ComplexCalc

ComplexCalc — Hardware Version 🔌⚡

A standalone embedded calculator for complex n×n linear systems (Ax=b) — no PC required at runtime. Custom STM32F411 PCB with a 16-button keypad and an ILI9341 TFT display, built for electronics students and AC circuit analysis.

[!NOTE] Work in progress. Firmware is functional (keypad input, TFT UI, Gauss-Jordan solver); the PCB is still being routed (some ADC connections are pending — see Design).

📁 Repository Structure

├── code/
│   └── 06ComplexCalcDasProject/   # STM32CubeIDE / CMake firmware project
│       ├── Core/
│       │   ├── Inc/               # ComplexGJ.h (solver), TFT_Screen.h, display_ui.h, ...
│       │   └── Src/                # SWComplexGJ.c (solver), TFT_Screen.c, display_ui.c, main.c, ...
│       └── Drivers/                # Vendored STM32 HAL + CMSIS (ST-generated, not project code)
├── design/
│   └── ComplexCalc/                # KiCad schematic + PCB (in progress)
└── README.md

The actual project logic lives in Core/Inc / Core/Src; everything under Drivers/ is STM32CubeMX-generated boilerplate.

🎯 Overview

• MCU: STM32F411C(C/E)U (Cortex-M4, UFQFPN48) — the same chip used on "BlackPill" dev boards, but here on a custom PCB, you can use the minimum sistem or insert a blackpill in the socket, it works either way.
• Display: ILI9341 TFT over SPI.
• Input: 16-button matrix keypad (4×4), wired directly on the PCB.
• Power: coin-cell battery holder + AMS1117-3.3 LDO regulator.
• Solver: Gauss-Jordan elimination, single-precision (float) complex arithmetic, systems from 2×2 up to 4×4.

No serial terminal, USB host, or PC connection is needed to use the calculator — power it on, and the keypad + screen are the whole interface. (USB/SWD is only used to flash firmware.)

🚀 Build & Flash

Using STM32CubeIDE (recommended):

1. Open STM32CubeIDE.
2. File → Open Projects from File System.
3. Select code/06ComplexCalcDasProject/.
4. Build (Ctrl+B), then flash over USB/SWD (Ctrl+Alt+X).

Using CMake + the ARM GCC toolchain (also supported by this project):

cd code/06ComplexCalcDasProject
cmake --preset Debug      # or: Release
cmake --build --build-preset Debug

This uses the project's own cmake/gcc-arm-none-eabi.cmake toolchain file — you'll need arm-none-eabi-gcc and ninja installed.

🎮 Usage

On power-up, the screen prompts for the system size (2–4). From there:

Once the full A matrix and b vector are entered, the solver runs on-device and the result is shown on screen — no PC needed.

🧮 Solver Details

• Algorithm: Gauss-Jordan elimination (solve_complex_system in ComplexGJ.h/SWComplexGJ.c).
• Precision: single-precision float, EPSILON = 1e-7 for singularity checks.
• Maximum size: 4×4 (N_MAX), matching the keypad-driven size range (2–4).
• Error handling: returns SOLVER_ERR_INVALID_SIZE / SOLVER_ERR_SINGULAR for out-of-range sizes or singular matrices.

🖥️ Design (PCB)

KiCad project at design/ComplexCalc/ — schematic + PCB for the keypad, MCU, TFT header, and power circuitry.

Routing in progress — some ADC-related connections are still pending. A rendered board image will replace this screenshot once the layout is finished.

A datasheet-vs-schematic power supply review (VCAP sizing, VBAT, NRST, HSE crystal value) is available at docs/ComplexCalc-HW_power_supply_review_en.pdf (Spanish version).

🤝 Contributing

1. Firmware changes go in code/06ComplexCalcDasProject/Core/.
2. PCB changes go in design/ComplexCalc/ (KiCad 8+).
3. Open a PR against this repo.

📞 Issues

Report bugs or hardware questions via this repo's Issues.