embedcalc-mcp

Exact embedded-engineering math for AI agents. An MCP server with 38 deterministic calculators, code generators, and schematic checks — so Claude, Cursor, or any MCP-enabled agent computes CRC check values, CAN timing registers, and struct padding, and reviews schematics for MCU wiring mistakes, instead of hallucinating them.

Why

LLMs are confidently wrong about exactly the math that bricks boards. Ask any model for a CRC-16/MODBUS check value, an STM32 CAN_BTR register for 500 kbit/s @ 36 MHz, or the padded size of a struct — you'll get a plausible-looking wrong answer often enough that you can't trust any of them. The failure mode is the worst kind: the answer looks right.

This server gives the model tools instead. Every tool is a pure, deterministic implementation pinned with test vectors (standard CRC check values, oracle fixtures, IPC/ASTM published numbers — 174 tests).

Install

Claude Code:

Terminal

claude mcp add embedcalc -- npx -y embedcalc-mcp

Claude Desktop / Cursor / any MCP client (JSON config):

config.json

{
  "mcpServers": {
    "embedcalc": { "command": "npx", "args": ["-y", "embedcalc-mcp"] }
  }
}

No API key, no account. Runs locally over stdio. (The optional find_component tool queries embedcalc.com over the network; everything else is offline.)

Tools (38)

Domain	Tools
Code generation	`crc_to_c` (7 presets + custom Rocksoft params → compilable table-driven C with check value) · `regmap_to_c` (LSB-first fields → shift/mask defines + bit-field struct) · `bitfield_macro`
Timing	`can_bit_timing` (bxCAN `BTR` / FDCAN `NBTP` / MCP2515 `CNF1-3`) · `uart_baud` (STM32 `BRR` + error %) · `i2c_timing` (pull-up range + STM32 `TIMINGR`) · `spi_timing` · `i2s_clocks` · `lin_timing` · `rs485_bus` · `modbus_rtu_timing` (t1.5/t3.5) · `ring_buffer_size`
Data representation	`qformat_convert` (Qm.n fixed point) · `ieee754_convert` (float/double, hex↔decimal↔bin) · `number_base_convert` (32-bit two's complement) · `endian_swap` (incl. Modbus BADC/CDAB) · `struct_layout` (C parser → offsets/padding/size, 32-bit MCU model)
Electronics	`eseries_nearest` (E6/E12/E24/E96) · `resistor_code` (color bands + SMD/EIA-96) · `crystal_load_caps` · `lm317` · `attenuator_pad` (T/π) · `junction_temp` · `microstrip_impedance` (IPC-2141) · `pcb_trace_width` (IPC-2221) · `awg_wire` · `ne555` · `dcdc_converter` (buck/boost/inverting) · `op_amp` (gain + bandwidth) · `rc_filter` (1st-order LP/HP cutoff) · `bjt_bias` (voltage-divider operating point) · `mosfet_switch` (low-side conduction + gate drive) · `zener_reg` (shunt regulator)
Components	`find_component` — real, in-stock MPNs + buy links from a computed value (parametric search)
Schematic review	`review_schematic` (deterministic MCU board-rule check: decoupling, bulk cap, floating pins, I2C pull-up, reset, output conflict, power short + interface packs auto-detected from net names — USB ESD/VBUS, CAN termination/transceiver, RS-485 termination/bias, SWD connector/reset, crystal load caps — + polarity & voltage/power derating rules (schema-optional ratings) + STM32F4/STM32F1/ESP32/NuMicro family rules; unevaluable rules reported as `skipped`) · `parse_kicad` (KiCad netlist export → standard schema, auto-parses voltage ratings) · `get_extraction_guide` (schematic image → schema, filled by the vision model) · `list_schematic_rules`

All tool names are prefixed embedcalc_ (e.g. embedcalc_crc_to_c).

Example prompts

"Give me MODBUS CRC-16 as a C function" → table-driven C, check("123456789") = 0x4B37 embedded for on-target verification

"CAN 500 kbit/s on STM32F103, APB1 36 MHz, sample point 87.5%" → CAN_BTR = 0x00050008 (BRP=9, TS1=6, TS2=1)

"How big is struct { uint8_t flags; uint32_t ts; uint16_t id; } on a Cortex-M?" → 12 bytes, 5 of them padding, with the layout table

"Encode −0.25 in Q1.14" / "What float is 0x7FC00000?" / "Nearest E96 to 12.3 kΩ?"

Accuracy

CRC: all 7 presets verified against standard check values for "123456789"
CAN: solver output byte-identical to the interactive calculators at embedcalc.com (oracle fixtures in tests/fixtures/)
IEEE-754 / AWG / IPC: pinned to reference constants and published standard values
struct_layout uses a 32-bit MCU model (pointers 4 B; double/int64 size 8, align 4) — stated in the tool description so the model can caveat it

Run it yourself: npm install && npm run build && npm test (174 tests, includes a stdio end-to-end pass that spawns the built server and calls the tools).

embedcalc.com — the same 60+ calculators as free interactive tools, no AI required
Found a calculation LLMs keep getting wrong? Open an issue — collecting candidates for the next batch.

License

MIT

Embedcalc MCP README