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Review Raspberry Pi accessory specialist Pimoroni reckons it has the answer to one of the tiny ARM-based computer’s signal limitations: too few USB ports for all the add-ons you might want to hook up to it.

Pi users have dealt with only having a pair of USB 2.0 ports - there's only one on the cheapest, the Model A Pi - by connecting a low-cost USB hub. Pimoroni reckons most of the hubs users attach are not up to snuff: they’re not sufficiently powerful, being driven by a transformer pumping out no more than 1 or 2A, or deviate from the USB spec in ways that hinder compatibility.

Pimoroni’s Pi Hub ... get a load of that logo type

Not so its own hub, launched on Monday, the company claims. According to Pimoroni, its hub has been designed to be as compatible with the Pi and the USB standard as possible. Oh, and it also looks exactly like the Raspberry Pi logo - which just so happens to have been designed by Pimoroni co-founder Paul Beech.

The PiHub sports four full-size USB 2.0 ports, and it connects to the Pi using a narrow USB ‘B’ jack - the kind usually found on printers. Four ports on the hub and, with the right Pi, a fifth on the computer itself provides plenty of scope for input devices, wireless adaptors, printers and extra storage.

Two USB 2.0 ports on this side, two more on t’other

The hub is able to operate directly off the power flowing through the Pi’s USB port, which I found fine for connecting low-power kit such as a keyboard and a mouse, or with a bundled full-blooded 3A AC adaptor.

The adaptor is actually larger than the hub itself, but its bulk means there’s plenty of juice for whatever power-hungry thing you may hook up to the hub, such as USB-powered external hard drives - and, indeed, up to four Raspberry Pis themselves, says Pimoroni.

The bundled AC adaptor is large, but Amp-tastic

I tried the PiHub in bus-powered mode first. While it kept my mouse and keyboard working, it didn’t provide enough power for a small USB stick I wanted to use too. No matter: with the hub allowing the main peripherals to be shared by a just one of the Pi’s USB ports, I had the second port on my Model B Pi free for the stick. Normally I have to unhook the keyboard to make room for the USB storage.

Of course, with the AC adaptor hooked up to the hub too - it connects to a jack in one of the Pi logo’s green leaves, as does the input USB connection - there’s no trouble getting sufficient power to all the hub-connected devices.

More ports for your Pi - and power too

So I soon had not only my mouse and keyboard connected and powered, but also my recharging phone, a bus-powered external USB hard drive and - get this - the Pi itself, the micro USB input cable being fed by Pimoroni’s 3A adaptor via the hub. Smart: that’s one less power supply unit I need.

Inside, the PiHub has a multi TT (Transaction Translator) chip for lifting slow USB 1.1 traffic up onto the high-speed USB 2.0 bus. Many hubs share a single TT among all their ports, forcing them all to share a single 12Mb/s data pipe. Having multiple TTs means that each USB 1.1 device connected gets its own, full 12Mb/s link.

Multi TT inside

In the world of USB 2.0 hub design, this is considered A Very Good Thing. Apart from giving USB 1.1 kit sufficient bandwidth, a multi TT also ensures that the many protocols running over USB get the bandwidth they expect. The upshot: you’ll get better performance out of hub with a multi TT than one with a single TT, which is what most cheap hubs contain.

Not that Pimoroni’s PiHub is pricey. It’ll set you back a mere 20 quid - or £13.95 if you don’t need the 3A AC adaptor and the USB A-B adaptor cable. You can get the AC adaptor with either UK or European power pins. The hub itself is made in the UK by component company Cyntech, and ten per cent of the proceeds are passed on to the Raspberry Pi’s educational endeavours. ®

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