I suppose you placed the microflow timer widget inside of a data view with entity MyFirstModule.Machine as data source. The widget requests that you put the enclosing data view’s datasource as parameter in the microflow that your have configured to be called by the widget (MyFirstModule.Map_machine_data). You can just put this parameter (MyFirstModule.Machine) in your microflow even though you might not use it, then it should work.
You can use the microflow timer widget from the appstore to periodically (e.g. every n milliseconds if the service allows – be wary of any rate limits) call this microflow. This widget does not support realtime data streaming, though. This would require another concept, e.g. websockets which is not supported natively by Mendix, but could be implemented in Java. But maybe the microflow timer widget will suite your needs.
I tried that option but it raised one error for me ?