Hi to all,
I am new here i have desinged a UHF pcb desing. I am working on atmmega128 rf1. i want to know about the pins of microprocessor that are not used .should we ground them???.
Kindly guide me about that.
thanks,

 

Leave unused pins not connected but configure them as output.

 

I like to connect all the unused pins to test points (just a SMD pad or thru-hole) on the PCB. This makes it easy to wire to them later if (when) you find a problem or the sytem requirements change and you need to modify it.

 

Excellent suggestion. I do this too.

 

Thnaks @JMac3108 and @MrChips ...It is written in datasheet that we should add pull up resistors with unused pins avoiding floating value for power consumption

 

Don't they also have WPU (weak pullup) like PICs?

Normally I ignore unused I/O, setting it to output of course allows you to leave it open in any case.

I also often see it on PCBs- some controller pins not connected at all. Never really saw a ring to connect them all or resistor networks even.

An unconnected output should not draw any serious current, consult your datasheet about that (Electrical specifications).

 

Yes, you can add pull-ups and set the pins to inputs. Or you can set the pins to outputs without the pull-ups. You want to avoid floating inputs.