Reading and writing analog voltages to two outputs of a lab bench supply from one microcontroller
I would recommend that you isolate the digital control input from the logic in your power supply. This way you will be able to series or parallel connect the PSUs. It will add some complexity but prevent any surprises on your controller or laptop USB port should it be connected.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. A pair of opto-isolators allows complete separation of all circuit grounds.

Just watch your PWM frequency and how the opto-isolators will respond at that frequency. Some will have a slower turn-off time than turn on so the pulse widths may be wider on the receiver than on your transmitter. Check the datasheets.