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