gemma starter kit not working with neopixels

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drewp2000
 
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gemma starter kit not working with neopixels

Post by drewp2000 »

I got the gwmma starter kit and tried the blink sketch and it worked so tried the strand test for neopixels and when its plugged into usb the neopixel light up pure white uploaded the strand test it said successful yet when plugged in to battery nothing lights up when testing on usb other than white it will not cycle colors only testing on 1 neopixel at the moment

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Franklin97355
 
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Re: gemma starter kit not working with neopixels

Post by Franklin97355 »

Could you post clear pictures of both sides of your board showing any soldering you have done and the connections to it?
Did you modify the strandtest for the number of pixels you are using?

drewp2000
 
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Re: gemma starter kit not working with neopixels

Post by drewp2000 »

1410464212131-1.jpg
1410464212131-1.jpg (81.12 KiB) Viewed 539 times
Yes i changed the strand length to 1 and the pin to 1 it will light up white the instant it is plugged in to usb but will not cycle color or work with battery at all

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michaelmeissner
 
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Re: gemma starter kit not working with neopixels

Post by michaelmeissner »

The Gemma is a 3.3v processor, and you are feeding 5v to it via USB. While the Gemma can handle conversion of 5v to 3.3v used internally, the data signal from the Gemma will only be 3.3v. The neopixel's main power is coming from Vout, which in this case is 5v. Some neopixels will not recognize a 3.3v data signal when powered with 5v (and some will) because it is looking for something close to the voltage that powers the neopixels as the on condition. My 24 LED neopixel ring for instance will not work in this situation, the older 16 LED rings that I have do work fine. I believe it is out of spec, and it is just a matter of luck of the draw whether the neopixel will work in this case.

If instead of powering the Gemma with a 5v source like USB, you power it with a 3.7v source like the lithium ion (li-po/li-poly) batteries that Adafruit sells (https://www.adafruit.com/products/2011), it should work. The neopixels will get 3.7-4.2v of power, and 3.3v signals. Unfortunately this means after programming the Gemma, you have to unplug it from the USB and plug in the lithium io battery.

Alternatively, if you are going to power stuff with 5v all of the time, the 5v trinket is perhaps better suited to powering neopixels than a 3.3v Gemma or 3.3v trinket.

There are ways to level shift the data signal from 3.3v to 5v for neopixel, but this can get complicated, due to the fact that the neopixel has a tight timing window, and you need a level shifter that is fast enough.

drewp2000
 
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Re: gemma starter kit not working with neopixels

Post by drewp2000 »

thanks for the very long explanation about voltage is an input and output voltages that I am aware of but if you would have read the first post that states it does not even work on a 3.6 to 3.7 battery plugged into the connection onboard the whole its not lighting because of wrong volage is not possible as the 2 battery connector that comes with the kit outputs 3.7 volts on brand new batteries.

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Franklin97355
 
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Re: gemma starter kit not working with neopixels

Post by Franklin97355 »

Could you show us the connections to the pixels and the gemma?

drewp2000
 
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Re: gemma starter kit not working with neopixels

Post by drewp2000 »

after hours of frustration the issue finally resolved the code was not being loaded from code bender even though it said it was had to fix bootloader timing with code bender

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Franklin97355
 
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Re: gemma starter kit not working with neopixels

Post by Franklin97355 »

had to fix bootloader timing with code bender
Could you let us know what you had to do so others with the same problem can learn from your experience? Thank you for persevering

drewp2000
 
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Re: gemma starter kit not working with neopixels

Post by drewp2000 »

no matter how many times I tried loading a sketch it said it was uploaded successfully but failed every time even when pushing the reset button and putting it back into it bootloader mode finally I figured out in order for it to work with code bender on the web in the bootloader you have to unplug the USB from the computer plug in and immediately hit upload from the web otherwise the timeout is too short a timeand even though it set up load was successful it was only successful one out of every four times when I did that otherwise it would just a successful when it didn't actually load onto gemma

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