PCB Design - common ground?

[DavidBanner]

I'm currently designing my first batch of PCBs for my lit button strips.

I have 2 modules connected to the PCB: DOUT and the DIN.

a)Can I run the VS from say the DIN and use it for the - of LEDs too?

or

b)do I need to have the VS of the DIN going to the buttons and the VS of the DOUT going to the LEDs?

thanks.

D

[Mr modnaR]

a) is the correct answer.