Unused Pins
Newzed
Posts: 2,503
I would like to clear up how unused pins should be handled.
Letting an unused I/O float presents no hazard to the pin itself.· It is my understanding that floating ports may or may not draw current, and may contribute to the total current draw of the Stamp.· Can I eliminate this possibility by taking all unused I/O ports low in my program?· I would prefer not to use pullups or pulldowns, since this might prove an inconvenince should I want to use the pins later.
Sid
Letting an unused I/O float presents no hazard to the pin itself.· It is my understanding that floating ports may or may not draw current, and may contribute to the total current draw of the Stamp.· Can I eliminate this possibility by taking all unused I/O ports low in my program?· I would prefer not to use pullups or pulldowns, since this might prove an inconvenince should I want to use the pins later.
Sid
Comments
I also prefer not to use pull-ups on unused pins as that adds time and resouces when there is a software solution.
There is also the school of thought to put 220 ohms in series with any output pin, but again, time and resources.
This probably comes down to personal taste......
I make unused pins outputs and drive them low.
However, the pin is not completely protected for a +5v wire touching the pin.
On the other hand, taking the unused input high, I beleive, is not as good. Now the pin is sitting there at 5v exposed to any ground.
I think is is far more likely that ground will contact an unused terminal or trace, than a positive voltage (jumper wire etc).
In summary, I always make unused pins outputs and make them low.
Sid