Project Description: I'm building a compact, consumer-grade handheld device that hosts multiple ARM processors and modules on a single 4-layer board. The design must accommodate a high-speed USB hub, balanced power distribution, and impeccable signal integrity without exceeding the layer budget. Components to Integrate: Component Details Interface Luckfox Lyra Zero W ARM Cortex-A7 Linux SBC (65×30mm, 40-pin header) Direct solder or socket Teensy 4.1 ARM Cortex-M7 @600MHz audio DSP (61×18mm) 2.54mm headers SL2.1A USB Hub IC 4-port USB 2.0 hub Surface mount XIAO ESP32S3 LoRa module (21×18mm) 1.27mm headers STM32WB55 Module Dual-core ARM Cortex-M4/M0+ (Flipper brain) 8-pin header PyBoard v1.1 ARM Cortex-M4 backup controller 6-pin header GPS Module NEO-6M/8M 4-pin header CC1101 Module Sub-GHz radio 8-pin header ST25R3916 Module NFC/RFID 8-pin header OLED Displays (2x) 1.3" 128×64 I²C 4-pin headers Trackball Module BlackBerry-style USB HID 4-pin header Power Regulation 5V/3.3V from 10000mAh USB-C power bank + CR2032 coin cell (RTC backup) USB-C + through-hole External USB-C Ports (2x) Panel mount, power + data USB-C connectors PCB Specifications: Parameter Requirement Layers 4-layer (required for signal integrity) Dimensions ≤100mm × 70mm (fits custom titanium case) Thickness 1.6mm standard (or 1.0mm if possible) Mounting Holes 8× M2.5 (4 corners + 4 mid-edges) Impedance Control 90Ω differential for USB 2.0 traces Surface Finish ENIG (gold) for fine-pitch components Copper Weight 1 oz (standard) Critical Design Requirements: USB-C lines will run at high data rates - tight length matching, skew control, and via-transition optimization are critical Mixed-signal design - separate analog (Teensy audio) and digital grounds Thermal management - all components in enclosed titanium case; include thermal vias and copper pours Power distribution - multiple voltage domains (5V, 3.3V, coin cell) with proper decoupling JLCPCB assembly ready - must comply with their DFM rules and component library Test points - include for critical signals (power, USB, I²C) for debugging What I Already Have: Preliminary component list and block diagram Rough mechanical envelope (167×97×20mm titanium case) Understanding of functional requirements What I Need From You: Complete board implementation - stack-up definition, impedance-controlled routing, differential pair tuning, power/ground split planning Apply SI and PI best practices - pre-layout simulations where needed, post-route checks JLCPCB assembly optimization - component selection for availability, DFM compliance Final outputs ready for manufacturing and assembly Deliverables (Full Ownership Required): Deliverable Format Schematic PDF + source (Altium preferred, KiCad/OrCAD acceptable) PCB Layout Native format + Gerber (RS-274X), drill, IPC-356 netlist Stack-up Drawing PDF with impedance control notes Bill of Materials (BOM) Excel/CSV with LCSC/JLCPCB part numbers Component Placement List (CPL) CSV with centroid data 3D STEP File STEP format for case fit verification Design Report PDF summarizing impedance targets, simulation results, critical layout decisions Assembly Drawing PDF with component locations and notes Legal & Ownership: Full IP ownership is required. I will use Upwork's IP Agreement Upgrade to formalize this. All work product becomes my exclusive property upon final payment. Experience Required: Skill Priority 4+ layer PCB design (Altium/KiCad) ⭐⭐⭐⭐⭐ High-speed USB layout (90Ω impedance) ⭐⭐⭐⭐⭐ Multi-processor ARM systems ⭐⭐⭐⭐⭐ Mixed-signal design (digital + analog) ⭐⭐⭐⭐ JLCPCB assembly experience ⭐⭐⭐⭐ Power distribution design ⭐⭐⭐⭐ Signal integrity analysis ⭐⭐⭐ Budget & Timeline: Item Details Budget $300 USD (fixed price or hourly at $35-55/hr) Timeline 2-3 weeks Milestones Schematic (25%), Layout (50%), Final Files (25%) Questions for Applicants: Have you designed boards with USB hubs (SL2.1A or similar) before? What's your experience with 4-layer ARM-based multi-processor designs? Can you share examples of similar projects? Have you prepared designs for JLCPCB assembly? Are you comfortable with the IP ownership requirements? I'm aiming for a board that passes first-article testing without costly respins, so clear documentation and transparent reasoning behind key choices are essential. If this aligns with your high-speed PCB expertise, let's bring this handheld to life! ✅ KEY IMPROVEMENTS MADE Original Enhanced Generic "multiple ARM processors" Specific components listed Vague USB hub SL2.1A IC named No assembly target JLCPCB specified Generic deliverables Complete list with formats No legal mention IP ownership clause No interview questions Screening questions