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LoadConstantsFromFile [LJM User's Guide]

Loads a specified file as the Modbus map and Error constants.


LJM_ERROR_RETURN LJM_LoadConstantsFromFile(const char * FileName)


FileName [in]

The absolute or relative file path to load as the constants. Must null-terminate. "default" maps to the default configuration file ljm_startup_config.json in the constants file location (see Constants file parameters).


LJM errorcodes or 0 for no error.

LJME_CONSTANTS_FILE_NOT_FOUND (1292): FileName did not point to a readable file location.

LJME_INVALID_CONSTANTS_FILE (1293): The file located at FileName was not a valid constants file. LJM_ErrorToString outputs a specific error message.


LJM_LoadConstantsFromFile is an alias for executing LJM_WriteLibraryConfigStringS with LJM_CONSTANTS_FILE as the input Parameter and FileName as the input String:

LJM_WriteLibraryConfigStringS(LJM_CONSTANTS_FILE, FileName)

To load the Modbus constants and error constants separately, use LJM_WriteLibraryConfigStringS with LJM_MODBUS_MAP_CONSTANTS_FILE or LJM_ERROR_CONSTANTS_FILE as the Parameter.


Load the constants file "custom_modbus_map.json"

char ErrorString[LJM_MAX_NAME_SIZE];
int LJMError;
LJMError = LJM_LoadConstantsFromFile("custom_modbus_map.json");
if (LJMError != 0) {
    LJM_ErrorToString(LJMError, ErrorString);
    printf("LJM_LoadConstantsFromFile error: %s\n", ErrorString);
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