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Author Topic: DotStar - New, faster neopixel stripes on the horizon ?  (Read 2440 times)

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Offline Obi_1

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Adafruit just came out with new, faster neopixel stripes called Dot Star

I made in the mean time a bit of a research. The LED driver is based on the APA102 chip, which is SPI based. Adafruit API does not look very complicated and the Stardust has the SPI pins I need (by sheer luck :) ), but software SPI would also be possible.

Brightness-wise the specs look slightly lower in the mcd ratings compared to the WS2812B or SK6812, but before the actual tests I would be reluctant to overrate the importance of mcd. Considering that in segmented LED blades I used to put 100 ultrabright straw hat LED which had mcd ratings ten times the rating for neopixels (10k to 18k mcd), brightness is not a linear function of mcd.

On the bright side, the new protocol is fast enough for AniBlade effects (sort for Animated Blade like the fire blade or the unstable blade effect I'm experimenting with, which goes beyond mere iginition/retraction/shimmering).

As soon as my first segment arrives and I integrate the API, I will update you about the results. I will also measure the idle/off-mode current, it is not in the spec but is an important parameter.

Adafruit DotStar Digital LED Strip - Black 144 LED/m - One Meter ID:

Offline erv

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Just came out? Not sure what you mean, i've been using dot star strip since like 2015 (ish)  :question:

Offline Sethski

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Interested and look forward to hearing/seeing more about 'Aniblade effects'.

I guess whether or not it's been around for a bit, it sounds good to me if it inspires and enables and leads to availability of some pleasing new saber effects :smiley:

To put it in terms of what might be more tangible for many people, any idea what the effective 'frames per second' rate be for WS2812B/SK6812 and for Dotstar if using, say, a 120 LED strip? Thanks.

Offline erv

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a neopixel or alike takes 3.5ms to refresh a 120 pixel strip (on my boards at least). That's 285 fps while the eye can deal with 30-60.
The APA102 or alike can have a faster refresh rate but overall they are mostly used because you can refresh the strip at the rate you want, with less time constraint.

Driving a neopixel strip leads to more intricate programming if you want it to have no impact on the latency of your board, and I've see one board so far using it "by default", simply because the dev couldn't deal with both sound and refreshing the neopixel, which is super CPU intensive if you handle it "the simple way". As pointed by adafruit, neopixels can feature a maximum of 400 Hz fps which is not suitable for PoV systems (which a saber isn't, even if the Profezzor'n demoed it's clearly possible) and are usually used on large number of pixels (I have friends in performance arts refreshing thousands of leds at once at high FPS).
In the same idea, neopixels would be very limited to display video for instance, as soon as the res increases, your refresh rate would drop on 1/X^2 which is quickly catastrophic (same for PoV) reason for increasing the pixel refresh rate like the dotstar proposes.

I've experimented with the first generation of dotstar strips, they "work" without a doubt. But I'm just happy with my zero-CPU neopixel driver, I like the simplicity of it, then it uses only one data wire which is also helpful for the connector system. Dotstars also have more burn-out along the strip (1 additional data wire on the same width leads to less copper density, or maybe it's just the manufacturing). This last point is less of a concern on a 90cm strip though.

Offline profezzorn

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Dotstar pixels have one more adavantage: higher color resolution. This mostly matters for dim colors though. (Like if you want a slowly pulsing accent led, dotstar pixels might be better.)
Probably the biggest problem with dotstar pixels is the lack of choices. There are no through-hole or slim dotstar strips.
While POV stuff is kind of cool, it's just not worth the extra hassle in my opinion. TeenySaber does have experimental dotstar support, but I don't know if anybody has actually used it.


Offline erv

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While POV stuff is kind of cool, it's just not worth the extra hassle in my opinion.

Seconded. I only mentioned it as credit to your PoV blade !

Offline jbkuma

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What's really worth the hassle? Many of us spend days if not weeks perfecting minor details that nobody else would notice!

Offline Obi_1

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Please indulge a passionate tinkerer. I will still give it a try. If I had listened to naysayers back in 2015, the Neopixel blade would not exist.

Offline JakeSoft

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Please indulge a passionate tinkerer. I will still give it a try. If I had listened to naysayers back in 2015, the Neopixel blade would not exist.

Go get 'um, Obi_1!