Multiplexing help

  have 2x2x2 led cube made , trying figure out how write code, problem want set digital pins 0, , 1 ground (is possible?). not using transistors ither, have use them make cube work? hope question understandable, thank you.  can post pictures if needed.

when set pin high sources current +5 volt supply though arduino though parts ground
when set pin low sinks current +5 volt supply though parts though arduino , ground

there limitations, dont want source or sink 25-30 milliamps, 40ma absolute maximum individual pin stated datasheet, want wiggle room saftey , tolerances (nothing perfect). not mean can max out each pin , ok, total current package limited 250ma.

so need transistors? depends on setup.

you need limit current going in or out of arduino's pins, , limit current going led's, current on either damage or destroy either part. limit current on led's put resistor in series led, may or may not match arduino limits, , if match them may find light output dimer expected.

in order work around use transistors, typically can handle greater current (you have 1 large part acting single item vs single part thousands if not millions of transistors in it) , , still switched low current, though parts count pretty doubles.

do have schematic of doing?

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