6.4 KiB
NeoECU V1 Hardware Architecture
This document records the current working architecture for the NeoECU V1. It is intended to be refined as the electrical system, engine components, and board packaging are confirmed.
Scope
NeoECU V1 controls a single-piston, four-stroke Eco Marathon engine. The ECU provides engine timing, injection, ignition, sensor acquisition, and CAN telemetry support.
The immediate hardware scope is:
- one injector output
- one dual-ended, two-pin dumb ignition coil output
- crank and cam position inputs
- air and coolant/water temperature inputs
- provision for additional pressure, temperature, and digital inputs
- CAN bus
- a low-current starter-enable output for an external high-current switch
Fuel-pump control is not required because the vehicle fuel system is already pressurised.
Controller
The target controller is the STM32H747 dual-core microcontroller.
- The Cortex-M7 owns deterministic engine control, including trigger capture, synchronisation, and scheduled injection and ignition events.
- The Cortex-M4 is reserved for non-critical work such as telemetry, CAN, and future auxiliary features.
- Timer capture and output-compare resources are used for time-critical engine I/O.
The H747 remains the preferred V1 controller. Its peripheral set provides the required timer, analogue, digital, and FDCAN support with substantial capacity for future telemetry and expansion.
Engine Timing
The current engine timing arrangement is:
| Signal | Current arrangement | Purpose |
|---|---|---|
| Crank | Two Hall-effect pulses per crank revolution | 180-degree position events and speed estimation |
| Cam | One Hall-effect pulse per 720-degree cycle | Four-stroke phase identification |
The initial engine speed limiter is 5,000 RPM. V1 retains the two-pulse crank arrangement. A future four-pulse trigger can provide 90-degree timing events and improve interpolation accuracy, but is not part of the V1 hardware scope.
Crank and cam are dedicated timing interfaces. Their intended 12 V active-low Hall architecture, connector partition, shield treatment, conditioning, and hardware/firmware glitch rejection are defined in ENGINE_POSITION_INPUTS.md.
Power Architecture
The ECU is supplied directly from a 4S LiPo battery. The normal system range therefore includes a fully charged voltage of 16.8 V.
The input power stage must provide:
- input fusing and reverse-polarity protection
- transient protection with voltage ratings suitable for a 16.8 V battery
- protected battery-voltage measurement by the MCU
- a regulated 5 V sensor supply
- a clean regulated 3.3 V rail for the MCU and analogue circuitry
- separate protected power branches for the ignition and injector loads
Coil, injector, and starter-switch current returns must be routed separately from sensor and MCU ground returns, with a deliberate ground strategy joining them at the power-entry region.
Ignition Output
The engine uses a dual-ended, two-pin dumb ignition coil with two spark plugs. The coil primary is supplied from the protected battery rail and switched on the low side by the ECU.
The V1 ignition stage should use an automotive smart ignition IGBT or ignition-driver IC rather than a generic smart low-side switch or a fully discrete IGBT driver. It must be designed for the coil's high-voltage primary flyback and provide active voltage clamping, over-current protection, and thermal protection.
Ignition dwell is adjusted in firmware using measured battery voltage. Current limiting in the ignition driver is required as the safety backstop, particularly at the 16.8 V fully charged battery voltage. Final dwell calibration and the driver rating are pending coil identification or primary-current measurement.
Injection Output
The injector is supplied from the protected battery rail and switched on the low side. Its electrical type has not yet been confirmed, though it is expected to be a conventional high-impedance/saturated injector.
V1 should use an automotive smart low-side injector driver with:
- inductive-load capability and controlled turn-off clamp
- current limit and thermal protection
- open-load and short-circuit diagnostics
- MCU-readable fault reporting
Injector opening-time compensation is performed in firmware from the measured battery voltage. The injector is not supplied from a regulated high-current rail. Its resistance must be measured before the driver and protection values are finalised; a low-impedance injector would require a peak-and-hold driver and changes this architecture.
Sensor and Auxiliary I/O
Analogue inputs should support common 5 V ratiometric sensors, particularly 0.5-4.5 V automotive pressure transducers, as well as thermistor channels. Each input requires protection, filtering, diagnostic-friendly biasing where appropriate, and conditioning to the MCU ADC voltage range.
Initial intended I/O categories are:
| Category | Required V1 capability |
|---|---|
| Digital inputs | Crank, cam, and expansion inputs |
| Analogue inputs | Air temperature, coolant/water temperature, pressure sensors, and expansion inputs |
| Engine outputs | One injector and one ignition-coil primary channel |
| Auxiliary outputs | Starter-enable logic output to an external high-current MOSFET or IGBT switch |
| Communications | One CAN FD vehicle bus with selectable ECU termination; see CAN_PHYSICAL_LAYER.md |
The starter-enable output only commands an external high-current switch. The ECU does not carry the starter's approximately 40 A current.
Decisions Still Required
The following information is needed before schematic capture and component selection are finalised:
- Injector coil resistance and, if available, its part number or datasheet.
- Ignition-coil part number, primary resistance/inductance, and acceptable dwell/current characteristics.
- Required quantity and exact types of spare analogue and digital I/O.
- ECU enclosure, board-size, mounting, environmental, and connector requirements.
- CAN connector family/pin assignment, final cable construction, and endpoint locations; the V1 CAN FD physical-layer basis is defined in CAN_PHYSICAL_LAYER.md.
- Detailed trigger sensor wiring, connector, and cable-length information.
Diagram sources
The architecture figures are embedded as SVGs. Editable sources, PNG previews, and regeneration instructions are in diagrams/.