An open-source calculator I made for a school finals project.
All hardware files to make your own CALCKS are in this repository. The PCB design files can be opened with KiCad. The case can be 3D printed with the files found in <Hardware/3D Models>.
To compile this project for AVR architecture, you will need the GCC suite for AVR. For Windows, I used WinAVR.
cd into the Firmware directory of your locally cloned repository and run make eeprom upload. You might need to adjust the used COM port in the Makefile to get avrdude working.