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USB Hub+

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USB 2.0 High-Speed Hub is a **professional development hub** with integrated programming tools and peripherals. It combines a 7-port USB 2.0 hub with ST-Link programmer, dual UART bridges, and SD card reader into a single compact device for embedded development workflows.

Features

Main Hub Architecture

  • Primary Hub: FE2.1 USB 2.0 Hub IC (7 downstream ports)
  • Secondary Hub: FE1.1S USB 2.0 Hub IC (4 downstream ports, cascaded)
  • Total Ports: 11 USB endpoints (6 external + 4 internal peripherals + 1 upstream)
  • External Connectors:
  • 3× USB-C downstream ports (Ports 5, 6, 7)
  • 3× USB-A downstream ports (Ports 2, 3, 4)
  • 1× USB-C upstream port (host connection)
  • 1× USB-C power input (5V 3A)

Integrated Development Tools

  • ST-Link V2 Programmer: STM32F103C8T6-based in-circuit debugger
  • SWD interface (SWCLK, SWDIO, SWO)
  • Compatible with STM32, STM8 targets
  • Onboard programming via 5-pin header
  • Status LED indicator
  • Dual UART Bridges: 2× CH343P USB-to-Serial converters
  • Selectable 3.3V / 5V logic levels (via toggle switches)
  • Hardware flow control (RTS/CTS)
  • 6-pin headers (GND, VCC, TX, RX, RTS, DTR)
  • Individual activity LEDs
  • SD Card Reader: GL823K-based MicroSD card interface
  • Push-pull card slot
  • Hot-swap capable
  • USB 2.0 High-Speed transfer

Power Management

  • Individual Port Protection: TPS2051BDBVR load switches (500mA per port)
  • Overcurrent protection
  • Thermal shutdown
  • Inrush current limiting
  • Enable control via hub IC
  • USB-C Power Delivery:
  • Downstream ports: 56kΩ CC resistors (advertises 500mA)
  • Upstream port: 5.1kΩ CC resistors (UFP/sink configuration)
  • Voltage Regulation:
  • AMS1117-3.3 LDO for 3.3V peripherals
  • Separate power domains for hub ICs (3.3V, 1.8V)

Protection Circuitry

  • ESD Protection: TPD4E001 TVS diode arrays on all USB ports
  • ±8kV contact discharge protection
  • Clamping voltage: 17V
  • Protects D+, D-, CC1, CC2 lines
  • Port Activity LEDs: 6× green indicator LEDs (1 per external port)

Hardware

PCB Specifications

  • Layers: 4-layer stackup
  • L1: High-speed signals, components (1oz copper)
  • L2: Solid ground plane (1/2oz copper, 0.0994mm prepreg)
  • L3: Ground + power pours (1/2oz copper)
  • L4: Power distribution, decoupling (1oz copper)
  • Impedance Control:
  • USB differential pairs: 90Ω ±10% (0.165mm trace, 0.2mm gap)
  • USB-C CC lines: 50Ω single-ended
  • Dimensions: ~100mm × 70mm
  • Mounting: 4× M2.5 mounting holes

Schematics / PCB / 3D

Port Mapping

External Ports (User-Accessible)

Port                Connector       Hub IC        Downstream # Features
------ ----------- -------- -------------- ---------------------------------
PORT 2 USB-A FE2.1         DS2 500mA protected, activity LED
PORT 3 USB-A FE2.1         DS3 500mA protected, activity LED
PORT 4 USB-A FE2.1         DS4 500mA protected, activity LED
PORT 5 USB-C FE2.1         DS5 500mA protected, activity LED
PORT 6 USB-C FE2.1         DS6 500mA protected, activity LED
PORT 7 USB-C FE2.1         DS7 500mA protected, activity LED

Internal Peripherals (Soldered)

Peripheral                Hub IC      Downstream #      Interface
------------ -------- -------------- --------------------------------------------
ST-Link ISP FE1.1S         DS11 5-pin header (GND, RST, SWO, CLK, DIO)
UART Bridge 1 FE1.1S         DS10 6-pin header + 3.3V/5V switch
UART Bridge 2 FE1.1S         DS9 6-pin header + 3.3V/5V switch
SD Card Reader FE1.1S         DS8 Push-pull MicroSD slot

Technical Specifications

USB Hub Controllers

FE2.1 (Primary Hub) - Package: LQFP-48 - Downstream ports: 7 - Overcurrent detection: Grouped (OVCJ1, OVCJ5) - Crystal: 12MHz - Power: 3.3V (digital), 1.8V (analog), 5V (VBUS)

FE1.1S (Secondary Hub) - Package: BQFN-24 - Downstream ports: 4 - Cascade connection to FE2.1 port 1 - Crystal: 12MHz - Power: 3.3V, 5V (VBUS)

Load Switches (TPS2051BDBVR)

  • Input voltage: 2.7V - 5.5V
  • Current limit: 500mA (hardware)
  • Rds(on): 95mΩ typical
  • Features: OVCP, OTP, UVLO
  • Package: SOT-23-5

UART Bridges (CH343P)

  • Package: TQFN-16
  • Data rates: up to 6Mbps
  • Logic levels: 1.8V - 5.5V (selectable via VIO)
  • Pins: TX, RX, RTS, CTS, DTR, DSR, DCD, RI
  • Crystal: 12MHz
  • Package: LQFP-48
  • Flash: 64KB
  • RAM: 20KB
  • Crystal: 8MHz

SD Card Reader (GL823K)

  • Interface: USB 2.0 High-Speed
  • Card support: SD, SDHC, SDXC (MicroSD format)
  • Hot-swap: Yes
  • Power: 3.3V + 5V (card power selectable)

Usage

Basic Operation

  1. Power Connection:
  2. Connect 5V 3A power supply to power USB-C connector

  3. Alternative: Power via upstream USB-C (limited to USB spec current)

  4. Host Connection:

  5. Connect upstream USB-C port to computer
  6. Hub enumerates as USB 2.0 High-Speed device

  7. All ports become available

  8. UART Bridge Configuration:

  9. Toggle S1/S2 switches to select 3.3V or 5V logic levels
  10. Connect target via 6-pin headers

  11. Bridges enumerate as CH343 serial ports

  12. ST-Link Programming:

  13. Connect target via 5-pin SWD header (or dedicated STLINK_ISP header)
  14. Use STM32CubeIDE, Keil, or OpenOCD
  15. Status LED indicates connection

UART Pinouts

PIN 1: GND
PIN 2: RTS (output from bridge)
PIN 3: 5V or 3.3V (selectable via switch)
PIN 4: TX (output from bridge)
PIN 5: 3.3V (always)
PIN 6: RX (input to bridge)

PIN 1: VCC (3.3V output to target)
PIN 2: SWCLK
PIN 3: GND
PIN 4: SWDIO
PIN 5: NRST (reset)
PIN 6: SWO (optional, for SWV trace)

Onboard Programming Header (6-pin, 1.27mm pitch)

PIN 1: VCC (3.3V)
PIN 2: SWCLK
PIN 3: GND
PIN 4: SWDIO
PIN 5: NRST
PIN 6: SWO

Important Design Notes

USB-C CC Resistor Configuration

  • Downstream ports (host): 56kΩ pull-ups to VBUS
  • Advertises default USB power (500mA)
  • Upstream port (device): 5.1kΩ pull-downs to GND
  • Configures as UFP (sink/device role)

STM32F103 USB Pull-up

The STM32F103C8T6 requires an external 1.5kΩ pull-up resistor on D+ (PA12) to 3.3V. This is different from newer STM32 families (F4, G4, etc.) which have internal pull-ups.

In schematic: R39 = 1.5kΩ from PA12 to +3V3 ✓

Crystal Load Capacitors

All crystals use 10pF load capacitors (C0G/NP0 type): - Formula: C_load = 2 × (CL - C_stray) - C_stray ≈ 5pF (LQFP package + PCB traces) - Therefore: C_load = 2 × (10pF - 5pF) = 10pF

Critical: Verify all crystals are specified for CL = 10pF (especially the 8MHz for STM32).

Power Sequencing

  1. 5V input powers load switches and hub VBUS pins
  2. AMS1117-3.3 generates 3.3V for logic
  3. Hub ICs generate internal 1.8V for analog/PLL
  4. All power rails must be stable before USB enumeration

High-Speed USB Routing

  • Differential pairs: 90Ω impedance, length matched ±2mm
  • Trace geometry: 0.165mm width, 0.2mm gap
  • Reference plane: Solid GND on L2 (0.0994mm away)
  • Via fencing around connectors for EMI suppression
  • TVS diodes placed <3mm from connectors

Manufacturing

PCB Fabrication Specs

Layers:           4
Board thickness:  1.6mm
Copper weight:    1oz outer, 1/2oz inner
Min trace/space:  6/6 mil (0.15/0.15mm)
Min hole size:    0.3mm
Surface finish:   ENIG (recommended) or HASL
Impedance:        Controlled (90Ω diff, 50Ω SE)
Solder mask:      Green (or choice)
Silkscreen:       White both sides

Resources

Datasheets

Tools

  • PCB Design: Altium Designer
  • Programming: STM32CubeIDE, OpenOCD, st-link tools
  • Serial Terminal: PuTTY, TeraTerm, minicom

Photos