MightyNanoS with base board - another arduino clone

It always happened that I found my limits with my Arduino Nano. As an alternative, an Arduino Mega would offer, but this is too oversized for my projects. For this reason, I have made my own development, which also accommodates my electronics hobby. I opted for the ATmega 644p. It offers significantly more resources than the ATmega 328, but is priced attractively and well handled by the case for the hobbyist.
The project was developed completely with KiCAD and consists of 2 components.

The first component is the "MightyNanoS", that is the MCU board. The name comes from the used boot loader (Optiboot / MightyCore). However, there is already a MightyNano on the market that is more sophisticated and has more features. But because I only use the absolute necessary components, the "S" was added to the name. This minimal configuration can be used as the heart of many PCBs. The power supply is always taken over by the corresponding project. A protection against reverse polarity of the operating voltage is present (p-channel MOSFET). It might also make sense to use a pin-compatible LDO regulator (e.g. XC6206) in your own PCB project instead of this transistor in order to adapt the MCU to other voltages.
It was also important that the MightyNanoS can be used on breadboards. All signal pins are led out on two pin strips. Thus, simple test circuits can be built and functions tested.

The 2nd component is a base board. It is not always the intention to design a larger PCB. Many projects result from the fact that corresponding sensors or other finished modules are simply networked. For this purpose, the base board was designed. It picks up a MightyNanoS and provides the power supply. All connections are available via pin strips. And because there was still enough space available, I placed some important components for me on the base board. That's one very accurate real-time clock with battery backup (DS3231) included. There is also an EEPROM socket (I2C) and a buzzer. Instead of the DIP socket for the EEPROM, an SOP8 chip can also be soldered directly. 2 additional connections for the I2C bus are available.

Of course, I will not always populate the base board, but only place the really needed components.
 

The dip switch has 2 functions. You can turn the buzzer (connected to D1) on or off. It is also possible to switch the alarm connection of the DS3231 to the INT0 of the MightyNanoS. So you can use previously programmed interrupts triggered by the DS3231.

A USB function is not included. I only need them in the rarest cases. There are USB / TTL converters on the market that can be connected to the UART header of the MightyNanoS. An ICSP connection for programming is also included on the MightyNanoS.

The used SMD components are almost always in the 0805 housing. That's ideal for me. Small enough for compact projects and big enough to handle them properly. The other components are usually easy to get via eBay. A replica should therefore be no problem for the experienced hobbyist.

I recently revised the layout and added a status LED and an LDO regulator (XC6206). The base board now also provides 3.3V. This is useful in order to be able to use 3.3V components with low power requirements. Then a level conversion is also necessary. If, on the other hand, you only want to work with 3.3V, you can also adjust the buck regulator instead (see data sheet of the MP2359) and omit the LDO regulator. (But first you have to test whether the buzzer and its transistor driver work with this low voltage).

My KiCAD project files can be downloaded from my Google Drive

Nano644.zip
Bytes: 1742136
MD5: 97674D885B42AD2C2D6F42CB3085F6FB

SHA256: 4D6951608BD512000D66E411FFC64DB386A4622BC873A308463B6DC5AC04169E

Nano644_Base.zip
Bytes: 1850413
MD5: 47AB3E6345B38C3D6C6B5F60ECD30058

SHA256: 2F83CD8D21CAC8B22110966EB14ED08908D3DABD4B68A65473748CCD54303F65


This board requires the MightyCore bootloader:  
https://github.com/MCUdude/MightyCore

The PIN numbering corresponds to the "MightyCore Standard pinout".

There is another archive in the ZIP files. This can be uploaded directly to a board manufacturer (I use Seedstudio or JLCPCB) to order professional PCBs in your desired color.

My project is free for private use. It is aimed at experienced people. I take no guarantee! Duplication is at your own risk and responsibility!

You are welcome to customize or modify my project and publish it. However, you always have to refer to the origin!