4-Layer ARM Handheld PCB

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