SmartUSBHub Pro 4CH USB2.0 User Guide

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This document applies to: SmartUSBHub Pro 4CH USB2.0

Last updated on: June 4, 2026

Overview

The SmartUSBHub is a 4-port, software-programmable USB 2.0 (480 Mbps) hub that offers per-port power and data control, as well as voltage and current sensing. It is designed for development, testing, and device management applications.

  1. Per-Port USB Power & Data Control

    • Individually enable or disable power and data lines on any downstream port

    • Simulates manual hot-plug behavior via button or command/software

  2. Voltage and Current Monitoring

    • Each port supports real-time voltage and current measurement for power analysis and device diagnostics

  3. Software-Controllable & Multi-Platform Compatible

    • USB CDC-based serial command interface, provide Python libraries and software for easy integration

    • Supports on Windows, macOS, Linux; no additional drivers required

  4. Multiple Operating Modes

    • Normal Mode: all ports operate independently

    • Interlock Mode: only one port is active at any time

    • Each downstream port supports customizable power-on defaults and power-loss state recover

  5. Topology Support for Scalable Deployment

    • Each hub can be assigned a unique address for large-scale, multi-hub configurations

Trusted by Industry Leaders

From consumer electronics to autonomous driving, from global smartphone leaders to high-performance chip design companies, SmartUSBHub is widely deployed in the R&D, automated testing, and production validation flows of top-tier enterprises.

SmartUSBHub is now used by 20+ global industry leaders, Representative use cases include:

  • Automotive Industry: Used by over 3 of the global top 5 Tier 1 suppliers.

  • Smartphone: Used by over 3 of the top 5 global smartphone OEMs.

  • Semiconductors & Chip Design: Deployed by over 5 leading chip design companies worldwide.

  • AI & Large Model Platforms: Integrated into internal testing flows of at least 2 global AI tech giants.

  • Telecom & IoT Equipment: Adopted at scale by multiple leading global and regional vendors.

Application Scenarios

Embedded System Debugging

  • Precise USB Enumeration Control: Scripted USB port toggling allows for predefined enumeration sequences, ensuring key devices are recognized first in multi-device systems, enhancing repeatability in testing and predictability in boot processes.

  • Remote Debugging & Reset: Engineers frequently unplug and replug debug tools (e.g., J-Link) or USB devices to reset embedded targets. SmartUSBHub enables remote control of USB power and data, simulating plug/unplug events to reboot hung devices or trigger bootloader modes—particularly useful in unattended lab setups.

  • Power Monitoring & Fault Diagnosis: Real-time voltage and current monitoring helps detect issues such as sudden power loss or abnormal current draw. Engineers can identify hardware faults early by correlating power anomalies with test failures.

Automated Validation Testing

  • Reliability Testing: SmartUSBHub can repeatedly toggle power and data lines to simulate plug/unplug and power loss scenarios, validating USB port resilience and firmware stability under stress (e.g., interrupted flash writes). No physical intervention is needed.

  • Power Profiling: Real-time logging of per-port voltage and current during automated test cases enables correlation with device behavior. Engineers can validate power consumption during standby and active modes, spotting overdraw or leakage issues.

  • Test System Integration: The Python API and serial command interface allow seamless integration into ATEs. Engineers can perform parallel or sequential control over multiple USB devices for batch reboots or firmware updates, improving test coverage and throughput.

Production Line Testing

  • Boost Production Throughput: SmartUSBHub allows multiple DUTs to be tested simultaneously via software-controlled port toggling, eliminating the need for manual reconnection and increasing testing speed and efficiency.

  • Automated Firmware Flash & Reboot: Automated workflows can use SmartUSBHub to sequentially toggle USB data lines for firmware flashing, then power-cycle each device remotely. This reduces manual errors and ensures consistent execution across batches.

  • Electrical Parameter Checks: Per-port current monitoring enables the system to flag short circuits or overcurrent conditions, helping to isolate defective units in real-time.

USB Asset Management

  • Secure Peripheral Authorization: Control connections to sensitive devices like dongles, e-signature tokens, and tax UKeys, enabling physical-layer enable/disable logic for security-critical scenarios.

  • Peripheral Switching in Shared Environments: Manage USB peripherals like cameras, microphones, and KVMs in meeting rooms or data centers from a central controller.

  • Hardware-Level Isolation & Auditability: Ideal for finance and government sectors where physical USB disconnection is required for compliance or data security. Enables physical-layer access control and USB event traceability.

Device Overview

device_overview_en

Connection Guide

connection_guide

Device Interfaces

  • Command Port (×1): Used for sending/receiving control commands (connects to host).

  • Auxiliary Power Port (×1): Connect an external power supply to this port when downstream devices require higher power.

  • USB Upstream Port (×1): Port for connecting to a USB host.

  • USB Downstream Ports (×4): Ports for connecting USB devices.

接线图

[1] Button(s):

Single click: Toggle the corresponding channel on/off.

Long press:

  • [Button 1] For 3 seconds: Switch operating mode (Normal/Interlock).

  • [Button 1] For 6 seconds: Restore factory settings.

  • [Button 2] For 3 seconds: Enable/disable power-loss state Persistence feature.

[2] Channel Indicator LEDs:

On: Channel is ON.

Off: Channel is OFF.

[3] Status Indicator LED:

Slow flash: Normal mode.

Fast flash: Interlock mode.

[4] Auxiliary Power Port:

If the downstream device’s power draw exceeds 10 W (5 V 2 A), connect an external power supply to this port.

Recommended max input: 30 W (5 V 6 A), no over-current protection.

[5] Device Communication Port:

Used for control commands (connects to host).

Max input: 20 W (5 V 4 A), with reverse-protection, over-voltage protection, and over-current protection.

[6] USB 2.0 Upstream Port:

Provides power and data connection to a USB host (e.g., PC).

Max input: 20 W (5 V 4 A), with reverse feed protection, over-voltage protection, and over-current protection.

[7] USB 2.0 Downstream Ports:

USB Type-A ports with power and data, used for connecting USB devices.

Max output per port: 20 W (5 V 4 A).

[!NOTE]

Connect USB 2.0 Upstream Port [6] to the host for data transfer, and connect Device Communication Port [5] for command control.

In other words, if you need both data transfer and command control, connect both of these ports to the same host.

[!WARNING]

This device only supports 5V DC input. Exceeding this voltage may result in damage.

Avoid operating beyond the rated power; excessive load may cause overheating of cables or connectors and lead to device failure.

System Compatibility

This device uses a standard USB CDC interface and requires no driver. Just plug and play. It has been verified on the following systems:

  • Windows 10, 11 or newer

  • macOS 10.9 or newer

  • Linux distributions (e.g., Ubuntu)

  • Other x86, AMD64, ARM64 platforms (e.g., Apple Silicon, Windows on ARM)

[!NOTE]

For Windows 7 and earlier versions of Windows, driver needs to be patched. See this guide for more information CDC Driver patch

USB Compatibility

This device complies with the USB 2.0 specification. The upstream port supports USB 2.0 High-Speed and Full-Speed. The downstream ports support USB 2.0 High-Speed (480 Mbps), Full-Speed (12 Mbps), and Low-Speed (1.5 Mbps), and are backward compatible with USB 1.1.

Supports high-performance MTT mode (4 transaction translators, one per port, for concurrent processing), giving each port an independent transaction translator and achieving full-bandwidth parallel transfers—total bandwidth is four times that of STT mode.

Compatible with all USB devices (no picky device compatibility).

Common Devices

connect_device

Verified Devices

Name

keyboard

Keyboard, mouse and other input devices

thumbdrive

USB flash drive

harddrive

External hard drive

dongle

CA certificate dongle, digital signature device

iPhone

iPhone

iPad

iPad

s25

Other smartphones, tablets

cam

USB webcam / microphone / audio interface

printer

Various USB CDC devices (e.g., industrial, printer)

Devices Requiring USB Power

SmartUSB hub supports any powered device with current consumption under 4 A.

Verified Devices

Name

fan

USB fan

pump

Water pump

screenbar

Xiaomi monitor light, BenQ ScreenBar series

led

USB LED strip

speaker

USB speaker

Development Tools

Verified Devices

Name

jlink

Segger J-Link

stlink

ST-Link

xds110

XDS-110

xds100

XDS-100

daplink

DAP-LINK

canbox

USB-to-CAN adapter

logic_analyzer

Logic analyzer

usbserial

USB serial bridge

dongle

USB dongle (hardware key)

esp32

Various development boards and prototypes

raspberry

Raspberry Pi

instrument

Instruments with USB interface

[!WARNING]

Does not support fast-charging protocols; when a phone or tablet is connected, the charging current will be the same as if it were connected directly to a computer.

Device Specifications

Dimensions

10.6 × 4.6 × 1.8 cm (L × W × H)

Electrical Specifications

  • Input Voltage: DC 5 V

  • Max Input Current: 16 A

  • Max Output Current: 4 A per channel

  • Control Methods: Button control, Command control

  • Power Supply: Bus-powered from host or via auxiliary power port

Interfaces

  • Control Interface: USB (non-TTL signal, internally converted to USB serial)

  • Upstream Interface: 1 × USB-C port

  • Downstream Interface: 4 × USB-A ports

  • Auxiliary Power Interface: 1 × USB-C port

Protection Features

  • Over-Current Protection: Upstream, communication, and each downstream port have a self-resetting 4 A fuse; auxiliary power port has no OCP fuse.

  • Over-Voltage Protection: Upstream and communication ports have over-voltage protection.

  • Reverse Current Protection: Upstream, communication, and auxiliary power ports have reverse current (backfeed) protection; downstream ports have no backfeed protection.

  • ESD Protection: Critical interfaces are protected with ESD components.

Device Block Diagram

image-20250614180531459

Indicator Lights

There is an indicator LED on the far left of the device.

sc2

Indicator patterns:

Blink Pattern

Meaning

0.5 s on, 0.5 s off

Normal operating mode

0.25 s on, 0.25 s off

Channel interlock mode

Momentary off flash (overlaid)

Receiving a control command frame

Buttons

The device has 4 buttons corresponding to the 4 USB-A channels. The following special functions are available:

Operation

Function

Default

Button 1 (hold while powering on)

Enter firmware upgrade mode

Button 1 (long press > 6 s)

Restore factory settings

Button 1 (long press > 3 s)

Toggle operating mode (Normal/Interlock, persists after power cycle)

Normal Mode

Button 2 (long press > 3 s)

Enable/Disable power-loss state Persistence (remember channel state)

Disabled

Command Set

The device uses a simple request-response communication protocol for control. The available commands are:

Function

CMD

Description

Control channel power

0x01

Control the VBUS power state of a specified channel

Query channel power state

0x00

Query whether a channel’s VBUS power is on

Control power in interlock mode

0x02

In interlock mode, only allow one channel on at a time

Query voltage

0x03

Query the channel’s VBUS voltage (unit: mV)

Query current

0x04

Query the channel’s current (unit: mA)

Control USB data lines

0x05

Control whether D+/D− are connected

Query USB data line status

0x08

Query the current on/off status of D+/D−

Set button control permission

0x09

Enable or disable the physical button control

Query button control permission

0x0A

Query whether button control is enabled

Set power default state

0x0B

Configure the default on/off state of VBUS after power-up

Query power default state

0x0C

Query the channel’s power default state

Set data default state

0x0D

Configure the default on/off state of D+/D− after power-up

Query data default state

0x0E

Query the default state of D+/D−

Set power-loss state Persistence

0x0F

Enable/disable remembering channel state on power loss

Query power-loss Persistence state

0x10

Query if power-loss state Persistence is enabled

Set Device Address

0x11

Set the device address, used to identify and distinguish hubs in multi-hub setups

Get Device Address

0x12

Get the device address, used to identify and distinguish hubs in multi-hub setups

Set operation mode

0x06

Switch Normal/Interlock mode

Query operation mode

0x07

Query the current operating mode

Restore factory settings

0xFC

Restore factory settings

Query firmware version

0xFD

Query the device firmware version

Query hardware version

0xFE

Query the current hardware version

Frame format

The protocol frame format for control, query, interlock, and set commands is:

Header1

Header2

CMD

Channel No.

Channel Value

Additional Value

SUM8 Checksum

0x55

0x5A

[0x01 0x02 0x03]

[0x01 0x02 0x04 0x08]

[0x00 0x01]

Present only if command has data

CMD + CH + data

The protocol frame format for reading channel voltage or current is:

Header1

Header2

CMD

Channel No.

Value [15:8] (MSB)

Value [7:0] (LSB)

SUM8 Checksum

0x55

0x5A

[0x01 0x02 0x03]

[0x01 0x02 0x04 0x08]

MSB

LSB

CMD+CH+VAL

Header1

Header2

CMD

DATA[1-3]

SUM8 校验和

0x55

0x5A

Refer to the command set

depends on the specific command

CMD+CH+data[1-3]

Command Examples

[!NOTE]

  • All data values below are in hexadecimal.

  • Channel values use the Channel_e enum, not the channel number. In control and query commands, bitwise OR can be used for batch control and query; if the device is in interlock mode, only the interlock control command [0x02] can be used for control; bitwise combination is ineffective.

  • Frames with an incorrect format or unsupported commands will not receive a response.

  • When a button is pressed, a status report [0x00] command of that channel’s current state will be sent.

  • The provided package includes a UART assistant tool (uart_tool) for quick start.

  • A Python control library smartusbhub is available.

  • In this document, USB downstream port is referred to simply as a channel.

Channel Enum Values (Channel_e):

typedef enum
{
    CH1 = 0x01,
    CH2 = 0x02,
    CH3 = 0x04,
    CH4 = 0x08, 
}Channel_e;

[!NOTE]

Device Communication Parameters:

  • Baud Rate: 115200 – 921600 (Default: 115200)

  • Data Bits: 8

  • Parity: None

  • Stop Bits: 1

Device Name:

  • Windows: COMx

  • Linux: /dev/ttyACMx

  • macOS: /dev/cu.usbmodemx

Control Channel Power Switch (CMD: 0x01)

[!NOTE]

If the device is in interlock mode, the normal control command (CMD: 0x01) is ineffective; you must use the interlock control command (CMD: 0x02) instead.

If a control command is sent in interlock mode, an “invalid command” frame will be returned:

Invalid Command:

55 5A 01 FF FF FF

Data Field Description:

data[0]

data[1]

Channel ID

Channel Power State

Channel_e

0 (OFF), 1 (ON)

Turn On Channel 1 Power

Command:

55 5A 01 01 01 03

Response:

55 5A 01 01 01 03

Turn Off Channel 1 Power

Command:

55 5A 01 01 00 02

Response:

55 5A 01 01 00 02

Turn On Channel 2 Power

Command:

55 5A 01 02 01 04

Response:

55 5A 01 02 01 04

Turn Off Channel 2 Power

Command:

55 5A 01 02 00 03

Response:

55 5A 01 02 00 03

Turn On Channel 3 Power

Command:

55 5A 01 04 01 06

Response:

55 5A 01 04 01 06

Turn Off Channel 3 Power

Command:

55 5A 01 04 00 05

Response:

55 5A 01 04 00 05

Turn On Channel 4 Power

Command:

55 5A 01 08 01 0A

Response:

55 5A 01 08 01 0A

Turn Off Channel 4 Power

Command:

55 5A 01 08 00 09

Response:

55 5A 01 08 00 09

Combined Control Example

Turn On Channel 1 and Channel 3 Power

Command:

55 5A 01 05 01 07

Response:

55 5A 01 05 01 07
Turn Off Channel 1 and Channel 3 Power

Command:

55 5A 01 05 00 06

Response:

55 5A 01 05 00 06
Turn On All Channels

Command:

55 5A 01 0F 01 11

Response:

55 5A 01 0F 01 11
Turn Off All Channels

Command:

55 5A 01 0F 00 10

Response:

55 5A 01 0F 00 10

Query Channel Power State (CMD: 0x00)

Data Field Description:

data[0]

data[1]

Channel ID

Channel Power State

Channel_e

0 (OFF), 1 (ON)

Query Channel 1 Power State

Command:

55 5A 00 01 00 01

Response:

If channel 1 power is OFF:

55 5A 00 01 00 01

If channel 1 power is ON:

55 5A 00 01 01 02

Query Channel 2 Power State

Command:

55 5A 00 02 00 02

Response:

If channel 2 power is OFF:

55 5A 00 02 00 02

If channel 2 power is ON:

55 5A 00 02 01 03

Query Channel 3 Power State

Command:

55 5A 00 04 00 04

Response:

If channel 3 power is OFF:

55 5A 00 04 00 04

If channel 3 power is ON:

55 5A 00 04 01 05

Query Channel 4 Power State

Command:

55 5A 00 08 00 08

Response:

If channel 4 power is OFF:

55 5A 00 08 00 08

If channel 4 power is ON:

55 5A 00 08 01 09

Combined Control Example:

Query All Channels’ Power States

Command:

55 5A 00 0F 00 0F

Response:

55 5A 00 01 01 02 
55 5A 00 02 00 02 
55 5A 00 04 00 04 
55 5A 00 08 01 09

  • Channel 1 Power: ON

  • Channel 2 Power: OFF

  • Channel 3 Power: OFF

  • Channel 4 Power: ON

Control Channel USB Data Line Switch (CMD: 0x05)

The device can control the connectivity of the D+ and D− differential pair for a specified channel, allowing scenarios where power is maintained but data is disconnected.

[!NOTE]

  • By default, each channel’s USB data (D+/D−) lines are connected unless the user sends a control command (CMD: 0x05) to manually disconnect them.

  • If power-loss state Persistence is enabled, the data line on/off state will be remembered.

Data Field Description:

data[0]

data[1]

Channel ID

Channel Data Line State

Channel_e

0 (OFF), 1 (ON)

Connect Channel 1 Data Lines

Command:

55 5A 05 01 01 07

Response:

55 5A 05 01 01 07

Disconnect Channel 1 Data Lines

Command:

55 5A 05 01 00 06

Response:

55 5A 05 01 00 06

Connect Channel 2 Data Lines

Command:

55 5A 05 02 01 08

Response:

55 5A 05 02 01 08

Disconnect Channel 2 Data Lines

Command:

55 5A 05 02 00 07

Response:

55 5A 05 02 00 07

Connect Channel 3 Data Lines

Command:

55 5A 05 04 01 0A

Response:

55 5A 05 04 01 0A

Disconnect Channel 3 Data Lines

Command:

55 5A 05 04 00 09

Response:

55 5A 05 04 00 09

Connect Channel 4 Data Lines

Command:

55 5A 05 08 01 0E

Response:

55 5A 05 08 01 0E

Disconnect Channel 4 Data Lines

Command:

55 5A 05 08 00 0D

Response:

55 5A 05 08 00 0D

Combined Control Example:

Connect Data Lines on All Channels

Command:

55 5A 05 0F 01 15

Response:

55 5A 05 0F 01 15
Disconnect Data Lines on All Channels

Command:

55 5A 05 0F 00 14

Response:

55 5A 05 0F 00 14

Query Channel USB Data Line State (CMD: 0x08)

Data Field Description:

data[0]

data[1]

Channel ID

Channel Data Line State

Channel_e

0 (OFF), 1 (ON)

Query Channel 1 Data Line State

Command:

55 5A 08 01 00 09

Response:

If channel 1 data is DISCONNECTED:

55 5A 08 01 00 09

If channel 1 data is CONNECTED:

55 5A 08 01 01 0A

Query Channel 2 Data Line State

Command:

55 5A 08 02 00 0A

Response:

If channel 2 data is DISCONNECTED:

55 5A 08 02 00 0A

If channel 2 data is CONNECTED:

55 5A 08 02 01 0B

Query Channel 3 Data Line State

Command:

55 5A 08 04 00 0C

Response:

If channel 3 data is DISCONNECTED:

55 5A 08 04 00 0C

If channel 3 data is CONNECTED:

55 5A 08 04 01 0D

Query Channel 4 Data Line State

Command:

55 5A 08 08 00 10

Response:

If channel 4 data is DISCONNECTED:

55 5A 08 08 00 10

If channel 4 data is CONNECTED:

55 5A 08 08 01 11

Combined Control Example:

Combined Control Example: Query All Channels’ Data Line States

Command:

55 5A 08 0F 00 17

Response:

55 5A 08 01 01 0A
55 5A 08 02 01 0B
55 5A 08 04 01 0D
55 5A 08 08 01 11

  • Channel 1 Data: CONNECTED

  • Channel 2 Data: CONNECTED

  • Channel 3 Data: CONNECTED

  • Channel 4 Data: CONNECTED

Control Power in Interlock Mode (CMD: 0x02)

Control Truth Table:

Channel 1

Channel 2

Channel 3

Channel 4

Closed

Closed

Closed

Closed

Open

Closed

Closed

Closed

Closed

Open

Closed

Closed

Closed

Closed

Open

Closed

Closed

Closed

Closed

Open

Data Field Description:

data[0]

data[1]

Channel ID

Channel Power State

Channel_e

0 (OFF), 1 (ON)

Turn On Channel 1 Power (others off)

Command:

55 5A 02 01 01 04

Response:

55 5A 02 01 01 04

Turn On Channel 2 Power (others off)

Command:

55 5A 02 02 01 05

Response:

55 5A 02 02 01 05

Turn On Channel 3 Power (others off)

Command:

55 5A 02 04 01 07

Response:

55 5A 02 04 01 07

Turn On Channel 4 Power (others off)

Command:

55 5A 02 08 01 0B

Response:

55 5A 02 08 01 0B

Turn Off All Channels

Command:

55 5A 02 0F 01 12

Response:

55 5A 02 0F 01 12

Query Channel Voltage (CMD: 0x03)

[!NOTE]

  • The device can measure the output voltage (VBUS) of each channel, which can be used to check if the bus is functioning normally.

  • The voltage unit is mV (millivolts).

  • Voltage resolution is 0.1 V

Data Field Description:

data[0]

data[1]

data[2]

Channel ID

Channel Voltage value[15:8]

Channel Voltage value[7:0]

Channel_e

-

-

Query Channel 1 Voltage:

Command:

55 5A 03 01 00 04

Response:

55 5A 03 01 13 56 6D

Channel 1 Voltage = 0x1356 = 4950 mV (channel ON)

Query Channel 2 Voltage:

Command:

55 5A 03 02 00 05

Response:

55 5A 03 02 00 0C 11

Channel 2 Voltage = 0x000C = 12 mV (channel OFF)

Query Channel 3 Voltage:

Command:

55 5A 03 04 00 07

Response:

55 5A 03 04 00 09 10

Channel 3 Voltage = 0x0009 = 9 mV (channel OFF)

Query Channel 4 Voltage:

Command:

55 5A 03 08 00 0B

Response:

55 5A 03 08 00 08 13

Channel 4 Voltage = 0x0008 = 8 mV (channel OFF)

Query Channel Current (CMD: 0x04)

[!NOTE]

  • The device can measure the current of each channel, which can be used to assess the device’s operating status.

  • The current unit is mA (milliamps).

  • Current resolution is 0.1 A

Data Field Description:

data[0]

data[1]

data[2]

Channel ID

Channel Current value [15:8]

Channel Current value [7:0]

Channel_e

-

-

Query Channel 1 Current:

Command:

55 5A 04 01 00 05

Response:

55 5A 04 01 01 29 2F

Channel 1 Current = 0x0129 = 297 mA

Query Channel 2 Current:

Command:

55 5A 04 02 00 06

Response:

55 5A 04 02 00 00 06

Channel 2 Current = 0x0000 = 0 mA

Query Channel 3 Current:

Command:

55 5A 04 04 00 08

Response:

55 5A 04 04 00 00 08

Channel 3 Current = 0x0000 = 0 mA

Query Channel 4 Current:

Command:

55 5A 04 08 00 0C

Response:

55 5A 04 08 00 00 0C

Channel 4 Current = 0x0000 = 0ma

Set Button Control Permission (CMD: 0x09)

[!NOTE]

  • By default, the device allows channel control via the buttons.

  • This setting applies to all buttons and channels.

  • Long-press button functions are not affected.

  • This setting is retained after power off.

Data Field Description:

data[0]

data[1]

Fixed

Enable Button Control

0x00

0 (false), 1 (true)

Disable Control via Buttons

Command:

55 5A 09 00 00 09

Response:

55 5A 09 00 00 09

Enable Control via Buttons

Command:

55 5A 09 00 01 0A

Response:

55 5A 09 00 01 0A

Query Button Control Permission (CMD: 0x0A)

Command:

55 5A 0A 00 00 0A

Response:

Button control enabled:

55 5A 0A 00 01 0B

Button control disabled:

55 5A 0A 00 00 0A

Set Channel Power Default State (CMD: 0x0B)

[!NOTE]

  • When determining channel states after power-up, the default state has higher priority than the power-loss Persistence feature. If the default state feature is enabled, even if the power-loss Persistence feature is also enabled, the system on power-up will still use the default state to decide each channel’s power or data on/off status.

  • When the default state feature is disabled, the channels’ power-on state will be decided by the power-loss Persistence setting. If power-loss Persistence is also disabled (default configuration), then upon power-up all channels will default to OFF.

  • Factory default configuration: all channel power outputs are OFF.

Data Field Description:

data[0]

data[1]

data[2]

Channel ID

Enable Default Power State

Default Power Value

Channel_e

0 (false), 1 (true)

0 (OFF), 1 (ON)

Set Channel 1 Power Default to ON

Command:

55 5A 0B 01 01 01 0E

Response:

55 5A 0B 01 01 01 0E

Set Channel 1 Power Default to OFF

Command:

55 5A 0B 01 01 00 0D

Response:

55 5A 0B 01 01 00 0D

Set Channel 2 Power Default to ON

Command:

55 5A 0B 02 01 01 0F

Response:

55 5A 0B 02 01 01 0F

Set Channel 2 Power Default to OFF

Command:

55 5A 0B 02 01 00 0E

Response:

55 5A 0B 02 01 00 0E

Set Channel 3 Power Default to ON

Command:

55 5A 0B 04 01 01 11

Response:

55 5A 0B 04 01 01 11

Set Channel 3 Power Default to OFF

Command:

55 5A 0B 04 00 00 0F

Response:

55 5A 0B 04 00 00 0F

Set Channel 4 Power Default to ON

Command:

55 5A 0B 08 01 01 15

Response:

55 5A 0B 08 01 01 15

Set Channel 4 Power Default to OFF

Command:

55 5A 0B 08 01 00 14

Response:

55 5A 0B 08 01 00 14

Set All Channels Power Default to ON

Command:

55 5A 0B 0F 01 01 1C

Response:

55 5A 0B 0F 01 01 1C

Set All Channels Power Default to OFF

Command:

55 5A 0B 0F 01 00 1B

Response:

55 5A 0B 0F 01 00 1B

Disable Default Power State for Channel 1

Command:

55 5A 0B 01 00 00 0C

Response:

55 5A 0B 01 00 00 0C

Disable Default Power State for Channel 2

Command:

55 5A 0B 02 00 00 0D

Response:

55 5A 0B 02 00 00 0D

Disable Default Power State for Channel 3

Command:

55 5A 0B 04 00 00 0F

Response:

55 5A 0B 04 00 00 0F

Disable Default Power State for Channel 4

Command:

55 5A 0B 08 00 00 13

Response:

55 5A 0B 08 00 00 13

Disable Default Power State for All Channels

Command:

55 5A 0B 0F 00 00 1A

Response:

55 5A 0B 0F 00 00 1A

Query Channel Power Default State (CMD: 0x0C)

Data Field Description:

data[0]

data[1]

data[2]

Channel ID

Enable Default Power State

Default Power Value

Channel_e

0 (false), 1 (true)

0 (OFF), 1 (ON)

Query Channel 1 Power Default State

Command:

55 5A 0C 01 00 00 0D

Response:

Default state disabled:

55 5A 0C 01 00 00 0D

Default OFF:

55 5A 0C 01 00 00 0D

Default ON:

55 5A 0C 01 01 01 0F

Query Channel 2 Power Default State

Command:

55 5A 0C 02 00 00 0E

Response:

Default state disabled:

55 5A 0C 02 00 00 0E

Default OFF:

55 5A 0C 02 00 00 0E

Default ON:

55 5A 0C 02 01 01 10

Query Channel 3 Power Default State

Command:

55 5A 0C 04 00 00 10

Response:

Default state disabled:

55 5A 0C 04 00 00 10

Default OFF:

55 5A 0C 04 00 00 10

Default ON:

55 5A 0C 04 01 01 12

Query Channel 4 Power Default State

Command:

55 5A 0C 08 00 00 14

Response:

Default state disabled:

55 5A 0C 08 00 00 14

Default OFF:

55 5A 0C 08 00 00 14

Default ON:

55 5A 0C 08 01 01 16

Query All Channels Power Default State

Command:

55 5A 0C 0F 00 00 1B

Response:

55 5A 0C 01 01 01 0F
55 5A 0C 02 01 01 10
55 5A 0C 04 01 01 12
55 5A 0C 08 01 01 16

  • Channel 1 Power: Default ON

  • Channel 2 Power: Default ON

  • Channel 3 Power: Default ON

  • Channel 4 Power: Default ON

Set Default Data Connectivity State (CMD: 0x0D)

[!NOTE]

  • When determining channel states after power-up, the default state has higher priority than the power-loss Persistence feature. If the default state feature is enabled, even if the power-loss Persistence feature is also enabled, the system on power-up will still use the default state to decide each channel’s power or data on/off status.

  • When the default state feature is disabled, the channels’ power-on state will be decided by the power-loss Persistence setting. If power-loss Persistence is also disabled (default configuration), then upon power-up all channels will default to OFF.

  • Factory default configuration: all channels’ data lines are connected by default.

Data Field Description:

data[0]

data[1]

data[2]

Channel ID

Enable Default Data Line State

Default Data Line Value

Channel_e

0 (false), 1 (true)

0 (disconnect), 1 (connect)

Set Channel 1 Data Default to Connected

Command:

55 5A 0D 01 01 01 10

Response:

55 5A 0D 01 01 01 10

Set Channel 1 Data Default to Disconnected

Command:

55 5A 0D 01 01 00 0F

Response:

55 5A 0D 01 01 00 0F

Set Channel 2 Data Default to Connected

Command:

55 5A 0D 02 01 01 11

Response:

55 5A 0D 02 01 01 11

Set Channel 2 Data Default to Disconnected

Command:

55 5A 0D 02 01 00 10

Response:

55 5A 0D 02 01 00 10

Set Channel 3 Data Default to Connected

Command:

55 5A 0D 04 01 01 13

Response:

55 5A 0D 04 01 01 13

Set Channel 3 Data Default to Disconnected

Command:

55 5A 0D 04 01 00 12

Response:

55 5A 0D 04 01 00 12

Set Channel 4 Data Default to Connected

Command:

55 5A 0D 08 01 01 17

Response:

55 5A 0D 08 01 01 17

Set Channel 4 Data Default to Disconnected

Command:

55 5A 0D 08 01 00 16

Response:

55 5A 0D 08 01 00 16

Set All Channels Data Default to Connected

Command:

55 5A 0D 0F 01 01 1E

Response:

55 5A 0D 0F 01 01 1E

Set All Channels Data Default to Disconnected

Command:

55 5A 0D 0F 01 00 1D

Response:

55 5A 0D 0F 01 00 1D

Disable Default Data State for Channel 1

Command:

55 5A 0D 01 00 00 0E

Response:

55 5A 0D 01 00 00 0E

Disable Default Data State for Channel 2

Command:

55 5A 0D 02 00 00 0F

Response:

55 5A 0D 02 00 00 0F

Disable Default Data State for Channel 3

Command:

55 5A 0D 04 00 00 11

Response:

55 5A 0D 04 00 00 11

Disable Default Data State for Channel 4

Command:

55 5A 0D 08 00 00 15

Response:

55 5A 0D 08 00 00 15

Disable Default Data State for All Channels

Command:

55 5A 0D 0F 00 01 1D

Response:

55 5A 0D 0F 00 01 1D

Query Default Data Connectivity State (CMD: 0x0E)

Data Field Description:

data[0]

data[1]

data[2]

Channel ID

Enable Default Data Connection State

Default Connection Value

Channel_e

0 (false), 1 (true)

0 (disconnect), 1 (connect)

Query Channel 1 Data Default State

Command:

55 5A 0E 01 00 00 0F

Response:

Default disabled, data line default is connected:

55 5A 0E 01 00 01 10

Default disabled, data line default is connected:

55 5A 0E 01 01 00 10

Default enabled, data line default is connected:

55 5A 0E 01 01 01 11

Query Channel 2 Data Default State

Command:

55 5A 0E 02 00 00 10

Response:

Default disabled, data line default is connected:

55 5A 0E 02 00 01 11

Default disabled, data line default is connected:

55 5A 0E 02 01 00 11

Default enabled, data line default is connected:

55 5A 0E 02 01 01 12

Query Channel 3 Data Default State

Command:

55 5A 0E 04 00 00 12

Response:

Default disabled, data line default is connected:

55 5A 0E 04 00 01 13

Default disabled, data line default is connected:

55 5A 0E 04 01 00 13

Default enabled, data line default is connected:

55 5A 0E 04 01 01 14

Query Channel 4 Data Default State

Command:

55 5A 0E 08 00 00 16

Response:

Default disabled, data line default is connected。

55 5A 0E 08 00 01 17

Default disabled, data line default is connected:

55 5A 0E 08 01 00 17

Default enabled, data line default is connected:

55 5A 0E 08 01 01 18

Query All Channels data line Default State

Command:

55 5A 0E 0F 00 00 1D

Response (scenario 1):

55 5A 0E 01 00 01 10 
55 5A 0E 02 00 01 11 
55 5A 0E 04 00 01 13 
55 5A 0E 08 00 01 17

  • Channel 1 data line: Default disabled, data connected

  • Channel 2 data line: Default disabled, data connected

  • Channel 3 data line: Default disabled, data connected

  • Channel 4 data line: Default disabled, data connected

Response (scenario 2):

55 5A 0E 01 01 00 10 
55 5A 0E 02 01 00 11 
55 5A 0E 04 01 00 13 
55 5A 0E 08 01 00 17

  • Channel 1 data line: Default enabled, data line disconnected

  • Channel 2 data line: Default enabled, data line disconnected

  • Channel 3 data line: Default enabled, data line disconnected

  • Channel 4 data line: Default enabled, data line disconnected

Set Power-Loss State Persistence (CMD: 0x0F)

[!NOTE]

This feature can be toggled by long-pressing Button [2]. When enabled, the current channel states will be saved, and upon re-powering, all channels will restore to their state before power loss.

Data Field Description:

data[0]

data[1]

Fixed

Enable Power-Off Persistence

0x00

0 (false), 1 (true)

Enable Power-Loss State Persistence

Command:

55 5A 0F 00 01 10

Response:

55 5A 0F 00 01 10

Disable Power-Loss State Persistence

Command:

55 5A 0F 00 00 0F

Response:

55 5A 0F 00 00 0F

Query Power-Loss State Persistence (CMD: 0x10)

Data Field Description:

data[0]

data[1]

Fixed

Enable Power-Off Persistence

0x00

0 (false), 1 (true)

Command:

55 5A 10 00 00 10

Response:

  • Power-loss Persistence enabled:

55 5A 10 00 01 11

  • Power-loss Persistence disabled:

55 5A 10 00 00 10

Set Device Address (CMD: 0x11)

[!NOTE]

  • The device address is used to identify and distinguish each hub when multiple hubs are connected.

  • The address is user-defined and must be in the range: 0x0000 - 0xFFFF.

  • The default address is 0x0000.

  • Supported Products: All products (including SmartUSBHub Pro and FlexConnect) support the device address feature.

Usage:

  1. Assign a unique device address to each hub (this only needs to be done once).

  2. In your program, sequentially read the device addresses of all connected hubs and bind them to their respective serial ports or instances.

  3. After completing the above steps, each hub will have a clear and consistent index and mapping.

Connection Topology

Topology Structure 1

  • The upstream data ports of multiple hubs are connected to a higher-level hub.

  • The command ports of multiple hubs are connected to a higher-level hub.

  • Two top-level hubs are connected to the host.

The number of available downstream ports in this topology is 4n.

Topology.001

Topology Structure 2

  • The upstream data port of the next hub is connected to the downstream data port of the previous hub.

  • The command ports of multiple hubs are connected to a higher-level hub.

  • The upstream data port of the first hub is connected to the host.

  • The top-level hub in the control chain is connected to the host.

The number of available downstream ports in this topology is 3n+1.

Topology.002

Data Field Description:

data[0]

data[1]

Address [15–8]

Address [7–0]

Example:

Set the hubs device address to 0x0001

Command:

55 5A 11 00 01 12

Response:

55 5A 11 00 01 12

Get Device Address (CMD: 0x12)

Data Field Description:

data[0]

data[1]

Address [15–8]

Address [7–0]

-

-

Example:

Get the hub’s device address

Command:

55 5A 12 00 00 12

Response:

55 5A 12 00 01 13

The device address of this hub is: 0x0001

Set Operation Mode (CMD: 0x06)

[!NOTE]

The device has two operation modes:

  1. Normal Mode: Each channel can be controlled independently.

  2. Interlock Mode: Channels are mutually exclusive; only one channel can be on at a time.

    • This setting is retained after power off.

    • It can be toggled by long-pressing Button 1 (>3 s). The LED indicator pattern reflects the current mode.

    LED Indicator patterns:

    Blink Pattern

    Meaning

    0.5 s on, 0.5 s off

    Normal operating mode

    0.25 s on, 0.25 s off

    Channel interlock mode

    Momentary off flash (overlaid)

    Receiving a control command frame

Data Field Description:

data[0]

data[1]

Fixed

Operating Mode

0x00

0 (Normal Mode), 1 (Interlock Mode)

Set to Normal Mode

Command:

55 5A 06 00 00 06

Response:

55 5A 06 00 00 06

Set to Interlock Mode

Command:

55 5A 06 00 01 07

Response:

55 5A 06 00 01 07

Query Operation Mode (CMD: 0x07)

Data Field Description:

data[0]

data[1]

Fixed

Operating Mode

0x00

0 (Normal Mode), 1 (Interlock Mode)

Command:

55 5A 07 00 00 07

Response:

  • Device in Normal Mode:

55 5A 07 00 00 07

  • Device in Interlock Mode:

55 5A 07 00 01 08

Reset Factory Settings (CMD: 0xFC)

Data Field Description:

data[0]

data[1]

Fixed

Fixed

0x00

0x00

Command:

55 5A FC 00 00 FC

Response:

55 5A FC 00 00 FC

Query Firmware Version (CMD: 0xFD)

Data Field Description:

data[0]

data[1]

Version [15–8]

Version [7–0]

-

-

Command:

55 5A FD 00 00 FD

Response:

55 5A FD 00 0F 0C

Firmware Version: 15

Query Hardware Version (CMD: 0xFE)

Data Field Description:

data[0]

data[1]

Version [15–8]

Version [7–0]

-

-

Command:

55 5A FE 00 00 FE

Response:

55 5A FE 00 03 01

Hardware Version: 3 / V1.3

Glossary

Term

Description

USB Differential Signal Pair (D+/D−)

The differential pair used for USB data transmission; the core physical signal lines.

Differential Pair Switch

Controls the connection state of the D+/D− lines.

VBUS Power Control

Controls a channel’s USB power supply state (on/off).

Power Switch State

Indicates whether the VBUS power is currently on.

Channel

A downstream port of the hub.

USB CDC

USB Communications Device Class – a standard protocol that virtualizes a USB device as a serial port.

Channel Voltage

The sampled VBUS voltage value (unit: mV).

Channel Current

The sampled output current value (unit: mA).

USB Signal Control

Controlling D+/D− connectivity while retaining power.

Signal Line Switch State

The current connectivity status of the D+/D− lines.

Channel Interlock Mode

A mutual-exclusion mode allowing only one channel to be on at a time.

Power-On Default State

The initial on/off state of each channel after power-up.

Default Power State

The default on/off state of VBUS power when the system powers on.

Default Signal State

The default on/off state of D+/D− data lines when the system powers on.

Power-Loss State Persistence

Whether the system saves the state before power loss and restores it after power-up.

Button Control Permission

Whether physical button control of channels is allowed.

Upstream Port

The port that connects to the host (e.g., PC).

Downstream Port

The port that connects to a peripheral (USB device).

Software Command Control

Control via software commands sent over the serial interface.

Operation Mode

The device’s mode of operation (Normal Mode or Interlock Mode).

Normal Mode

Each channel can be controlled independently.

Interlock Mode

Channels are mutually exclusive; only one port can be on at a time.

Firmware Version

The version of the currently running firmware.

Hardware Version

The version of the hardware circuitry used.

UART Communication

Using a USB virtual COM port to send control commands.

Command Frame / Protocol Frame

A complete communication packet structure used for control.

Simulated Hot-Plug

Simulating hot-plug scenarios by controlling data connectivity while maintaining power.

FAQ:

Q: A USB storage device (e.g., flash drive) is connected, but the computer does not detect any device.

A: Make sure the [6] USB 2.0 Upstream Port is connected to the computer.

sc1

Q: Unable to find the serial (COM) device.

A: Is your computer running Windows 7 or an earlier version? If so, please install the legacy driver. Also, check that the [5] Device Communication Port is connected to the host.

image-20250614203937364

Q:The hub occasionally disconnects from the computer.

A:Check if the connected device’s power draw is too high. If it exceeds the output capability of the computer’s USB port, connect a 5 V power adapter with sufficient wattage to the [4] Auxiliary Power Port for additional power.

image-20250614202517699

Note:

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