Calculator App

A simple 4-function calculator with floating point support for the Esposito OS.

Features

• Basic Operations: Addition, subtraction, multiplication, division
• Floating Point: Uses hardware-accelerated float operations via ESP32 FPU
• Touch Interface: Large, touch-friendly buttons optimized for the ESP32 CYD touchscreen
• Keyboard Support: Full keyboard input including BBQ20 keyboard support
• Display: Large, bright green display using scaled text rendering
• Memory Functions: Clear, sign toggle (+/-), and percentage operations

Calculator Layout

┌─────────────────────────────────────┐
│ Calculator                          │
│                                     │
│         [ Large Display Area ]       │
│                                     │
│  ┌───┐┌───┐┌───┐┌───┐              │
│  │ C ││+/-││ % ││ / │              │
│  └───┘└───┘└───┘└───┘              │
│  ┌───┐┌───┐┌───┐┌───┐              │
│  │ 7 ││ 8 ││ 9 ││ * │              │
│  └───┘└───┘└───┘└───┘              │
│  ┌───┐┌───┐┌───┐┌───┐              │
│  │ 4 ││ 5 ││ 6 ││ - │              │
│  └───┘└───┘└───┘└───┘              │
│  ┌───┐┌───┐┌───┐┌───┐              │
│  │ 1 ││ 2 ││ 3 ││ + │              │
│  └───┘└───┘└───┘└───┘              │
│  ┌───┐┌───┐┌───────────┐           │
│  │ 0 ││ . ││     =     │           │
│  └───┘└───┘└───────────┘           │
└─────────────────────────────────────┘

Technical Details

• Font Size: 3x scaled text for the display
• Color: Bright green (RGB565: 0x07E0) on black background
• Precision: Single-precision float (32-bit) for hardware FPU acceleration
• Display Format: %.8g format for optimal precision/readability balance
• Button Width: Automatically calculated based on screen size, centered layout
• Touch Coordinates: Properly converts pixel coordinates to character coordinates using font metrics

Keyboard Shortcuts

• Digits 0-9: Number entry
• Operators: +, -, *, /
• Decimal Point: .
• Equals: = or Enter/Return
• Clear: C, c, or ESC
• Sign Toggle: Works through button only
• Percentage: Works through button only

Dependencies

• ui - UI library for button widgets

Floating Point Implementation

This calculator demonstrates Esposito OS's floating point support:

1. Hardware FPU: Uses ESP32 single-precision FPU for fast float operations
2. OS Symbol Table: Math functions exported from firmware to apps
3. No Double Math: Avoids slow software double-precision emulation
4. Direct Display: Uses lovyanGFX scaled text rendering for large numbers

Files

• app.c - Main calculator application
• manifest.cfg - App metadata and configuration
• deps - UI library dependency
• README.md - This file

Building

# Build individual app
bash scripts/build_app.sh -l ui apps/calc/app.c

# Or build all apps
make test

Usage Notes

• The calculator uses standard order of operations (left-to-right for same precedence)
• Division by zero displays "Error"
• Large numbers are displayed in scientific notation when needed
• The display area is automatically cleared when starting new number entry