OVERVIEW
The PEASI is a graphing calculator based around a large, high resolution e-Paper display and a low power ARM microcontroller running an interactive mathematics engine called EASI. The goal of this project is to create an open-source competitor to current market leaders, namely the TI-84/Nspire series and the HP Prime series. Easy peasy :)
Background
Graphing calculators are an essential educational tool but have seen little change in the last few decades. Despite rapid development of the rest of the technology world, the graphing calculator has maintained a $100+ price tag with little innovation since its introduction in the late 1980s. This is thanks to the lobbying efforts of Texas Instruments and its effective monopoly over the global graphing calculator business. Even Hewlett Packard, once the darling of the scientific calculator world, is reduced to offering its newest HP Prime G2 for the same price as a TI-84 based on a microcontroller first introduced in 1976.
Others have already taken matters into their own hands, introducing online graphing calculators and apps for smartphones. However, this approach has a fatal flaw; students will still have to buy and learn to use a TI (or HP or Casio) because they cannot use internet-enabled devices during exams. While these efforts are certainly laudable and providing crucial functionality to students who cannot afford a $100+ calculator at home, it does little to supplant TI's offerings in schools.
The EASI PEASI project aims to provide an affordable, open-source programmable graphing calculator for educators and professionals alike. By providing the schematics, bill of materials, 3d models for the housing, and software sources for free to all users, anyone could manufacture their own calculator. Anyone would be free to modify any part of the calculator and share these changes with others, thereby contributing to the development of the project.
Goals
These are the goals that we have set for ourselves, listed in order from most to least important:
- Functional parity with current flagship graphing calculators
- Easy to use for students, easy to hack for engineers
- Long battery life and fast charging
- Financial accessibility (~50$ BOM)
Specifications
The parts and numbers given here are still subject to change, but represent the current working model of the device.
- STM32L475VG MCU - Variable 20~80MHz, 128KB RAM, 1MB Flash
- GDEW042T2 ePaper Dispay - 2-color 400x300 4.2in. diagonal
- IL0389 EPD Driver IC - 20MHz 4-wire SPI
- TCPP01-M12 USB-C Protection IC - single-chip CC line protection
- TI bq24093 Li-Po Charger - 1A single cell w/ over-voltage protection
- TI TPS62208 DC-DC Step Down Converter - 93% efficiency @ 3.7V, 10mA
- STC3115 Gas Gauge IC - coulomb counter and voltage measurement IC
- Battery TBD - 1000~2000mAh single-cell Li-Po
- W25N01GV QSPI Flash - 1GB (8x128MB), 50MB/s R/W
- ALPS SKQYAFE010 Tactile Switches - 3.14N actuation force, 0.25mm travel
Task List
This list will be continuously added to and reflects the current development direction. For specifics and the most up-to-date tasks, please refer to the Github issue tracker.
- Port EASI from the TM4C Launchpad to the STM32 Nucleo development board
- Rewrite algebraic equation parser in C++ for stack efficiency and pretty-printing
- Design and fabricate new PCBs around the new MCU
- Add polar and 3D graphing capabilites
- Add more registers and scrolling history to RPN mode