Raspberry Pi Official Case

Re:Raspberry Pi Official Case by Animats on Wednesday June 17, 2015 @03:08AM (#9730400)

The Raspberry Pi is really a tablet system on a chip mounted on a breakout board. You can get $50 tablets easily. Some are even cheaper.[1] There are various USB to GPIO devices.[2] If you need a display and user input, it may be easier to start with a low-end tablet than with a Raspberry Pi. The main problem is 1) getting Android out and a more developer friendly OS such as Ubuntu Touch in, and 2) finding a tablet which is a USB master. (Phones are usually USB slaves. Laptops are usually USB masters. Tablets come in both flavors, plus the new "USB on the Go", which allows the master and slave to switch.)

A nice product package would be a low-end tablet with some general Linux distro pre-installed and a USB to GPIO device, priced around $75. That would be useful for when you want a little machine with a UI to control something. Anything like that on the market?

[1] http://www.amazon.com/dp/B00GART8LE/?tag=twup-20 [2] http://numato.com/8-channel-usb-gpio-module.html

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Re:Raspberry Pi Official Case by friendzis on Wednesday June 17, 2015 @06:42AM (#9730945)

Most, if not all, embedded SoCs I have laid my hands on as an EE were either OTG or slave

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Re:Raspberry Pi Official Case by Animats on Wednesday June 17, 2015 @02:26PM (#9734178)

A reasonable number of USB master tablets exist. There's a web site for tablets with USB-A (master) sockets.[1]

[1] http://www.tabletswithusbports.net/

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Re:Raspberry Pi Official Case by friendzis on Thursday June 18, 2015 @10:34PM (#9742733)

Not to appear picky but I think this needs to be clarified a bit. USB uses synchronous (request-response) wire protocol and one side is always requesting, another responding - hence master and slave. This is not runtime configurable/negotiatable.

Traditionally USB transceivers were designed as either master or slave (host/peripheral), though with the rise of smart peripherals (embedded/mobile devices) came need for both in one device. Manufacturers could design product with 2 different USB transceivers or use one that is configurable to either master or slave.

If you examine any mini/micro USB port/plug you will find 5 pins, and 4 pins on a large (both A and B). That extra pin is actually a toggle for OTG transceiver mode. Of course manufacturers can decide to internally wire transceiver to any mode and expose only data/power pins, but that does not stop transceiver from being OTG. Exactly this is done in top Android tables from mentioned site - they have nVidia Tegra SoC which actually uses OTG transceivers.

I am not intimate with PC hardware (would expect master-only transceivers), but, as I have said before, all embedded SoCs I have laid my hands on (not too many) used either slave-only or OTG transceivers.

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Re:Raspberry Pi Official Case by fragmede on Wednesday June 17, 2015 @05:13PM (#9735360)

USB 'on the go' was first standardized in 2001. It's not exactly new. Given commonalities between phones and tablets, many phones can do USB OTG, though they sometimes need root to be properly useful.

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