Hello everybody, sorry if this is not the right place to ask this but I've been searching for some hours now without finding any solution. So I bought an arduino (funduino uno) recently and everything was smooth using the included ATMmega328P-U. Today I bought 2 more microcontrollers which are also ATMmega328P-U with the only difference the number on the bottom being 2025SK0 instead of 2043H6B on the "original". Anything I upload to these 2 keeps failing I really have no idea what I'm doing wrong. Thank you!
Sounds like you forgot to burn the bootloader on them!
The Funduino Uno seems very much the same as the official Arduino Uno.
You need a second board to be able to burn the bootloader: https://www.arduino.cc/en/Tutorial/BuiltInExamples/ArduinoISP
Or you can buy the microcontrollers with the boot-loader pre-installed.
What is the purpose of the two additional microcontrollers (why did you buy them)?
So after researching a bit more, (heads up to @missdrew , his/her answer helped a lot as new material for searching) I finally managed to bootload both my ATMega328s and they are both up and running now. I'll post the link of the tutorial that helped me achieve that for any future amateur that may have the same issues I had. If this is not how this forum works feel free to delete it.
A clarification to any newbie following this guide that confused me a bit. You upload the example "ArduinoISP" to the ATMega328 that came with the board and then you disconnect the usb, wire the new ATMega328 on a breadboard to your arduino uno (as shown in the image on the link) without removing the "original" ATMega328 from the board, reconnect the usb and burn the bootloader!
To program them and solder them in circuits. Isn't this the main purpose of Arduino boards?
Could have been that you just wanted spares
In your case, when they are in a dedicated board, you can also straight away flash the sketch via ICSP; no bootloader needed.
Glad that you managed.