Breaking News
Comments
Newest First | Oldest First | Threaded View
<<   <   Page 2 / 2
Max The Magnificent
User Rank
Blogger
Re: Addressing
Max The Magnificent   1/2/2014 3:04:11 PM
NO RATINGS
@David: ...surely too fast for the eye to see [...] very clever


It is way too fast for the eye to see and it's very VERY clever ... also you can have multiple strips -- each cointrolled by it's own Arduino pin...

David Ashton
User Rank
Blogger
Re: Addressing
David Ashton   1/2/2014 3:01:03 PM
NO RATINGS
@Max...some simple math reveals that a 1m string of 60 pixels will be refreshed at 800000 / 24 bits / 60 pixels = 555 Hz - surely too fast for the eye to see.  You'd have to get up to about 50M before you could discern any delay.  Very clever.

Max The Magnificent
User Rank
Blogger
Re: Addressing
Max The Magnificent   1/2/2014 2:53:19 PM
NO RATINGS
@David: Do you know how fast the data is sent?

By some strange quirk of fate I do, because one of the parameters to their function is the clock rate and we checked that on the scope ... it's a 800KHz clock for the data stream to the strip.

David Ashton
User Rank
Blogger
Re: Addressing
David Ashton   1/2/2014 2:44:12 PM
NO RATINGS
@Max, thanks for that, makes perfect sense.  I think you are right about the shift register  analogy - it would seem that you can stream the data to the strip so fast that to the human eye it seems as if you're addressing each pixel.  (ie you could change pixel no 32 without changing the others, and stream the new data, and it will appear as if only that one pixel has changed).  Very clever, I can think of all sorts of effects you could do with these things.

Do you know how fast the data is sent?  (sorry, I'm one of those irritating people who likes to know exactly how everything works....)

Max The Magnificent
User Rank
Blogger
Re: Addressing
Max The Magnificent   1/2/2014 11:15:40 AM
NO RATINGS
@David: Max, you say that each pixel is individually addressable....

Well, perhaps I should have said "Gives the appearance of being..."

Adafruit provide you with an Arduino library, so a lot of the nitty-gritty details are hidden for you.

When you are creating a Sketch that uses these NeoPixels, first you include their library. Next you declare / instantiate a string of these pixels -- let's say we name it "strip" -- using a type of function call. One of the parameters to this call is the number of the digital output pin you are using to drive this string; another parameter specifies the number of pixels in the string (say 60).

One of the things they do for you is to set up an array in memory -- in th ecase of our 60-pixel stribg, you can visualize this as an array  0-to-59 of 24-bit color fields (8-bits each for the red, green, and blue components).

Now you can use one of their functions to set the values assocaited with individual pixels. For example:

    strip.setPixelColor(i, c);

Where 'i' is an integer of variable specifying the number of the pixel in which you are interested (0 to 59, in our case) and 'c' is the 24-bit color value.

Alternatively, you can use:

    strip.setPixelColor(i, r, g, b);

Where 'i' is the number of the pixel in which you are interested and 'r,' 'g,' and 'b' are 8-bit color values specifying the red, green, and blue components of that pixel.

The important thing to note is that using the strip.setPixelColor() function doesn't actually upload values to the physical strip -- it just changes the values in the array stored in your Arduino's memery. When you are ready to update the physical strip, you call the strip.show() function -- this streams (a copy of) all of the values out of the array in memory into the physical strip -- I think the way to think about this is sort of like a shift-register -- as you start shoving data in one end, it gets passed "bucket brigade style" down the strip -- but I'm not sure as to the exact mechanism.


Does this help make things a bit clearer?

 

 

 

Max The Magnificent
User Rank
Blogger
Re: Addressing
Max The Magnificent   1/2/2014 10:41:23 AM
NO RATINGS
@David: Very tasty goodies - as is the power adapter in photo 2.

My chum Brian LaGrave pointed out that you can get these power adapters all over the place, but as I said to him, I'd never seen one before and I was on the Adafruit site after selecting the power supply and I was thinking "I really could do with a ... oooh, look at that!" LOL

Max The Magnificent
User Rank
Blogger
Re: Product placement?
Max The Magnificent   1/2/2014 10:38:59 AM
NO RATINGS
@Phononscattering: I'd like to point out that these so-called "Neopixels" are not a proprietary Adafruit product, but can be bought all over the web.

Very interesting -- thanks for sharing -- I see that you can get 100 of these little rascals as standalones for just $39 from eBay.

David Ashton
User Rank
Blogger
Addressing
David Ashton   1/1/2014 2:42:55 PM
NO RATINGS
Max, you say that each pixel is individually addressable....but looking at your roll of them in the 3rd photo, along with your description of the Data in and Data out signals it seems to me that what happens is that you tell the first LED what colour you want, then when you tell it a different colour, it passes the previous settings on to the next LED, and so on.  Is that what happens?   Can you control the brightness as well as the colour (i'd imagine so....)

Very tasty goodies - as is the power adapter in photo 2.  I recently ordered some SMD mounting boards from Adafruit - had I known they had these I would have ordered a bunch of them as well.  Really handy.

 

Phononscattering
User Rank
Rookie
Product placement?
Phononscattering   1/1/2014 9:22:21 AM
NO RATINGS
I'd like to point out that these so-called "Neopixels" are not a proprietary Adafruit product, but can be bought all over the web. The part name is WS2812 (6 pins) or WS2812B (4 pins) by worldsemi. (www.world-semi.com)
That said, these LEDs are really amazing.

<<   <   Page 2 / 2


EE Life
Frankenstein's Fix, Teardowns, Sideshows, Design Contests, Reader Content & More
Max Maxfield

Oh, No! My Antique Analog Meter Has Twitched Its Last
Max Maxfield
18 comments
Well, life is certainly full of ups and downs, isn't it? When it comes to the antique analog meters I'm using in a number of my hobby projects, things appeared to be going swimmingly well, ...

EDN Staff

11 Summer Vacation Spots for Engineers
EDN Staff
20 comments
This collection of places from technology history, museums, and modern marvels is a roadmap for an engineering adventure that will take you around the world. Here are just a few spots ...

Glen Chenier

Engineers Solve Analog/Digital Problem, Invent Creative Expletives
Glen Chenier
15 comments
- An analog engineer and a digital engineer join forces, use their respective skills, and pull a few bunnies out of a hat to troubleshoot a system with which they are completely ...

Larry Desjardin

Engineers Should Study Finance: 5 Reasons Why
Larry Desjardin
46 comments
I'm a big proponent of engineers learning financial basics. Why? Because engineers are making decisions all the time, in multiple ways. Having a good financial understanding guides these ...

Flash Poll
Top Comments of the Week
Like Us on Facebook
EE Times on Twitter
EE Times Twitter Feed

Datasheets.com Parts Search

185 million searchable parts
(please enter a part number or hit search to begin)