Vibecode an RS-485 Sensor Node PCB with AI and Gate Checks

MakeIRL's generator treats a RS-485 sensor node prompt as a self-contained project board. Current status: in envelope needs block.

UART is in the intended envelope, but the current catalog lacks verified RS-485 transceiver, protection, isolation, terminal, and termination blocks, so generation is refused today.

MakeIRL V2 extracts a strict CarrierSpec from the prompt, applies a deterministic scope policy, resolves only cataloged blocks, composes deterministic connectivity and exact-MPN BOM data, emits KiCad artifacts, and runs the manufacturing gate. The language model does not invent pins, topology, parts, placement, routing, or substitutions.

1. Baud, cable/topology/node count, A/B naming, ground conductor, termination and bias location, common-mode range, and fail-safe behavior
2. Exact transceiver and protection blocks, isolation decision, DE/RE control, standby/wake, sensor module, and firmware
3. Input voltage/current, connector MPN and wire-entry view, enclosure, cable shield/ground, coating, mounting, and test harness

Block plan:

• Cataloged controller/module carrier
• Verified RS-485 transceiver plus configurable bias/termination/protection block
• Verified field terminal and optional isolated power/interface blocks within scope

Interfaces: UART logic, RS-485 differential field bus, I²C/GPIO sensor. Power plan: At most 12 V SELV/2 A with verified regulation; isolated conversion or surge topology requires dedicated supported blocks.

• Place protection/transceiver at the terminal, keep A/B together, route surge return away from logic, and preserve isolation spacing if a future block uses it.
• Freeze the board outline, mounting holes, connector faces, component height zones, test access, and keepouts before evaluating generated placement or routing.

Gate checks:

1. S1Generated connectivity and schematic parity. Check A/B from mating view, termination/bias DNP options, transceiver voltage and control pins, protection polarity, ground path, connector order, and sensor address.
2. S1Catalog and exact-MPN provenance. Every RS-485 sensor node block, footprint, pin map, required companion, BOM line, and block-status claim must resolve to the pinned catalog version; the prompt cannot create missing hardware.
3. S2PCB DRC, fabrication profile, and release identity. Run KiCad DRC and schematic parity, compare geometry with one quoted fab profile, regenerate Gerbers/drills/BOM/CPL from the approved revision, and inspect both local and supplier previews.

• Review field common mode, isolation need, surge/ESD, A/B conventions, cable ground/shield, termination topology, fail-safe bias, coating, and compliance.
• A reviewer must check primary datasheets, exact symbol-to-footprint mapping, power and protection, return paths, connector orientation, mechanical fit, test coverage, and every gate waiver before release.

Failure modes:

• A/B naming differs across equipment, and fitting termination at every node can overload a bus that worked with only two endpoints.
• ERC and DRC can prove encoded consistency but cannot prove requirements, component source truth, analogue stability, RF/EMI, thermal margin, firmware, safety, compliance, or delivered product function.

Validation plan:

• Test real cable length/node count, reverse A/B, vary termination/bias and ground offset, inject controlled faults/ESD, and verify sensor accuracy and wake.
• Bring up first articles with current limiting, measure every rail before fitting expensive modules, program minimal test firmware, exercise every interface and fault assumption, and retain measurements against the released revision.

• Refuse mains, unsafe isolation claims, unknown field transients, unsupported isolated converters, or invented transceiver/protection blocks.
• UART support alone does not make the external RS-485 physical layer a supported composition.

The intended carrier envelope is 2-layer FR-4, at most 100 × 100 mm, at most 40 BOM lines, at most 12 V SELV and 2 A, with cataloged modules and low-speed I²C, UART, GPIO, slow SPI, or power-only USB-C connections. The current catalog is narrower than that intended envelope.

Deterministic policy refuses unsupported or hazardous requests, including mains, motors, lithium charging, RF design, switch-mode power, high-speed buses, excessive size/current, and unknown modules. A refusal is a safety and truthfulness result, not a failed attempt to improvise a circuit.

The current seed catalog contains ESP32-C3 carrier, USB-C power, and Qwiic/status-LED blocks at checked status. They have passed deterministic checks but are not yet physically verified through the documented two-lot bring-up ladder; pages must not call those current seeds verified.

The output is a gated design candidate for engineering review. Current placement/routing can still produce blocking or review findings, so a generated board is not automatically fab-ready, functionally validated, certified, or safe to order. MakeIRL does not autonomously place a fabrication order from a prompt. Human review, source and output inspection, gate resolution, order-specific fab confirmation, and physical bring-up remain required.