Build Your Own SLA/SLS

Anyone has a connection block diagram between the laptop, arduino board and the projector?
Do I need a USB to RS232 cable?

The laptop connects directly to the arduino via usb cable.
The laptop connect directly to the projector via vga / dvi / hdmi or similar.
If you want to try and use the projector serial port you would need a laptop with a serial port, or a usb->serial converter.

Thanks. Would using the HDMI from the laptop to the projector improve the print quality compared DVI or VGA?

HDMI and DVI are both digital, so either the image will come through, or it won't.

VGA is analog, which could be considered noisier... but it's what I use. I feel like you're more likely to have print quality change on account of resin variance, vat freshness, and print structure than through the cable's signal.

Here is a comparison I did comparing VGA vs. HDMI using the exact same settings. The HDMI is much 'clearer'.

Fantastic thanks.

PomperoyB,
Actually, I could not get any better results with the VGA other than the one shown in the picture. It was setup for VGA originally (which is what I had been using for months) but decided to try HDMI on another laptop using the same settings (SubG+, 100umXYZ, 14 sec exposure, FEP flex vat). Attached is the drawing for the sample file and the CW layer photo output (the 0.5mm post is only about 4 pixels wide).
Disclaimer: this was just my unscientific test to show VGA vs. HDMI on my 100um mUVe printer not LittleRP.
EDIT: Did some research because I just wanted to understand better the difference between analog and digital signals. Long story short, VGA has to go from digital (computer) to analog (cable) and back to digital (projector) and the conversions can effect crispiness. Many comparisons out there where people had two identical monitors run off same computer, one vga, one hdmi, and there is a difference (slight) between the two. I don't claim to be an expert.