• Board X dimension: 101.8 mm
• Board Y dimension: 38.0 mm
• Finished board thickness: 2.0 mm
• Corner radii: 6.25 mm on all four corners (top-left, top-right, bottom-right, bottom-left)
• High-current terminal count: five — battery positive, battery negative, and three motor phases
• Finished plated through-hole diameter for every high-current terminal: 5.75 mm
• Overall plated contact-pad diameter on both PCB sides for every high-current terminal: 11.0 mm minimum
• Resulting radial annular copper width at an 11.0 mm pad diameter: 2.625 mm
• Mounting holes: exactly two through holes, each 2.8 mm diameter; locations must remain exactly as defined by the user-provided STEP
• Mounting-hole centers using the STEP lower-left board datum: H1 = (2.636631 mm, 18.888223 mm) and H2 = (99.156631 mm, 17.904272 mm)
• Equivalent mounting-hole centers using the Flux board-center datum: H1 = (-48.263369 mm, -0.111777 mm) and H2 = (+48.256631 mm, -1.095728 mm)
• The holes are intentionally slightly offset and are not on a common board centerline. Do not center, symmetrize, mirror, or relocate them.
• The user-provided PCB STEP remains the source of truth for the exact board shape and mounting-hole geometry.
• The user-provided terminal-post STEP/drawing remains the source of truth for the five high-current terminal bodies. Generic terminal models are prohibited unless the user explicitly approves a substitution.

• RC boat propulsion and steering/auxiliary servo control.
• Powered directly from a 3S-5S LiPo battery.
• Intended for sealed/waterproof installation with a single-side water-jacket heat sink interface.

• Drive a 3-phase brushless motor at up to 70A continuous.
• Receive Flysky AFHDS 2A commands through an A7105 RF transceiver.
• Decode receiver data on the STM32F405 and use it for motor throttle and servo PWM outputs.
• Provide SWD debug/programming access.
• Monitor battery voltage for cell-count detection and low-voltage cutoff.

• STM32F405RGT6 as the single MCU for ESC control and receiver decoding.
• DRV8302 3-phase gate driver, kept close to the VESC reference design.
• Dedicated onboard servo buck regulator from the main LiPo, targeting 6V output and 5A peak-capable servo supply.
• Six 60V+ / 100A+ N-channel MOSFETs.
• Low-side current shunts.
• A7105 2.4GHz RF transceiver with 16MHz crystal and antenna interface.
• Two 3-pin 2.54mm servo headers powered from the dedicated 6V servo buck.
• Heavy-duty plated-hole/post terminals for both battery input and motor phase outputs for waterproof minimal wiring.
• Low-profile SWD programming pads only; USB, CAN, and Hall/encoder connectors are intentionally removed for waterproofing.
• External waterproofable antenna interface using a low-risk U.FL/I-PEX-to-panel antenna path.

Diagram

• Preserve VESC-style STM32F405 + DRV8302 + 6 MOSFET architecture.
• MOSFETs must be rated at least 60V and >100A continuous.
• BATT+, GND, and motor phases require high-current copper pours suitable for 70A continuous, with exposed copper/solder-thickening or busbar option.
• Battery input BATT+ and BATT− shall use the same heavy-duty plated-hole/post concept as the motor phase outputs, using the 300-10021-02 Rev D post drawing unless later superseded by the user.
• Each motor phase output shall be a heavy-duty plated through-hole sized for mounting a 5mm gold-plated threaded post through the PCB.
• Motor and battery post holes require large annular rings, thermal/current-spreading copper, solder mask clearance, and mechanical keepouts suitable for hardware installation and waterproof sealing.
• User-supplied post drawing 300-10021-02 Rev D defines the high-current terminal hardware as brass, gold plated 0.8–1.2 µm, M5 × 0.8 thread, with Ø11 mm flat round mounting surface and Ø5.75 mm clearance-hole callout.
• For all five high-current posts (BATT+, BATT−, Phase A, Phase B, Phase C), PCB plated contact rings on both top and bottom shall match or slightly exceed the Ø11 mm flat mounting surface. Preferred board finish for these mating contact rings is gold plating/ENIG or other fab-approved gold finish for low contact resistance.

• A7105 connects directly to STM32F405 over SPI/3-wire SPI plus GIO1 interrupt/data-ready.
• RF section requires physical isolation from switching regulator and high-current MOSFETs.
• Solid unbroken RF ground plane and antenna keepout are required.

• Two 2.54mm 3-pin servo headers: Signal, 6V servo power, GND.
• Channel convention: Ch1 steering servo, Ch2 throttle to ESC bridge, Ch3 auxiliary servo.
• Dedicated onboard LiPo-input buck regulator provides a 6V servo rail sized for 5A peak-capable output.
• Add local decoupling/bulk capacitance, protection, and filtering on the servo rail to reduce brownout/noise risk.
• 100nF capacitor on the servo power line at each servo header.

• Low-profile SWD pads only: SWDIO, SWCLK, GND, 3.3V, and NRST if practical.
• No USB, CAN, or Hall/encoder connectors in the first integrated waterproof design.

• Include 4x non-plated M3 mounting holes for fastening the PCA inside the waterproof enclosure.
• Use approximately 3.2mm drill clearance unless final enclosure hardware requires adjustment.
• Maintain screw/standoff keepouts around each hole and avoid conflicts with RF keepout and high-current copper.

• Input: 3S-5S LiPo, approximately 9.9V depleted 3S to 21V full 5S.
• Motor current: 70A continuous design target.
• DRV8302 local 5V buck: preserve reference-support function, but do not rely on it as the high-current servo BEC.
• 6V servo rail: dedicated onboard buck from main LiPo, 5A peak-capable output target.
• 3.3V rail: generated from the quiet logic supply path for STM32F405 and A7105.

• Prefer LCSC/JLCPCB-available parts where possible.
• SMD production-intent design.
• High-current assembly may need solder-thickened copper or copper busbar reinforcement.
• Motor and battery post assembly uses the user-supplied 5mm gold-plated threaded posts installed through heavy-duty plated holes; preliminary footprint target is Ø5.75 mm finished hole with Ø11 mm or larger plated/gold-finished contact rings on both sides. Validate finished hole tolerance, plating capability, annular ring manufacturability, torque/mechanical retention, and sealing approach with the selected fabricator before release.
• Waterproofing implies minimal connectors and sealed pads/headers.
• External connectors are limited by design intent to battery input, three motor phase outputs, two servo headers, and the external antenna interface.
• Battery input terminals and motor phase terminals should share the same final post/hole hardware family if practical, subject to current rating, plating, torque, and enclosure sealing validation.

• STM32F405 runs VESC motor firmware plus AFHDS 2A receive/decode logic.
• A7105 SPI lines: SCK, SDIO, SCS, GIO1.
• Two hardware timer PWM outputs for steering and auxiliary servos.
• ADC input for preserved VESC battery voltage divider.
• Current sense ADC inputs from low-side shunts.
• SWD programming/debug through low-profile pads.
• Normal field communication/control should occur wirelessly through the AFHDS 2A receiver path; USB/CAN/Hall connectors are removed from the waterproof board.

• Heat-generating components must be on the bottom heat-sink side: six MOSFETs, DRV8302, shunts, power inductors.
• Opposite side reserved for STM32F405, A7105 RF, passive logic support, servo headers.
• Thermal vias and copper pour required under DRV8302 exposed pad and MOSFET drain pads.
• A7105 RF section and antenna must be far from power stage and switching nodes.
• Include 4x non-plated M3 mounting holes near board corners with keepouts for enclosure standoffs.
• Place three motor phase post holes plus BATT+ and BATT− post holes where enclosure sealing, cable access, high-current copper width, and mechanical wrench/clearance requirements can all be satisfied. Use Ø11 mm+ plated contact ring keepouts around each post.
• Place antenna interface to support a waterproof panel feedthrough/pigtail while keeping coax short and away from switching copper.

• Single STM32F405RGT6; no second receiver MCU.
• Add a dedicated onboard servo buck from the main LiPo for 6V, 5A peak-capable servo power.
• Preserve DRV8302 integrated buck function for reference-compatible local support; do not use it as the high-current servo rail.
• Preserve VESC battery voltage sensing divider and ADC connection.
• Preserve VESC-style power stage and current sensing topology.
• Remove USB, CAN, and Hall/encoder connectors for the waterproof integrated version; keep only low-profile SWD pads for programming/debug.
• Use external antenna rather than PCB trace antenna; source a waterproofable U.FL/I-PEX-to-panel antenna interface.
• Use heavy-duty plated motor phase holes for 5mm gold-plated threaded posts instead of ordinary motor solder pads.

• Initial schematic will be reconstructed from VESC 4.12 and public A7105 reference data because the uploaded ZIP currently fails upload processing.
• Exact LCSC MPN choices will be finalized after library availability checks.
• Antenna implementation will use an external antenna path; the low-risk connector/pigtail option is still being sourced.
• Servo buck part selection and thermal/current budget must be validated before schematic lock.
• Exact high-current post hardware dimensions are now based on user-supplied drawing 300-10021-02 Rev D: M5 × 0.8, Ø5.75 mm clearance-hole callout, Ø11 mm flat mounting surface, brass with 0.8–1.2 µm gold plating. Remaining layout-release checks: PCB fab ability to plate/gold-finish large annular rings, finished hole tolerance, allowable pad-to-edge clearances, torque/mechanical retention, and waterproof sealing method.

• Initial specification created from uploaded design brief on 2026-07-15.
• Updated with user-confirmed first-PCA decisions: M3 mounting holes, dedicated 6V/5A peak servo buck, low-profile SWD pads only, USB/CAN/Hall connector removal, and external waterproofable antenna interface.
• Added user requirement that each motor phase output use a heavy-duty plated through-hole for a 5mm gold-plated threaded post.
• Added user decision that BATT+ and BATT− should use the same plated-hole/post design concept as the motor phase terminals; user will provide high-current terminal details before layout lock.
• Extracted high-current post dimensions from user PDF 300-10021-02 Rev D and added layout/fabrication requirement for Ø11 mm+ gold-finished plated contact rings on both PCB sides around Ø5.75 mm finished holes.