COS (Calculator OS)

Think different

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Rust-powered embedded calculator with joystick interface

A minimalistic calculator OS for Arduino Nano, using a single vibration motor and a joystick for navigation. Ideal for people with disabilities, educational purposes, or just a unique computing experience.

Features:

• 🦀 Rust for comfort development and embedded safety
• 🔢 Fixed-point arithmetic engine with rounding (supports numbers up to 2^64)
• 🧮 Basic operations (+, -, ×, ÷) and advanced functions (√, x²)
• 🕹️ Joystick-based navigation through virtual keyboard
• 📳 Vibromotor-based numeric output display via blink patterns

Why is the joystick selected?

• Upgrade convenience: changing the behavior of the interface (keyboard layout, navigation logic) is implemented in the firmware — no need to reassemble the electronics, just the firmware.
• Compact: The joystick combines multiple directions and a button in one small component, which reduces size and simplifies installation.

Hardware Requirements:

• Arduino Nano (New Bootloader)
• Joystick module HW-504 (VRx, VRy, SW)
• Vibromotor
• Maybe serial connection for debugging
• And maybe more in future

Usage:

Calculator control is intuitive:

• On power-on, the cursor is on the digit 5 of the virtual keyboard
• Moving the joystick changes the cursor position
• Pressing the joystick activates the current key
• After pressing, the cursor returns to the starting position (digit 5)

Virtual keyboard layout:

                      Constants
                          |
                  sin   φ τ √2
                  cos   γ π e
                  tan √ 7 8 9 ÷
Unary operators —     - 4 5 6 × — Binary operators
                      x²1 2 3 +
                      x³. 0 = -
                      ! C D R
                          |
                  Advanced functions

Key types:

• Digits - input numbers
• Dot - enables fractional input mode
• Equals - gives the result of a binary operation
• Unary operators - trigonometric functions (sin, cos, tan), square root (√), negation (-), square (x²), cube (x³), factorial (!)
• Binary operators - arithmetic primitives
• Constants - insert constants (φ, τ, √2, γ, π, e)
• D (Delete) - remove the last entered character
• C (CE, Clear Entry) - clear the last entered number
• R (Reset) - reset all numbers and the operator
• Advanced functions - varies

Advanced functions may include equation solving using neural networks, photomath, or remembering results of previous calculations, etc.

A more specific layout is defined in the code (configuration will be improved in the future).

Build Instructions

1. Install prerequisites as described in the avr-hal README (avr-gcc, avr-libc, avrdude, ravedude).

2. Run cargo build to build the firmware.

3. Run cargo run to flash the firmware to a connected board. If ravedude fails to detect your board, check its documentation at https://crates.io/crates/ravedude.

4. ravedude will open a console session after flashing where you can interact with the UART console of your board.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Before contribution you need to run cargo clippy --all-features --fix, typos, cargo fmt and cargo sort. For installing typos run cargo binstall typos-cli (or cargo install typos-cli). For installing cargo sort run cargo binstall cargo-sort (or cargo install cargo-sort).

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.