A: why do I need two routes? Because manganese copper sampling is adopted for this module, the ground of the whole 

module is on the live line (see the figure below), which has been isolated from the communication module of MCU. The 

power supply of the other module needs to be isolated from the external power supply, so as to prevent damage to the 

external equipment. It is not allowed to use only one circuit in parallel, otherwise the module or external equipment will 

be damaged. Therefore, two power sources must be used for power supply, and one of them must be isolated.

If there is only one power supply, it can be connected as shown in the following figure