In search of the perfect hub

    Having analyzed the publication “ Briefly on the ORICO Ideal 7-Port USB 3.0 Hub ” and its comments , we can say that the concept of the ideal USB 3.0 hub (shorter and better - the hub) is reduced to two postulates:
    • any USB device requiring charging can be powered by connecting to an arbitrary port on the USB hub;
    • all ports of the USB hub can exchange at any speed, regardless of the status of other ports of this hub.

    Let's figure out how the model of the ideal hub correlates with reality?

    Specifications and circuitry


    The requirement to charge peripherals connected to a USB hub is categorically related to the presence of external power. Today, host controllers in most cases are located on compact devices that can work independently. In this regard, the ideal situation would be when low-power tablets, laptops, and smartphones shared their intellect with a gluttonous USB peripheral, and an intermediate and by no means weak link in the form of a USB 3.0 hub powered from a network would meet the satisfaction of appetites.

    Battery Charging Specification

    To solve this problem, the IT community has proposed two specifications that, with a number of reservations, are gradually being implemented. This issue is well covered in online publications, in particular, an applied research on the implementation of Battery Charging is described in the article “ Charging a tablet from USB: the question remains open ”. The power model described in the Universal Serial Bus Power Delivery Specification is designed to provide up to 100 watts over USB. With its implementation, the situation is even worse. In fact, it is not yet necessary to rely on a current of 5 amperes and a supply voltage of 20 volts from USB.

    imageWhen purchasing a USB 3.0 hub, you should take care that the purchase not only pleases the eye, but also charges everything that can be powered from the USB bus. Unfortunately, in the store it is not always possible to find out on which chipset the device is assembled. But even in cases where the manufacturer of the controller and its model are known, often there is not enough information about the support of the Battery Charging specification. As for USB controllers from VIA Labs, this gap is partly covered in the article “ Hub USB 3.0: the difficulties of choice ”. In a detailed analysis of the VIA controller descriptions, one detail is alarming: the documentation uses the phrase Vendor Specific Charging Modes , which refers to Apple products and RIM (read - BlackBerry). There is a suspicion that not all USB hubs have this functionality - inherent quality.

    Power Circuit Design

    Not the least importance when choosing the perfect USB hub are circuit solutions. The article about ORICO mentioned above already focused on the fact that power switching should eliminate a short circuit between the + 5V lines of the computer’s USB port and the hub power supply. Equally important is the competent implementation of power circuits to ensure the required load capacity. We have already encountered this problem, getting acquainted with the features of the tablet ASUS Vivo Tab TF600T. It seems that the Vendor Specific USB charging models set strict requirements for the load capacity of the USB port.

    As a consequence of all of the above, one of the requirements for an ideal USB hub should be effective current protection. Obviously, the use of self-healing fuses is preferable to fuses requiring replacement after a power failure.

    Risk factor

    When choosing a USB 3.0 hub, the potential owner should be warned against a blunder - rely on the possibility of charging USB devices solely on the basis of the stated support for the Battery Charging specification by the hub controller. It also depends on factors not related to the functionality of the chipset: from the power supply circuits, from the contents of the EPROM, the quality of the connecting conductors and connectors, the suppression of power interference during abrupt current changes, fuse ratings. But the main thing is from the implementation of a signaling protocol that uses the Data + line and the USB 2.0 Data- interface to organize the intelligent interaction of charging and rechargeable devices. And only the last factor is determined by the functionality of the hub controller chip.

    USB 2.0 and SuperSpeed ​​simultaneously


    In the comments to the article about ORICO, the most important issue of the functionality of the USB3 hub is raised: its ports cannot exchange data at any speed. Connecting a USB2 device reduces the exchange rate on other ports from SuperSpeed ​​to HighSpeed.

    But the requirements for independent operation of the ports of an ideal USB hub do not contradict the specification for a universal serial bus! According to this document, the USB3 hub consists of two relatively interdependent hubs providing USB2 and USB3 connections. The USB 3.0 specification, making an exception for the USB3 hub, unlike a regular USB device, allows it to use USB2 and USB3 lines simultaneously. This is a prerequisite for ensuring the simultaneous operation of HighSpeed ​​and SuperSpeed ​​modes.

    In connection with this quote fromsuperuser.com , which talks about the non-trivial task of developing an independent model of a USB3 hub, is countered by a quote from the original source: “ Note that a USB 3.0 hub is the only that is allowed to operate at both USB 2.0 and SuperSpeed ​​simultaneously ”:

    USB 3.0 Specification for Independent Operation of USB Ports (Speed ​​Dependent Descriptions)

    USB3 Hub Software Model

    The USB 3.0 hub should be built on the basis of a unified software model defined within the Hub Class Specification. Its basic functionality should be provided before the OS starts under the control of firmware and other procedures that work before loading device-specific drivers.

    The criterion in this case should be the provision of hub support by firmware within the Legacy BIOS and UEFI, the ability to boot the OS from devices connected through the ports of this hub, as well as the use of a keyboard or mouse in CMOS Setup procedures.

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