Thank you for lots of comment at hackaday.com for improve SDuino function.

I have some plan, for example implementation of direct binary writing through SD card interface via iSDio or adding new function like putting some kind of sensor on it.

During making prototype, I made two variant. (at this moment, the function is same as previous original one.)

First one is, 16MHz clock version using seramic resonator, but the thickness of ceramic resonator is too thick to put into SDcard case, and I have to abandon it. (Substrate is already too thin, 0.4 mm thick is grinded down to around 0.2 mm)

Next one is, almost the repetition of the first prototype but I may add I2C device for it. (not implemented yet) This case, I pursue ultimate thin-ness of substrate and finally corner is getting folded as you see.. ;-)

And, now I would move on the latest topic.

As introduced before, The writing to SD card was via general USB-TTL converter, but as you see, it is not small yet.

This time, I made

Smart SDuino writer!

It looks like just a SD card reader but inside it I put FTDI chip and simple put SDuino and connecting to computer, we can upload sketch.

Final shape (covered by heat-shrink tube) I believe it is enough smart!

The actual operation can be seen in the following move, have fun!

Have fun!