Streams and functions

To create a new stream/function you only need to inherit secsgem.secs.functionbase.SecsStreamFunction. Three members need to be overridden: _stream, _function and _formatDescriptor.

The last one defines the structure of the data transferred for the stream/function.

For example you want to allow the UNITS field of stream to not only be a string, but any type. You create a new class and define the format descriptor:

class SecsS01F12_New(secsgem.SecsStreamFunction):
    _stream = 1
    _function = 12

    _formatDescriptor = secsgem.SecsVarArray(secsgem.SecsVarList(OrderedDict((
        ("SVID", secsgem.SecsVarU4(1)),
        ("SVNAME", secsgem.SecsVarString()),
        ("UNITS", secsgem.SecsVarDynamic([])),
    )), 3))

To see how to integrate that into the handlers, see the next page Handlers