I asked these questions in an email to PJRC, and in place of actual customer service, was told to post them here, where they (Paul?) would answer them. Still nothing. So...I'll start answering them myself. (oh, tonton81, what LCD? Just what I said. The "colour LCD touchscreen". I believe PJRC only sells one of those. Need a link?)
Q: What will I see looking into the LCD LED pin? Direct white LED connection?
The web page so helpfully says,"Use 100 ohm resistor". To what? Oh...Teensy VIN I guess. Hmm. Helpful.
A: Yes, 3V LED.
Looking at the back of the PCB, there appears to be just one LED. From the front, maybe 2 or 4 (in parallel). Doesn't matter much. Here are voltages & currents (actual specs...hallelujah), comma-delimited for your importing pleasure:
V, I(mA)
2.7,4
2.8,13
2.9,22
3.0,30
3.1,39
3.2,50
3.3,60
3.4,73
3.5,83
3.6,96
3.7,107
3.8,122
3.9,135
I wouldn't suggest a direct 3.3V connection, tempting though it may be.
Without knowing more about the LCD module, it's hard to make any recommendations. I'll probably try running ~50mA, which would take 36Ω to 5V. Though, as per one of my other questions, I think the LCD can run at 3.3V with a regulator bypass, in which case a 2Ω(!) resistor to 3.3V will add some small safety margin. Hmm.
I don't know what PJRC's problem is. The website sucks, navigationally, and informationally. It's out of date too. I've seen better specs on Chinese sites!
Oh well, if they go out of business, there are other companies doing similar products...
p.s., The "DemoSauce" code is running on my 3.2/LCD as I type. I'm truly impressed at what's possible over a serial link. Wow. Even though my first project doesn't require any real display "bandwidth", I'm really glad to see it's there!
p.p.s., Couldn't get the UTFT demo to even compile... :-( (even after DLing UTFT!)