Gottfried writes in about the DS brut -

Hi there, at the beginning of this year, Gordan Savicic (who did the infamous “contraint city” wifi-nds-corset project, featured on MAKE blog, WMMNA and others) and myself desperately needed an I/O card for the Nintendo DS for a project of ours. So we set out to build one, reverse engineered all missing bits of documentation, build prototypes, wrote software for it and finally had a small batch of our printed circuit board designs made in China, we now want to share with our fellow makers. The device allows for easy, Arduino-style access to all kind of hardware interfaces, like an UART, GPIO pins, PWM output, analog/digital converters, I²C bus – which allow you too get readings from all kinds of sensors and control devices, all directly from within Nintendo DS code. Best of it: it’s all open, and the code running on the embedded Atmega168 chip can be very easily updated/tinkered around with, using available and free tools.