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I2C VGA Adapter

tags: debian, i2c, vga, hdmi, dvi, hardware, electronics, logic level converter, linux 2012-07-07 08:41 by sre

For one of my projects I’m making heavy use of I²C devices. For development it would be nice to connect them to my notebook and develop and debug the sourcecode natively.

Luckily I remembered that all common display connection standards (VGA, HDMI, DVI) have an I²C control channel. In the linux kernel these pins are exported as I²C device by the graphic card driver. For example my intel driver exports 8 I²C devices.

So the only hardware needed to use an I²C device on my notebook is a cheap VGA cable. After cutting it in half we have two I²C adapters. I decided to create one cable for 5V I²C devices. This one is already done after cutting the cable in half. I soldered a jumper wire connector on the four needed wires and removed the others.

the fatal ways of the sheevaplug

tags: hardware 2010-07-17 19:56 by lhw

It’s been about 10 month now since I ordered 7 SheevaPlugs, a plug sized computer, from GlobalScale. Everything ran smoothly for the next months till about 2 weeks ago when it suddenly became unresponsive and spammed the network with packages slowing down my other clients. A few more days later and it broke down completly with a blinking green LED. As it turned out this was already the second dead SheevaPlug after the one sre got back then.

After just about 1 minute search you will find the following thread on plugcomputer.org, the official forums: Is my sheevaplug dead ???. After reading the thread for a while it was obviously the power supply units fault. Seeing some of the pictures its a miracle that thing worked in the first place. The average lifetime of the PSU is about 9 month according to the thread. NewIt.co.uk the british GlobalScale reseller even offers the PSU as single product nowadays.

I first thought about buying on of those but then I probably would have gotten the same faulty PSU again. So I tried locating the defect parts on my one. I replaced an electrolytic capacitor and checked the output under stress with a 12cm fan, which seemed to work. But not when connected to the SheevaPlug which seems to suck that PSU to its uppermost limit. So there were more faulty parts which I couldn’t locate beneath all that brownish/blackish glue.

In the end I removed the internal openframe PSU and connected it to an cheap external power supply. As board connector the plug from an old PC case speaker fits perfectly.

And here some pictures of the now again working SheevaPlug: