Ganging arduino pins together for increased output

[Gahhhrrrlic]

And therein lies the irony of human ignorance. Answers that are quite often predicated on knowing the questions.

[CrossRoads]

@LarryD

We must remember for very short periods of time inductance and ESR in the cct. we will not see damage if an output is connected to GND.

That flies in the face of the datasheet, which says Absolute Max is 40 mA, and does not provide a time duration. A programming error that leaves on output of for "too long" and poof, the output is blown, and chip failure follows. Good design calls for current limit resistors to protect the outputs as needed.

[CrossRoads]

Make sure the correct datasheet is being used also. The '328PB has lower ratings on the VCC/Gnd pins compared to the '328P.

[LarryD]

The time interval that was being implied is microseconds i.e. if the outputs were switched individually. This was mentioned only as a result of possible shoot through between two pins.

Yes outputs must be protected with resistors !

Personally, two outputs on two ports would be handled with pinMode switching between input to output simulating open drain.

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Edit:
“ Exposure to absolute maximum rating conditions for extended periods may affect device reliability.”

The above statement from the data sheet leaves a whole lot of wiggle room, however, best design (as you mentioned) should always be followed.

[Grumpy_Mike]

@LarryD

“ Exposure to absolute maximum rating conditions for extended periods may affect device reliability.”

Yes it is a typical get out clause, which is saying you use it at this maximum rating for any time and all bets are off. Sadly a lot of non engineers interprete this maximum current to mean you can run it at this lever, and some misinterpreted the limit to mean the Arduino can not supply more current than this and it is safe to connect an LED direct to an output pin.

[Grumpy_Mike]

@Gahhhrrrlic

And therein lies the irony of human ignorance. Answers that are quite often predicated on knowing the questions.

Don’t be silly. You are in a technical forum talking to technical people. I think we do a pretty good job of trying to educate people but we are not mind readers and can’t always plumb the depth of ignorance that lies behind a question, but we give it a damned good try. This sometimes annoys more experienced low count members. Which is why removing the count number from members in this new forum layout is bloody stupid.