Glow poi using Gemma v2 and Flora NeoPixel v2

Projects General Guidance
1

I am looking to create a pair of glow poi similar to those sold here. Each one will have an Adafruit GEMMA v2, two Flora RGB Smart NeoPixels (v2), and a 150 mAh 3.7V Lipoly battery housed in a semi-opaque, soft plastic, spherical casing. The NeoPixels will be placed back-to-back in the center so that each one illuminates one half of the sphere. For those of you who don't know, poi are flung around on strings so they will have to be durable and have the internal electronics well protected.

I am hoping to have a flat access panel on each one which will have an on/off switch, a mode-selection button, a USB port (for recharging and reprogramming), and a sturdy metal or hard-plastic loop to tie the string to. So far, I only have the GEMMAs and the NeoPixels. Attached is a picture of what I have set up.

So far, I have been able to control both NeoPixels independently and haven't noticed any problems. My questions are (in order of concern):

  • Is it necessary to put capacitors on the Vout and ground lines between the controller and the first pixel? What about a resistor on the data line? Keep in mind that the final setup will likely have much shorter distances between each of the components as it will all need to fit into a small package. Also, I would like to point out that while I am planning on using a 3.7V battery in the end, I will be powering it using USB while I am testing/developing.
  • Does giving power to the USB port charge the battery? Does the on/off switch built into the GEMMA affect this at all? I would like to have an external on/off switch which controls the power but allows charging in both modes.
  • Is it possible to keep the boot-loader from running when power-cycling, but only have it run when the reset button is pressed?
  • Does the GEMMA have any ability to turn itself off so I can program in a battery-saving function?

Thanks in advance.

flora_setup.jpg
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I've never bothered with the resistors in the data lines. I think you do need it for long distances or something, but it seems fine without it at short distance. I just about never see them in WS2812B arrays.

Those neopixel boards include the 0.1uf cap between power and ground. You ought to have a larger cap at the start of the string.

The PWM of Neopixels is kinda slow - is it fast enough for your application? I thought poi you swung around and the lights looked cool. The slow PWM would result in it leaving a dashed-line of color in an observer's field of vision if it's moving fast enough and one or more colors aren't on 100% or 0% (persistence of vision effect). Or is that desirable? If that turns out to be a problem, do not despair - use an APA102/"Dotstar" LED instead; they have much higher frequency PWM (20khz iirc)