20 port usb hub bitcoin wiki

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A number of low-cost powered USB hubs are known to have 20 port usb hub bitcoin wiki problems. Members of the Raspberry Pi forums have reported low power or no power at all in some cases. Please note that these 20 port usb hub bitcoin wiki not take into account powering the Raspberry Pi from the hub, in addition to its peripherals.

If you use a powered hub and the Raspberry Pi PSU together consider powering them from the same power bar with switch, so you can turn them on simultaneously. Recently, two new hubs have been designed and manufactured specifically for the Raspberry Pi. Guaranteed to provide no back power to the unit. Please check known workarounds here before adding to the list.

In this case it may be desirable to power the Raspberry Pi from the USB hub instead of in the usual manner from a separate power supply. This power hookup requires two USB cables between Hub and Raspberry Pi, which are both shown on the power hookup schematic. The schematic also shows two important features of the USB hub internal power wiring that are required to 20 port usb hub bitcoin wiki power the Raspberry Pi.

First, the hub coaxial power input directly connects to the USB A output ports. Second, the hub diode prevents back-powering, that is, current cannot flow in the reverse direction from the hub coaxial power connector back out to the micro B input port 20 port usb hub bitcoin wiki into the Raspberry Pi.

This section describes two tests that will verify that a USB hub has the correct power circuitry. In addition to the USB hub, Raspberry Pi, and high and low power load resistors, these tests require a digital voltmeter and 3 patch cords, one of each which terminates on one end with a coaxial power plug, a USB A plug, and a mini B plug.

It's possible to power all tests from a coaxial jack connected to the hub power adaptor coaxial plug, but it will be more convenient to use a standard bench power supply with voltage readout and adjustable current limit. The output power test has two parts, which are both shown on the output power test schematic. The first and simpler setup powers the hub directly from the hub power adaptor and 20 port usb hub bitcoin wiki that in its normal operating configuration the hub will provide sufficient power.

As shown on the schematic there must be at least 4. This is most easily accomplished with a bench power supply and coaxial power plug patch cord. Patch cord the test circuit as shown on the input diode test schematic.

This test simulates the hub in bus-powered mode. The specification also requires that such low-power devices have a minimum operating voltage of 4. The diode voltage drop can be measured between the pin 1 patch cord wire of the mini B input plug and the pin 1 wire of the type A output plug or calculated as the difference between voltages measured across pin 1 and 5 wires of the input plug and pin 1 and 4 wires of the output plug.

The presence of the 0. A setup very similar to the output power test can check for reverse leakage current and further strengthen the evidence that the hub internal circuitry includes a diode at the position indicated in the test schematic. As shown on the output power test schematic power the hub through its coaxial power input and optionally put the 1 unit power load resistor on an output port. This is consistent with a high voltmeter impedance limiting both the reverse leakage current and reverse bias voltage to a very small values.

Here are the measurements:. Seems very good, tested with: The PSU for the hub is a 2. Comes with a 2. This is the same chip used as in the Pimoroni PiHub. Contra the report under "Problem Hubs" below, I do not have any trouble with wired ethernet on a Model B pi, 3.

This is the only powered hub on shelves at Radioshack as of early It is also powering a 1 TB disk. All 7 ports are working. Powers the Rapsberry Pi and an 2. I already tried to connect another HDD without problems even if is not yet been mounted on linux. Failed diode backpower test. There is a video showing this hub powering both the Raspberry Pi several peripherals at once [14].

No back-voltage on upstream connection. Widely used with success on the Pi. Plugable 4 Port Hub with Battery Charging 1. US plugs version only.

USB Audio 20 port usb hub bitcoin wiki tested and working. Plugable 10 Port USB 2. Get their USB 2. Since Pi can't benefit from USB 3. Plugable 7 Port USB 3. Small solid aluminium enclosure. Trust Plata 4 port USB 2. Screens - Cases - Other Peripherals 20 port usb hub bitcoin wiki, mouse, hub, wifi Retrieved from " https: Navigation menu Personal tools Log in Request account.

Views Read View source View history. This page was last modified on 18 Decemberat This page has been accessedtimes. Privacy policy About eLinux. Powers the pi quite well, 4. Does backfeed the mini USB port. No backfeed, can power the RPi.

No problems powering the pi itself. Cascaded hub, only 3 ports work [2] [3]. Works with Raspbian for powering webcams. Tested only backpower - works well. Very small USB Hub. Has separate USB In port, in theory should prevent backfeeding but that is not verified. The high-power 4 A power adapter makes this a tempting purchase, but some users report problems 20 port usb hub bitcoin wiki devices with a USB 3.

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A USB hub is a device that expands a single Universal Serial Bus USB port into several so that there are more ports available to connect devices to a host system, similar to a power strip. USB hubs are often built into equipment such as computers , keyboards , monitors , or printers.

Physically separate USB hubs come in a wide variety of form factors: In the middle case, there are "short cable" hubs which typically use an integral 6-inch cable to slightly distance a small hub away from physical port congestion and of course increase the number of available ports. Laptop computers may be equipped with many USB ports, but an external USB hub can consolidate several everyday devices like a mouse and a printer into a single hub to enable one-step attachment and removal of all the devices.

USB ports are often closely spaced. Consequently, plugging a device into one port may physically block an adjacent port, particularly when the plug is not part of a cable but is integral to a device such as a USB flash drive.

A horizontal array of horizontal sockets may be easy to fabricate, but may cause only two out of four ports to be usable depending on plug width. Port arrays in which the port orientation is perpendicular to the array orientation generally have fewer blockage problems. External "Octopus" or "Squid" hubs with each socket at the end of a very short cable maybe 2 inches long , or "star" hubs with each port facing in a different direction, as pictured avoid this problem completely.

A hub can be used as an active USB repeater to extend cable length for up to 5 metre 16 feet lengths at a time.

Active cables specialized connector-embedded one-port hubs perform the same function, but since they are strictly bus-powered, externally powered non-bus-powered USB hubs would likely be required for some of the segments. A bus-powered hub passive hub is a hub that draws all its power from the host computer's USB interface. It does not need a separate power connection.

However, many devices require more power than this method can provide and will not work in this type of hub. It may be desirable to use a bus-powered hub with self-powered external hard-disk units, as they may not go into sleep mode immediately upon computer shut-down or sleep mode when using a self-powered hub since they will continue to see a power source on the USB ports when using a self-powered hub. If a device requires more units of current than the port it is plugged into can supply, the operating system usually reports this to the user.

In contrast, a self-powered hub is one that takes its power from an external power supply unit and can therefore provide full power up to mA to every port. Many hubs can operate as either bus powered or self powered hubs. However, there are many non-compliant hubs on the market which announce themselves to the host as self-powered despite really being bus-powered.

Some self-powered hubs do not supply enough power to drive a mA load on every port. For example, many seven port hubs have a 1A power supply, when in fact seven ports could draw a maximum of 7 x 0.

Designers assume the user will most likely connect many low power devices and only one or two requiring a full mA. On the other hand, the packaging for some self-powered hubs states explicitly how many of the ports can drive a mA full load at once. For example, the packaging on a seven-port hub might claim to support a maximum of four full-load devices.

Dynamic-powered hubs are hubs which can work as bus-powered as well as self-powered hubs. They can automatically switch between modes depending on whether a separate power supply is available or not. While switching from bus-powered to self-powered operation does not necessarily require immediate renegotiations with the host, switching from self-powered to bus-powered operation may cause USB connections to be reset if connected devices previously requested more power than still available in bus-powered mode.

To allow high-speed USB 2. High-speed devices should fall back to full-speed USB 1. While high-speed hubs can communicate at all device speeds, low and full-speed traffic is combined and segregated from high-speed traffic through a transaction translator. Each transaction translator segregates lower speed traffic into its own pool, essentially creating a virtual full-speed bus. Having multiple translators is a significant benefit when one connects multiple high-bandwidth full-speed devices.

It is an important consideration that in common language and often product marketing USB 2. However, because the USB 2. Thus, not all USB 2. Each hub has exactly one upstream port and a number of downstream ports. The upstream port connects the hub directly or through other hubs to the host.

Other hubs or devices can be attached to the downstream ports. During normal transmission, hubs are essentially transparent: This way, what is sent by the host is received by all hubs and devices, and what is sent by a device is received by the host but not by the other devices an exception is resume signalling.

Downstream routing has been changed in USB 3. A route string sent in the packet header allows a USB 3. Hubs are not transparent when dealing with changes in the status of downstream ports, such as insertion or removal of devices. In particular, if a downstream port of a hub changes status, this change is dealt with in an interaction between the host and this hub; the hubs between them act as transparent in this case.

To this aim, each hub has a single interrupt endpoint "1 IN" endpoint address 1, hub-to-host direction used to signal changes in the status of the downstream ports. When the host polls this interrupt endpoint, it learns that the new device is present. It then instructs the hub via the default control pipe to reset the port where the new device was plugged in.

This reset makes the new device assume address 0, and the host can then interact with it directly; this interaction will result in the host assigning a new non-zero address to the device. For example, if a USB 1. However, the default design is that all lower-standard devices share the same transaction translator and thus create a bottleneck, a configuration known as the single transaction translator. Consequently, multi transaction translators Multi-TT were created, which provide more transaction translators such that bottlenecks are avoided.

Most USB hubs use one or more integrated controllers ICs , of which several designs are available from various manufacturers. Most support a four-port hub system, but hubs using port hub controllers are also available in the industry. The root hub is the first tier, and the last devices are on the seventh tier, which allows 5 tiers worth of hubs between them. The maximum number of user devices is reduced by the number of hubs. Also available are so-called "sharing hubs", which effectively are the reverse of a USB hub, allowing several PCs to access usually a single peripheral.

They can either be manual, effectively a simple switch-box, or automatic, incorporating a mechanism that recognises which PC wishes to use the peripheral and switches accordingly. They cannot grant both PCs access at once. Some models, however, have the ability to control multiple peripherals separately e. Only the simpler switches tend to be automatic, and this feature generally places them at a higher price point too.

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