# clarification

Hello,

After buying the Dotstar LED strips for my project (almost done with it), I thought of replicating the same thing using dotstar flexible matrix (the readymade ones for eg which Adafruit sells), primarily because it was quite a hard work!! For the matrices I have a doubt...

If I intend to make a screen using, lets say, 4 dotstar matrices, then when I connect them as follows (assume the 4 quadrants, that would be helpful in visualising and I am placing a matrix in every quadrant starting from 1 to 4. Now I connect the input of 1 to Arduino, the output of 1 to input of 2, the output of 2 to input of 3, the output of 3 to input of 4. My question is: Does this arrangement act like a "Continuous" screen? What I want to know is that is the first row comprised of the first rows of 1 and 2 matrices or the first row is comprised of first two rows of 1 matrix??

Could anybody clarify, because if they are not like first row complete (1 and 2 matrices combined) and so on, the software part would be really tricky to individually address each LED. The numbering would be different.....was just wondering...

Thanks!

Shouldnâ€™t this question be better to ask of Dotstar?

I just wanted to give an example of what type of matrix I was referring, it can be any RGB led flexible matrix (but based on APA102), however the question would still remain the same

bigfatpanda:
I just wanted to give an example of what type of matrix I was referring, it can be any RGB led flexible matrix (but based on APA102), however the question would still remain the same

Software is dependent on hardware used.

It is not one size fits all.

Basically no, chaining four matrix would result in the address of the top line of the second quadrant after the last line of the first quadrant. Unless your library is designed to cope with this then you have to write your own software. Calculating the address of any point on the combined matrix is not difficult however.

Ok thanks for the reply Mike...I did some work on my own and realised something: I know I was stupid to realise this now.... but I have this doubt

So based on what you wrote, I concluded that no matter how you connect or in which shape, at the end, those 4 matrices would be daisy chained (in series), but since my plan is to display a bitmap, this would actually split the bitmap if I were to make a rectangular array....

My doubt: I googled about "parallel" chaining...is it possible with these type of matrices or basically can you parallel AND series chain the APA102 strips....I cant see how you can do it because the strips are linear and continuous meaning that the data line has one input and can only pass along the strip? Am I correct?

And if anybody has hints or guidance on how to parallel chain (if you can), please direct me. Would be really happy....

Thanks!

the strips are linear and continuous meaning that the data line has one input and can only pass along the strip? Am I correct?

That is correct.

But all you need to do is to work out the relationship between a pixel's coordinates and its position along the linear chain. Then you simply translate from the one coordinate system, the want you want to light, to the position in the linear coordinate system, the one you have physically. This is similar the the way you cope with a linear raster as opposed to a serpentine raster in the document I sent you.

@Mike

Yes, I did go through the document you had sent. did get an idea and somehow managed to do it through the coordinate transformation method. Also took help of the XY matrix example given in the FastLED (i guess you had mentioned that too before). Thanks!!!

Another method of displaying bitmap on the display formed using the readymade apa102 matrix was - my total display was 64X32 - I split the bitmap data I obtained into two 32X32 and then passed them separately for the two columns of those flexible matrices. This was more of a shortcut...

Thanks a lot!

wasn't sure of creating a new thread......continuing here only since its the same project.

I am stuck between choosing two options for the project I am working. I did go through related questions on this forum, however getting mixed reviews...

I have a Due and a rectangular area of 65 cm X 35 cm. I do not know which one is better:

1. I cover the area with strips (APA102, 144LEDs/m), on calculating, it comes out to be 2500 LEDs!, Can Due handle this, provided I need a refresh rate for the static images to be displayed within 2-3 seconds? I have the datasheet of APA102, but do not know how to find the time taken to update the whole matrix? Can somebody guide me through a small sample calculation. The construction is a bit cumbersome...soldering..and all.

2. I use eight 832 panels (flexible ones of APA102) and then split the data between two 3232 columns. BUt again the same question. Due handling 2048 LEDs? Refresh rate needs to be high.....the updte should take max 3 seconds for every image. The construction is much cleaner here.

I can work with both, software part if ready. But which one is better and how to find the update times for each image for the LEDs? Also, in the first case, I guess, I would need to ground all strips together and require multiple powering for every 200 LEDs or so (I read somewhere)? The space is a constraint.

@Mike..Referring to your reply on this http://forum.arduino.cc/index.php?topic=50668.0 , I have 1000 LEds less....hoping mine should work.

Any help in choosing one would be nice. Both seem appealing however I am sure i cant see something that experts can. Please let me know.

Thanks!