SparkFun Forums

[glenk]

Sorry if this question has been asked before but I am new to this forum and new to Arduino.

Suppose I create a circuit project with the Arduino Uno and Breadboard, program it and get
it working through the Arduino.

But now I want to detach the microcontroller chip (atmega328p-pu) from the Arduino Board and
insert it onto the breadboard and make the appropriate attachments to the chip pins that correspond
to the Arduino Board pins.

My question is...Do all of the remaining pins on the chip that I don't use, have to be attached
electrically or can they remain unattached? Thanks.

[Ross Robotics]

It really depends what you are doing with the '328. But for basic use, they can be left floating.

[leon_heller]

It's best to make them outputs and set them low. They will consume less current, and be less susceptible to damage.

[glenk]

Thanks for your feedback - Glen

[Valen]

Those chips usually have more than just digital/analog IO pins. Usually there is an analog reference pin, analog ground and analog vcc that needs to be connected in a certain way to make the analog sensing work correctly. This really is all explained in the atmega328p-pu datasheet. If you go barebones with a microcontroller circuit then you should read it, or at least the important sections.

[n1ist]

Actually, you need to wire up AVcc and AGND even if you aren't using the ADC; that entire port is powered from it.
At a minimum, you need to wire up Vcc, AVcc, GND, AGND and some bypass caps. If you are using the ADC, add a 100n cap from Aref to AGND. If you are using the crystal and caps or ceramic resonator, wire them up. Then wire up what you need for your circuit
/mike