ATMEGA328P Question

Hi all

I'm going to have a go at making my own pro mini as I have a few projects that need shrinking down a bit (slightly smaller than a pro mini). I've done some research and have ordered all the necessary components, or so I hope. And i've got a lingering question that I can't quite find an answer to that I'm hoping someone here might be able to help with.

I've purchased a handful of ATMEGA328P-AU-ND chips (from Digikey) and the descriptions say they are running at 20 Mhz. Now when it comes to loading the Arduino bootloader / sketches do I need to manually do anything to the fuses? I'm going to be making two boards, the first at 5v - 16Mhz and and the second at 3.3v - 8Mhz, can I just assume that it will be as simple as using 2 different chrysalis then load a sketch? or do I need to dive a little deeper?

I admit that I don't quite understand what the fuses do but have often seen them mentioned when it comes to the running speed.

Apologies in advance if I've asked a silly question and there is already an answer out there somewhere. But I will appreciate any advice you have to offer :slight_smile:

Installing the Arduino Boot Loader ...

https://learn.sparkfun.com/tutorials/installing-an-arduino-bootloader/overview

If you use the Arduino IDE to burn the bootloader this will also set the fuses to their correct value. Other means of burning the bootloader may not perform that step so there is more to know and understand if you go off the reservation. :wink:

mrsummitville - thanks for the guide, it will no doubt come in handy along the way :slight_smile:
retrolefty, thanks!! that was pretty much the confirmation i was looking for, I'm planning on using the Arduino IDE so phew!

Thanks very much guys!!!

If you're making a bunch of these, get a real tool for programming them. I use Atmel AVR ISP MKii, can also recommend Nick Gammon's Arduino as ISP.

lilsancho:
I'm going to be making two boards, the first at 5v - 16Mhz and and the second at 3.3v - 8Mhz, can I just assume that it will be as simple as using 2 different chrysalis then load a sketch? or do I need to dive a little deeper?

If you don't need the ~50ppm accuracy of a crystal, you can use the 8Mhz internal RC oscillator. Besides saving a dime for the crystal you'll free up PB6 & PB7.