@Daniel_Garcia Question about (ab)using the four hardware SPI output on the Teensy 3.* with APA102 strips hack–
Does it matter if the Data and Clock lines are split before or after going through the level shifter?
Just realized I have my wire pairs incorrectly drawn there, but in any case… does it matter if they are split before or after?
Should be:
FastLED.addLeds<APA102,7,13>(leds[0],NUM_LEDS);
FastLED.addLeds<APA102,7,14>(leds[1],NUM_LEDS);
FastLED.addLeds<APA102,11,13>(leds[2],NUM_LEDS);
FastLED.addLeds<APA102,11,14>(leds[3],NUM_LEDS);
[ from wiki page: https://github.com/FastLED/FastLED/wiki/SPI-Hardware-or-Bit-banging ]
When I’ve done this, I split them after the level shifter and it worked well. This is also how it’s done if you use the OctoWS2811 adapter.
Thank you for the info @Jeremy_Spencer . Btw, how many leds we you driving when you used this? Any other tips related to this?
I was only driving about 100, but this seemed to be the best way to drive them. They’re in car headlights, strips and halos each side and it helps with reliability to drive them as four sections. Here’s a video, they worked out quite well https://youtu.be/IMoTzYXUi68
Nice work. And good point about how this splits things up for reliability. I hadn’t even thought of that until now.
If you have the spare gates in the level shifter, you may as well use them as in option B. Any spare inputs have to be tied to something, else floating inputs can cause a CMOS chip to draw excess current.
If you do use option A with longish wires to the strips, then you should have separate impedance matching resistors (e.g. 100R) on each wire.
Also check out “fan-out” which becomes important if you try to scale this up significantly.
I’m a bad one to ask on this - I don’t level shift when driving APA102’s 
Hehe ok, thank you Daniel.
@Kean_Maizels Interesting, I did not know that about spare (floating) inputs on a level shifter. I guess that would be more important with battery powered projects for power saving? Could spare inputs just be connected to GND through a 10K resistor?
Since the 74HCT245 has 8 inputs might as well try using vers B then.
[Corrected wiring paths]
missing/deleted image from Google+
@marmil it is not just a problem on battery power. If you leave inputs on many CMOS ICs floating, it can actually cause erratic behaviour[1]. A pull up or down is the recommended solution, but spare inputs can be connected to any valid logic level, such as GND/Vss, Vdd, or just a neighbouring signal.
Thank you Kean. Appreciate your knowledge.
If you fan-out before the level shifter, the shifter will be able to drive longer lines (it can source or sink only so much current per pin). I had this bite me on the ass with a Burning Man project a couple of years back.
Thank you @Luminous_Elements Can you give a bit more insight in what worked/didn’t work? Was the level shifter close to your controller, or far way and near the start of the leds? What length of data lines were you working with?