Why do I buy on Ebay from Chinese sellers?

Ebay is an interesting place when it comes to shopping for electronic parts. You can find dirt cheap components from sellers on the far East, but you can also buy a reel of metal slugs instead of real ICs. Having had some bad experiences with shady sellers and long shipping times, I generally try to buy from US sources. The prices are not that great, but at least I don't have to wait 4-6 weeks for delivery, I tend to trust US sellers more (even if they sell the same Chinese crap), and I prefer to shop locally instead of pumping extra dollars into the Yellow Dragon's economy. However, there are days that I just want to say "fuck the political correctness" and go ahead and stuff the shopping cart with parts sold by all the Liang Mings of Ebay. Just like today.


Using VirtualBox to install OS for an embedded system

Embedded systems are fun to play with, but installation of the OS can be a real pain. In my case the OS was not a big problem (I'm using a plain, old, boring PC hardware, after all), but as usual, the devil lurks in the details. In my case none of the monitors I have at home was able to display the video signal from the board (23" Dell LCD went just blank, while 17" LCD at least showed a message about unsupported video mode.) The only device that worked properly was a projector. Being a lazy brat as I am, I decided to not to stand at the projector holding the keyboard in one hand and the board in the other, and hack the entire process without touching the target board at all. Enter VirtualBox, a full PC system in a small window on the monitor.


Keep your Red Pitaya cool

Red Pitaya is small measurement instrument built around Xilinx' Zynq SoC integrating a dual-core Cortex-A9 CPU, peripheral devices and FPGA fabric. The chip drives two 14-bit DA converters and two 14-bit AD converters at 125MSps. Switching transistors in CMOS circuits at such speed requires quite a lot of power, which is dissipated in a form of heat. The board gets hot. Even though the SoC and the converters are cooled by a heat spreader, after several minutes the input connectors and the heat sink become too hot to touch.