I launched this project when I was in junior middle school (in Jan, 2012). It was firstly called "OurCalc". I thought if I could combine low-cost MCU-based hardwares with open source calculator softwares. Commercial graphing calculators are just too expensive. I started learning designing and programming with MCU then.
After years, here is the forth version of prototype. I used STM32F407VG microcontroller as the main processor, connected to an COG LCD Display. Software is still under development, mainly based on Eigenmath. I have wrote an textbook-like render engine myself, but currently buggy so is not added to the firmware. As I'm now senior 3, I need to get myself admitted by an university (SAT, essay and so on ), so I may not update codes before next year.
I've uploaded firmware, sch and pcb to GitHub avalible for download.