A comment in
http://madmodder.net/index.php/topic,11315.0.html spawned questions regarding "Yuri's DRO" (
http://www.yuriystoys.com/p/android-dro.html ). While most questions are answered there and the man himself answers questions on his blog quickly, usually, maybe we can collect experience of other MadModders in this topic.
My personal experience in bold:
So you built Yuris dro project for an android.....which arduino did you use? I plan on using a nano.....
I used a nano myself, works fine.
What about pcb? Did you make a custom board or use a shiels?
Custom PCB, I'm not into shields. Nothing special, just something to "connect the dots" between the Arduino, the BT module and the cables.
I'd like to make a dedicated board using the nano and bt adapter.....
Yeah, that's what I did and it works fine.
What connectors did you use for the scales?
USB cables of the wrong type, unfortunately. Meaning, I soldered the wrong jacks on the board (surface mounted and thus hard to correct without starting from scratch). I later found out that it is really hard to actually find cables for it. 
But with a bit of foresight, this should be no problem.
The only problem I have is one that is reported frequently with the particular type of scales used with this solution (iGaging, in my case). Meaning, electromagnetical noise, especially when switching on/off motors, sometimes makes the scales lose their position. It's probably something related to ground loops or whatever, and could probably be fixed by using plastic instead of metal to fix them to the mill. But aside from that I am very happy. The whole system is absolutely lag free and "real time" and seems to be 1/100mm resolution "end to end". At least the resolution of the DRO is higher than what I can realistically expect to achieve with the mill itself, considering flex...
