Bare circuit ?

Hi,

What is the at most basic circuit I need to have in place on a new pcb to: * Boot the arduino chip and have it working

That does not need: * Programming * Serial connection

I just need to power it up, and have it as a input/output device.

Here is a quick scetch I did, does this seem right ? One capacitor for the input power, and one resonator.

Red = a clean 5.0 v Green = GND

you also need to tie reset to +V.

you also need to tie reset to +V.

Through a resistor, about 10K.

Like this right ???

Assuming that large red block is a 10k resistor, yes.

I wouldn't bother connecting AREF (pin 21 or the upper 5V connection on the right hand side of your diagram) to anything. It defaults to 5V internally anyway, having it hard wired to 5V removes the possibility you may want to use a lower external reference voltage in the future.

I wouldn't bother connecting AREF (pin 21 or the upper 5V connection on the right hand side of your diagram) to anything. It defaults to 5V internally anyway, having it hard wired to 5V removes the possibility you may want to use a lower external reference voltage in the future.

Agreed. But make sure you keep AVcc connected to +5V.

If you want to go from "bare" to "totally nude" - I would do away with the external resonator and use the internal 8MHz oscillator which will be just fine for most projects.

Also you can get away without pull-up on reset (the internal weak pull-up is on by default) or disable RESET altogether through fuse settings.

You're then down to just connecting VCC/AVCC and GND/AGND.

disable RESET altogether through fuse settings.

But then you'd have to remove power any time you want to reset...

Although, I suppose that is extremely bare, which was the original goal ;D.

But then you'd have to remove power any time you want to reset...

Reset is useful for prototyping, but less so for finsihed applications.

A WARNING - If you disable reset through fuse settings, the chip can no longer be flashed through ISP (you will then need a high voltage programmer).

you also need to tie reset to +V. Through a resistor, about 10K.

How come Mike? I thought the 10K was just so something like the auto-reset could pull it low. If it's just an operating circuit...

The reset is a high impedance switch so left to its own devices it would be floating and likely to reset at the whim of electrical noise. The 10k pullup is to hold it high, so electrical noise doesn't get a look in. You could wire it straight to 5V but trying to pull it low with a reset switch would fry something....

The reset is a high impedance switch so left to its own devices it would be floating and likely to reset at the whim of electrical noise.

Not so - reset has an internal pullup resistor (30k-60k) to Vcc. For particularly noisy environments however a stronger pullup is recomended.

Atmel has published an application note (AVR042) on the why's and how's related to reset and power hookups.

http://www.atmel.com/dyn/resources/prod_documents/doc2521.pdf

Lm7805, couple caps, a resistor, ceramic crystal. Or leave out lm7805 but power through 5v battery\power supply. I have Built a single sided version cost maybe 10 bucks to make