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Random (non-strip based) dotstars
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Random (non-strip based) dotstars

by JonHylands on Sun Dec 05, 2021 10:34 am

I am building an RC rock crawler, and I am putting in an onboard microcontroller (ESP-32). One of the jobs of this microcontroller is to control the lighting of the vehicle, which will include things like light bars (basically mini-strips), plus a bunch of individual LEDs in various places. I plan on creating small surface mount PCBs anywhere I will mount one of these LEDs, and building my own strips using (again) custom PCBs with surface mount LEDs (I have a reflow oven, and do lots of surface mount work).

So the question is, can I use dotstars (APA102) LEDs for this purpose? I plan on using a mix of white and RGB LEDs (white for the main light bar, RGB for most of the discrete ones, etc). Do I have to daisy chain the whole set of LEDs together, so it effectively forms one long strip? How do you address an individual LED - is it just its position on this long strip? How does that work internally?

I have used bus-driven servos before (like the AX-12) - each one has a microcontroller, and each one has its own ID, which means the bus topology is irrelevant, other than every servo needs to be connected to the bus. It appears these LEDs are not like that, but I can't find any references to how they actually work - the examples given are always for linear strips.

- Jon

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Re: Random (non-strip based) dotstars

by dastels on Sun Dec 05, 2021 6:32 pm

If you have a number of DotStar or NeoPixels connected together they logically are a single strip. Address is by position in the strip.

See https://learn.adafruit.com/adafruit-dotstar-leds as well as https://learn.adafruit.com/adafruit-neopixel-uberguide for backgrouns as NeoPixels are very similar to DotStars.

Dave

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Re: Random (non-strip based) dotstars

by JonHylands on Sun Dec 05, 2021 6:36 pm

Okay, thanks - I'll have to make sure I wire them that way.

- Jon

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Re: Random (non-strip based) dotstars

by dastels on Sun Dec 05, 2021 6:58 pm

Just pay attention to the Clock/Data-in and Clock/Data-out. Power and ground are in parallel but data and clock are in series.

Dave

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Please be positive and constructive with your questions and comments.