• Installed inside a SendCutSend-style metal enclosure in a job-site/off-grid power system.
• Controls engine-related functions, monitors sensors, and provides connectivity through the CM5.
• Designed for vibration, EMI, field wiring, and small-to-medium volume production.

• Host a Raspberry Pi CM5 as the main Linux control computer.
• Provide protected wide-range DC input for 12 V to 60 V nominal battery systems.
• Generate clean 5 V for the CM5 and peripherals and local 3.3 V for support ICs.
• Provide CAN for future motor controller and alternator/current telemetry.
• Drive 3 to 4 optically isolated high-side engine-control outputs rated at least 5 A to 8 A per channel.
• Preserve kernel I2C-1 on GPIO2/GPIO3 for PCA9685 and future sensors.
• Provide a separate bit-banged I2C interface for Predator engine data sniffing.
• Expose field-ready connectors, debug UART, status LEDs, sensor expansion, and test points.

• CM5 mezzanine socket and required boot/reset support.
• Wide input protected power front end with reverse polarity, 80 V to 100 V transient protection, surge/TVS, filtering, and fused input.
• High-current 5 V buck rail sized for CM5 peak current with margin.
• Local 3.3 V rail for CAN controller, I2C support, LEDs, and logic.
• SPI CAN controller plus isolated rugged CAN transceiver interface.
• Jumper-selectable 120 ohm CAN termination.
• Three to four optically isolated high-side relay/load driver outputs for engine start, kill, fuel pump, and spare.
• Primary I2C, secondary bit-banged I2C, UART debug, ADC/sensor inputs, status LEDs, and expansion header.

Diagram

• Use official Raspberry Pi CM5 compatible board-to-board connectors and mechanical keepouts.
• Provide CM5 5 V power pins with bulk capacitance close to the connector and distributed high-frequency decoupling.
• Include RUN/reset control, boot mode access, EEPROM/boot configuration access if required by final CM5 reference design, and debug UART.
• Keep high-speed CM5 interfaces optional unless required later; this revision focuses on GPIO, SPI, I2C, UART, and power/control I/O.

• Input connector: Anderson/XT-style connector, large pluggable terminal block, or equivalent field-serviceable connector rated for the selected current and voltage.
• Input protection: fuse or eFuse, high-power TVS/load-dump clamp, reverse polarity ideal-diode MOSFET, common-mode/differential EMI filtering, bulk electrolytic/polymer capacitance.
• Main regulator: automotive/industrial wide-input buck to 5 V.
• Support regulator: 5 V to 3.3 V buck or LDO depending final current and thermal budget.

• TI LM5146-Q1, LM5164-Q1, LM76003-Q1, or LM76005-Q1 for wide-input buck options.
• Analog Devices LT8640S or LT8609S for robust high-efficiency buck alternatives.
• TI TPS7A20, TPS7A47, or AP7365 class LDO only if 3.3 V support current is low enough thermally.
• SMCJ/SM8S/automotive load-dump TVS or surge stopper selected for 80 V to 100 V transient tolerance.

• 5 V rail target: at least 5 A available for CM5 peak load plus peripherals.
• 3.3 V support rail target: 0.5 A to 1.0 A pending final I/O count.
• Input voltage target: 12 V to 60 V nominal battery systems. Regulator and protection design target is 9 V to 60 V continuous operating input with survival/protection for 80 V to 100 V transients and reverse polarity.

• Use MCP2518FD over SPI if CAN FD or more modern support is desired.
• Use MCP2515 only if compatibility with the current Waveshare-style Linux setup is the priority.
• Use isolated CAN because the CAN harness is near the engine and motor controller. Preferred candidates include ADM3053, ISO1042, ISO1050, or an equivalent isolated CAN transceiver/isolation plus isolated DC/DC solution.
• Add ESD/TVS protection on CAN_H and CAN_L.
• Add 120 ohm termination selectable by jumper or DIP switch.
• Connector: rugged pluggable screw terminal or M12-style connector: CAN_H, CAN_L, isolated CAN_GND, optional shield/chassis.

• SPI0_SCLK, SPI0_MOSI, SPI0_MISO, SPI0_CS_CAN
• CAN_INT, CAN_STBY, CAN_RST
• CAN_H, CAN_L, CAN_GND, CAN_TERM_EN

• Use 3 to 4 optically isolated high-side outputs or relay-plus-opto channels rated at least 5 A to 8 A per channel.
• Use 4 channels where board area allows: ENGINE_START, ENGINE_KILL, FUEL_PUMP, RELAY_SPARE.
• Add flyback suppression for inductive loads, output transient clamps, per-channel status/diagnostic where practical, and default-off input pull-downs.
• Keep the CM5 logic domain isolated from the engine/load domain where practical.
• Field connector should be a high-current pluggable screw terminal or rugged circular connector with clear silk labels.

• Infineon PROFET family high-side switches for 5 A to 8 A automotive-style loads, paired with digital optocouplers or isolated gate/control interface if needed.
• TI TPS1H100-Q1/TPS1H200A-Q1 class protected high-side switches where channel current and thermal limits fit the load.
• Automotive relay plus optocoupler input stage if true dry-contact or high-isolation behavior is preferred over solid-state switching.
• Toshiba TLP236x/TLP293 or Broadcom/Avago digital optocouplers for CM5-to-field isolation, selected after input current and timing are checked.

• RELAY_START_CMD, RELAY_KILL_CMD, RELAY_FUEL_CMD, RELAY_AUX_CMD
• RELAY_START_OUT, RELAY_KILL_OUT, RELAY_FUEL_OUT, RELAY_AUX_OUT
• FIELD_12V_RELAY, RELAY_GND

• Preserve CM5 GPIO2/GPIO3 as kernel i2c-1.
• Use pullups to the local 3.3 V rail unless an external bus voltage is needed.
• Add series resistors and ESD protection if routed off-board.
• PCA9685 can remain on i2c-1 with address selection jumpers or pads.
• Provide an I2C expansion connector with 3V3, GND, SDA, SCL, optional 5V.

• I2C1_SDA, I2C1_SCL
• PCA9685_OE, PCA9685_INT if used

• Keep on separate CM5 GPIOs from i2c-1.
• Route to a dedicated Predator engine data connector.
• Add configurable pullups, series resistors, and ESD protection.
• Consider high-impedance buffering if this is truly a passive sniffer and must not disturb the engine bus.

• PRED_I2C_SDA_SNIFF, PRED_I2C_SCL_SNIFF
• PRED_SNIFF_EN, PRED_GND

• Provide field connectors for fuel level, temperature, current sense, and spare analog/digital inputs.
• CM5 has no native ADC, so add an external ADC if analog field sensors are required.
• Suggested ADC: ADS1115 for low-speed precision I2C analog inputs, or ADS7128/ADS7138 if more channels are needed.
• Add input protection: series impedance, RC filtering, ESD/TVS, and clamp strategy matched to sensor range.

• ADC_FUEL_LEVEL, ADC_TEMP_EXT, ADC_CURRENT_ALT, ADC_SPARE1
• SENSOR_5V, SENSOR_3V3, SENSOR_GND

• UART console header: 3V3, GND, UART_TX, UART_RX.
• Status LEDs: PWR_5V, PWR_3V3, ACTIVITY, CAN_ACTIVITY, RELAY_ACTIVE.
• Test points for VIN_PROT, 5V_SYS, 3V3_LOGIC, GND, CAN_H, CAN_L, SPI lines, I2C lines, relay outputs.
• Clear silkscreen labels and connector pin numbering.

Diagram

• Production-intent SMD assembly.
• 4-layer PCB recommended: Top signal/component, Inner 1 solid GND, Inner 2 power/signal, Bottom signal/component.
• Use locking, field-serviceable connectors for field wiring: pluggable screw terminals or rugged M12-style for CAN and signals; Anderson/XT-style or large terminals for main power.
• Provide large test points for factory bring-up.
• Prefer components with good distribution availability and automotive/industrial temperature options where possible.

• Target packing envelope: 8.15 in x 6.75 in x 1.52 in, approximately 207.0 mm x 171.5 mm x 38.6 mm.
• Board should stay comfortably inside this volume with connector bend radius, mounting hardware, vibration isolation, and cable service loops accounted for.

• Initial board target: approximately 160 mm x 110 mm to 180 mm x 125 mm, leaving margin inside the 207 mm x 171.5 mm enclosure area for connectors and wiring.
• Four corner M3 mounting holes with vibration isolation clearance, keepout rings, and chassis/earth strategy defined.
• CM5 centered or slightly offset for thermal clearance and access.
• Field connectors on board edges only where practical to simplify harnessing and panel access.
• Power input and 5 A to 8 A relay/high-side terminals on one high-energy edge.
• CAN and sensor/debug connectors separated from noisy relay/power terminals.

• CM5 connector near center, with keepout and thermal path.
• 5 V buck near power input edge, with short hot-loop and wide copper.
• 3.3 V regulator near logic loads.
• CAN controller close to CM5 SPI pins; CAN transceiver close to CAN connector.
• Relay drivers close to relay connector; keep field/load current away from CM5 and I2C.
• I2C/ADC/sensor front end near sensor connector, away from buck switching node.
• Test points along board edge or between functional blocks.

• Use CM5 as the only main processor; no secondary MCU unless later needed for safety interlock or real-time shutdown.
• Keep kernel I2C and Predator sniffing buses physically and logically separate.
• Prefer MCP2518FD plus isolated CAN transceiver such as ADM3053 or ISO1042 for a modern robust CAN implementation; use MCP2515 only if software compatibility is more important than CAN FD capability.
• Include external ADC because CM5 does not provide native analog inputs.
• Use optically isolated high-side relay/load outputs rather than bare GPIO-driven transistors for field robustness.
• Use a wide-input buck for 5 V; never derive CM5 5 V through a linear regulator.

• Exact surge standard and waveform for the 80 V to 100 V transient requirement.
• Required 5 V current headroom for CM5 peripherals and any USB devices.
• Whether the 5 A to 8 A relay/high-side channels switch battery positive directly or energize external relay coils.
• Final connector family choices: pluggable screw terminals vs M12-style for each external signal group and Anderson/XT vs large terminals for main power.
• Final enclosure mounting hole pattern and usable panel-edge connector locations.
• Whether analog sensors are 0 V to 3.3 V, 0 V to 5 V, resistive, 4 mA to 20 mA, or automotive sender style.

• Updated architecture with confirmed optically isolated 5 A to 8 A high-side/relay outputs, isolated CAN, 12 V to 60 V nominal input, 80 V to 100 V transient protection, reverse polarity protection, field-serviceable connector preferences, and 8.15 in x 6.75 in x 1.52 in enclosure packing envelope.
• Current Flux project had no schematic components or nets at the time of this architecture draft.
• Next step after review: select exact CM5 connector, power regulator, CAN controller/transceiver, relay driver topology, ADC, and rugged connectors; then create the schematic blocks with datasheet-verified wiring.