ATmega32U4 Schematic working together with Breakout Boards!

G’day Everyone!

Hope we are all keeping safe during these uncertain times!

A little bit of backstory on what I am trying to create, for some context. I have found that using breakout boards with the traditional Arduino Uno or Nano can sometimes be flimsy or oversized. For quick prototyping, a PCB is typically used to replace these wire connection with pin headers, but I am looking to take this a step further. My plan/idea is to have a ATmega32U4 as the central “Brain” with the “breakout board components” being on the same SMT Assembled PCB (E.g the ATmega32U4 have a OLED, Joystick and NRF24L01 assembled as one).

Currently I have based the “Brain” section of the board on the SparkFun’s Qwicc Pro Micro V2 (

I would greatly appreciate if anyone could suggest any changes or improvements to this base design, before adding the breakout board components.

Stay Safe,

ATmega32U4 Schematic.pdf (96 KB)

If this is your USB input, 5.1K in series with D+ and D- is extremely high. In many cases, I've seen around 27 ohm used.

Your blue LEDs will probably be quite dim, they typically drop about 3.2 volts. With 5V supply and 1K limiting resistor, there will only be 1.8 mA through the LEDs.

I have switched the 5.1K resistor to the 27 ohm resistor as you suggested.

Along with this I have changed the blue LED’s, as you pointed out as they would be dim which was confirmed through the datasheet. I have changed them to white LED’s as they have a broad voltage range along with needing less mA.

I’m assuming that when burning the bootloader that I would use the ICSP pins and the Arduino IDE set to ‘Arduino Leonardo’, as they share the ATmega32u4. Have you found there to be a more successful method?

Also if you could keep an eye out for any issue please let me know.

Thanks for your time, Jayden

Schematic ATmega32U4 V2.pdf (95.9 KB)