Good observations! The latency is due to a number of factors, not least of which is my really inefficient code. I made it overly simple to understand and, in doing so, left it a little bloated. There’s also a delay of 50 milliseconds in the main loop and another small delay on either side of the shift register ShiftOuts. These delays aren’t necessary, I had them in there when I was debugging and just left them in. Remove those delays and you should already notice a huge difference in lag.
Changing the baud rate helps as well, I’ve run it on a 16MHz Arduino to 115200 with no problems. And yes, These would work great with XBee (good idea…)
Oh, as for the touch screen: yes, it took me back to my Handspring Visor days. Resistive touch doesn’t seem nearly as miraculous now as it did then. It work quite well, though. The cuts were really just an impatient videographer trying to whittle down the time on an already lengthy video. I also had some trouble because I was using it at an unnatural angle for the benefit of the camera. I would suggest making screen-widgets larger, though, for Ease-of-use. I was probably on the edge of “too small” for finger touch (although a stylus would work)
The other thing to keep in mind is that there’s not much need to cram everything onto the screen since you can have multiple forms and flip between them.
I should also mention that the way I handled the communication with Arduino is the way that’s easier for most beginners to “get” but when you’re building your project, you can select under the object properties whether or not a control will “send a report” when it’s changed. So the screen can actually initiate an action and the Arduino just has to watch for reports and react to them. In some situations, this may be a good way to reduce lag as well.
Anyway, glad you liked the video! These things are cool, I’m already scheming to make custom MIDI control forms for a bunch of my favorite VSTs. If I ever get around to it, I’ll see about posting a blog post here or a tutorial! And if you do something cool with them, let us know! We’re always looking for cool projects to feature!