@MichaelMeissner, I had two teensy 3.2's arrive today so I'm looking to make it work with them. I mentioned the adafruit projects more to get an idea of the brightness at 3.7v, which I assumed they were running at, although im not sure if they both are anymore. Both projects use the 5v version, the poi use the 5v trinket and the staffs the 5v trinket pro. Both are powered with a 3.7v battery but the trinket pro has:
•On-board 5.0V power regulator with 150mA output
Does this mean it has a level converter built in?
Gonna take another look at the apa's datasheet.
Bear in mind I am a software guy, but the regulators on the Trinkets appear to be buck regulators that take voltages up to 16v and drop the voltage to 5v or 3.3v respectively. If you are powering the chip with 3.7v, and it is the 5v version, you are underclocking the part. Now in general AVR's tend to be forgiving on voltages, so running it under spec may work. I would anticipate that running neopixels/ws2812's might be more problematical than dotstars/apa102's, since the neopixel has a very strict timing window, and if you are running the board underclocked, the timing might not be correct. This is just speculation on my part, I have never run any of the boards at voltages under the limit.
Let me try to be clearer about when you need voltage shifting. Note, I have used neopixels/ws2812's a bit, but I haven't used dotstars/apa102's, but this is from reading the datasheet and my experience with ws2812's:
If you are running off of a 5v supply (like USB), and you are using a 5v processor, then you don't need a level shifter. You want to connect the power input directly to the lights, and not use the 5v regulated pin on the processor. This assumes the voltage is regulated to 5v like USB power is.
If you are running off of a 5v supply, and you are using a 3.3v processor, assuming you connect the 5v power to the leds, then you likely need a level shifter going from 3.3v to 5v. You might be able to get away without using a level shifter, but the datasheet says that the data signal must be at least 0.7 times the power signal, which is 3.5v. Maybe it will work, and maybe it won't. Some of my neopixels will work with this setup, some won't (mostly the newer ones when they changed to a new process are stricter about voltage).
If you are running off of a power supply that is above 5.5v on the trinket, you run the risk of damaging the leds if you run the power straight to the LEDs. If you use the 5v power pin to power the LEDs, you need to make sure that the total power that is used by the LEDs is less than the design limits for the processor you are using.
Note, if you are running off of a power supply that is more than 5.5v (for Teensy 3.0/3.1/LC) or 6v (for Teensy 3.2), you likely just fried your Teensy (and your LEDs if you connected the power to them).
If you are running off of a 3.7v power supply to a 3.3v processor, you don't need a level shifter, assuming the LEDs can run at 3.7v. The current generation of neopixels' datasheet says that the LEDs will work at 3.5-5.5v. The APA102 datasheet says 5.5v is the max, but it does not list a minimum. So whether APA102's will work at 3.7v, might be an issue. The LEDs will likely be lower intensity at 3.7v than at 5v.
If you only have a 3.7v battery, and you are running 5v processor, you may need an external boost circuit to bring the power up to 5v. If you are running a lot of lights, you need to figure out whether the battery and the boost circuit can handle the load. Note, a lot of boost circuits can get very hot.
Basically, according to the datasheet, APA102's are happiest when fed 5v power, and the data signal is 3.5v-5v.
I have burned out a Digispark (similar to a plain 5v Trinket, but the regulator is a lot less robust) by using the 5v regulated power pin, and not the USB input power pin.