. Otherwise, it returns …RESULT_PLC_NO_CYCLIC_LIST_DEFINED: no list to delete. 3S - Smart Software Solutions GmbHPLCHandler Programmming Guide.doc Page 7 of 17
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