Roadmap

Milestone: Core foundation (v0.1 – v0.4) — complete

• Math engine: Q31.32 fixed-point with CORDIC, minimax, CLZ sqrt, rational atan2
• Lexer: expression string to typed token stream (max 64 tokens)
• Parser: recursive-descent PEMDAS with implicit multiplication
• Evaluator: full operator/function dispatch, sum/int loop aggregates
• Complex numbers: Smith's robust division, all transcendental functions
• Variable storage: Ans + 26 registers A-Z, copy-on-read for loop shadowing
• Statistical distributions: Stirling log-gamma, log-factorial, binomial, Poisson, chi-squared CDF
• Boot layer: vector table, .bss/.data init, Reset handler
• HAL: UART, I2C, GPIO, clock, OLED driver (SSD0303)
• Runtime: event loop, state machine, ANSI escape sequence parser
• UI: 5x7 bitmap font, formula renderer, Sigma/Integral glyphs
• Host-side unit test suite (300 tests)
• Overflow-aware scientific notation display
• Degrees mode (Ctrl+D toggle)

Milestone: Bytecode VM & Matrix/Scientific modes (v0.5 – v0.6) — complete

• Bytecode VM replacing recursive AST evaluator (flat dispatch, 16-entry value stack, zero C stack growth)
• Compiler: recursive-descent emits opcodes into 256 B fixed buffer
• 12 opcodes, CallFunction(u8) deduplicates 22 separate function call opcodes
• Stack overflow eliminated: 1+1+1+1+1+1+1+1+1+1 now works (was silent .bss corruption)
• Matrix type (fixed-size buffer, max 4×4)
• Matrix addition, multiplication, transpose
• Matrix determinant, inverse, cofactor, adjugate
• Matrix literals: [(a,b)(c,d)] syntax
• Matrix registers: MatA, MatB, MatC
• Three-mode cycle (Standard, Advanced, Matrix)
• Scientific notation (Scientific mode): 1.5E+10 syntax, ±99 exponent hard limit
• Scientific arithmetic (multiply, divide, add, subtract, power)
• Auto-conversion to Scalar when value fits Q31.32 exactly
• Four-mode cycle (Standard, Advanced, Matrix, Scientific)
• Overflow sentinel (bypasses LTO-corrupted EvalResult::Overflow enum layout)
• Deduplication: 22 function opcodes → CallFunction(u8), 6 matrix opcodes → CallMatrixFunc(u8)
• Flash: 57,728 B → 63,029 B (96.2%)
• SRAM: 5,088 B → 4,312 B (52.6%)

Short-term

Testing infrastructure

• Test-vector generator script (Python Decimal for exact reference values)
• Property-based tests for arithmetic roundtrips
• Coverage reporting

Math engine hardening

• Fractional display mode ($1/3$ instead of $0.333333$)
• Configurable output precision (3–9 decimal places)
• rand() / RanInt#(a,b) — random number generation
• d/dx(f(x), x, a) — numerical differentiation
• solve(f(x), x, a, b) — numerical root finding

Developer experience

• .vscode/ configuration in repository
• GDB init script for quick debugging setup
• Release build CI artifact (GitHub Actions draft release)

Medium-term

Port to modern hardware

The math engine and runtime are already hardware-independent. Candidate targets:

Target	Core	Flash	RAM	Price
RP2040 (Pi Pico)	Cortex-M0+	2 MB	264 KB	$4
STM32F411	Cortex-M4F	512 KB	128 KB	$8
STM32G431	Cortex-M4F	128 KB	32 KB	$5
ESP32-C3	RISC-V	4 MB	400 KB	$3
ATSAMD51	Cortex-M4F	512 KB	192 KB	$10

For each port: rewrite hal/, update boot.rs + link.x. Zero numcore/ changes.

Reference hardware design

• Open-source KiCad PCB (mechanical keyswitches, OLED, USB-C)
• 3D-printable enclosure
• BOM targeting $20–30
• Cherry MX / Kailh Choc switch support
• Battery charging circuit (LiPo)

Graphing mode

• Function plotting on OLED
• Pan/zoom with register-based viewport
• Multiple simultaneous plots (up to 3)
• Table of values
• Dynamic y-axis scaling

Standalone math crate

• Extract math/ as numcore-math on crates.io
• Platform-agnostic (std and no_std)
• Python/JS bindings for cross-validation

Long-term

Advanced calculator modes

• Unit conversions, physical constants
• Programming mode: HEX/DEC/OCT/BIN, bitwise ops
• Statistics mode: data entry, linear regression
• CAS basics: symbolic differentiation/integration, simplification

Hardware milestones

• CE/FCC-certified reference design
• USB virtual serial port with firmware updates
• SPI flash for persistent storage across reboots
• Low-power mode for battery operation

Ecosystem

• Curriculum alignment (IB, A-level, AP, SAT)
• Open source textbook companion
• Web-based WASM simulator
• Community port catalogue
• Internationalisation (i18n)

Non-goals

• Touchscreen UI — hurts battery life, increases BOM cost, reduces tactility
• Full CAS like Mathematica — calculator-grade scope only
• Proprietary lock-in — open-source hardware (CERN-OHL-S license)
• Mobile app — this is a dedicated hardware project
• Wireless exam cheating vectors — no Wi-Fi/BT in exam modes
• Multi-line expression input — single-line with cursor editing is sufficient for calculator scope