The Arduino Nano and Uno are equipped with very similar processors (the chip that essentially serves as the brain of the board). The Nano features an ATmega328, while the Uno sports an ATmega328P.

The Board Overview Now, if we look at the Arduino Uno R4 WiFi development board, we can see that it comes with many hardware upgrades over its predecessor. Here is a part marking image of the Arduino ...

Note: Some pins are not connected on a standard Arduino Uno R3 but still listed so you can use them if you had a custom board. It might also be possible that your ISP header of the 16u2 is flipped 180 ...

Input and Output Each of the 14 digital pins on the Arduino Uno can be used as an input or output, using pinMode (), digitalWrite (), and digitalRead () functions. They operate at 5 volts. Each pin ...

I myself own an Arduino Uno R3 and found that it can simplify my projects development and microcontroller programming, but sometimes I need to know the Arduino pinout. That is why I have written this ...

All the project information is provided under the CC BY-NC-SA 3.0 license. On a related note we covered a Microcontroller cheat sheet which covers AVR devices and ISP pinouts.

Once you’ve done that, you have essentially an Arduino with limited pinout and two onboard LEDs, ... On the other hand if you already have the Arduino, fetch the avr.isp.03 firmware and AVRdude.