June 09, 2012

First Taste of Pi

Posted at June 9, 2012 04:28 PM in Computers .

So after tracking the online buzz about the Raspberry Pi for a long time, I finally got my hands on one. It was a bit finicky to get set up. To keep costs and power consumption of the device down, a number of trade-offs and sacrifices have been made. Things to keep in mind for anyone starting off with the Pi:

1) It does not come with a power supply. It uses a Micro-USB connector for the power, BUT needs more than the standard 500ma of current that is typically provided via USB. The specs say the minimum current required is 700ma, but based on what I have read and experienced, you need a power adapter that provides at least 850ma (with 1A or greater being ideal) to ensure there's enough power for even simple USB devices connected to the Pi (e.g. keyboard/mouse). I am using a 2A Xentris Micro-USB charger.

2) Even using a charger with plenty of power, the Pi is limited to providing a maximum of 150ma of power to each USB port. Some keyboards, particularly those with USB hubs built in, can reach that limit and cause issues. A cheap and simple keyboard is the best bet. I am successfully using a Logitech keyboard without a USB hub which has current draw listed on the bottom as 100ma.

3) The HDMI out works quite well connected to TVs. I had some difficulties connecting to a monitor using a HDMI->USB adapter -- there was lots of noise and interference on the screen. I tried boosting the HDMI output signal, as per the Raspberry Pi Wiki, but couldn't get it to work until I used an actual HDMI->DVI cable ($7 from AmazonBasics). For some reason the adapter (made by Rocketfish) was causing enough signal loss that the monitor was having problems.

4) Everything is set to UK settings. The Pi foundation is a UK based charity so I suppose that's to be expected, but remember to change your timezone and keyboard layouts, if you are based elsewhere (such as the US).

5) The ARM processor is not very powerful. If you have used embedded boards with more powerful ARM chips (including many modern smartphones), it will seem particularly underwhelming. However, for the cost, it's decent. The GPU, which supports 1080p displays and H.264 decoding in hardware, is what really sets it apart, especially in this price class. I plan to spend a bit of time looking at how I can best leverage the GPU, which supports OpenGL 2.0 ES, OpenVG, and OpenMax software APIs.

More to come...


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