Though the chip can run up to 20MHz, much of the Arduino software assumes a 16MHz clock for timing purposes, so we will stick with that to keep life simple. If you have an extra 0.1uF ceramic capacitor laying around, you can place it across power and ground at pins 7 & 8 to provide some power supply bypassing, but its not really needed for our simple circuit here. For now, connect the following pins on the ATmega328P to the power and ground rails on the breadboard. We are going to use power from the USB port to power our setup. Take note that pin 1 is the pin next to the small dimple in the top of the chip. To begin, insert the ATmega328P chip into the breadboard. If it is not found, the bootloader runs any program that is already stored in memory.įor our example here, we are using a solderless breadboard.

If a new program for download is found, it is downloaded and executed. The bootloader on the chip is a small program that looks to see if a program is ready to be downloaded when the part comes out of reset. To get the chip up and running, you will need to supply 5V power, a 16MHz clock signal, provide a way to reset the chip and a means to interface between the chips serial lines and the USB port on your computer so you can download a program into the part. BUILDING YOUR OWN BARE-BONES UNOīuilding a bare-bones Uno using this chip is easy to do and provides a starting platform that can be expanded upon for more full featured applications. There is something satisfying about building your own microcontroller from scratch, so we are including instructions for building a basic bare-bones system below. To get up and running with a DIY project and be able to download programs with the Arduino IDE, you just need a breadboard and a few parts like a 16MHz crystal and load capacitors and a USB to serial port adapter. Just ensure that you insert it in the same orientation as the old one.

23 total I/O lines including 6 PWM and 6 10-bit ADCīecause these come with the bootloader, if you are replacing a defective chip on an existing Uno board, you just need to pop the old chip out of the socket and replace it with this new one and you are ready to go.

28-pin DIP package is breadboard friendly.

These are perfect for repairing damaged chips on Uno boards or for building a DIY project based on the Uno.

They have the Uno bootloader pre-loaded to make it easy to get up and running. These are ATmega328P microcontroller ICs in the 28-pin DIP package as used on the Arduino Uno.

Atmega328p pinout