NeoECU-Hardware/Architecture

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. A future crank trigger with four pulses per revolution is being considered to provide 90-degree timing events and improve interpolation accuracy.

Crank and cam sensors currently operate as 12 V, active-low Hall-effect signals: their output is normally high and pulls low when active. The ECU must condition these signals to protected 3.3 V timer inputs. The interface must support the existing open-collector-style arrangement and provide noise rejection appropriate for an engine environment.

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	CAN bus with selectable termination

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:

1. Injector coil resistance and, if available, its part number or datasheet.
2. Ignition-coil part number, primary resistance/inductance, and acceptable dwell/current characteristics.
3. Required quantity and exact types of spare analogue and digital I/O.
4. ECU enclosure, board-size, mounting, environmental, and connector requirements.
5. CAN connector and bus topology.
6. Detailed trigger sensor wiring, connector, and cable-length information.