Hey guys
Just wondering if this is me or something with the Arduino. I have connected 5 strips of 5m of APA102 together (30 leds/m), so in total I have 750 LEDs. I have my program running fine for 600 LEDs, however when i change it so that it has 750 it does not work. Is there a limit to how many LEDs the Arduino Uno can handle? If so, is there some other device I should use, any suggestions? Or that aside, is there a common problem I am overlooking?
The UNO has 2kb of ram (2048 bytes). Each pixel takes 3 bytes of ram - so 600 LEDs is using 1800 bytes of ram and 750 LEDs is using 2250 - aka more than you have which causes things to not work.
Time to start looking into the Teensy 3.2, along with an OctoWS2811 in order to convert the 3.3V output to the 5V required by APA102’s.
ah ok. Thanks you guys. Kind of brings me onto a second question. I got a t4000 (http://www.ledlightinghut.com/t4000-4-ports-led-sd-card-controller.html) with my lights (which i guess i now need to use), any recommendations on what software to run it with if it is not possible to do so via FastLed?
Not I, i’ve never used it.
@Tejkaran_Samra
Your link includes info about a “LED editor software” I guess that is what you would need to program animations in that t4000.
I would also highly recommend the Teensy but if it is easier for you you could go for an Arduino MEGA or Due that has sufficient ram for your 750 RGB LEDs.
So how many LEDs can a Teensy do, and how much for the MEGA/Due, because i anticipate i will be doing much more in the future, if possible.
and thank you
Honestly, with the teensy you’re likely to run into cpu
limitations first.
The teensy 3.2 has 64k of ram, or enough for over 20,000 pixels. While the mega has 8kb of ram.
But there’s more to the question of “how many LEDs can I run” than just memory.
For example, with the ws2811, it takes 30us to write out the data for one led. So, it would take 30ms to write out the data for 1000 LEDs. Or, to put another way, you could do a total of 33,000 pixel updates per second - or, with the aforementioned 20,000 pixels, 1.5 frames per second 
Other led chipsets are faster, but then there’s the question of how long your programming takes to compute a frame.
The question of “how many LEDs” is a complex one that depends on the type of led, the kind of frame rate that you want, and what you are doing per frame.
thank you @Daniel_Garcia et al.
I’ve invested in some Teensy’s now. I like the fact I cans tick with FastLed now too. whoop. Although, on the bad side for you it means I will probably end up asking you some more questions!
here’s a little posting I made on asking for help at http://tuline.com/getting-fastled-help/
@Daniel_Garcia , just double checking, the apa102 data sheet shows each led frame needs 32 bits or 4 bytes. Above you state that each apa102 pixel needs 3 bytes. I’m hoping you know something that isn’t stated in the data sheet.
I’m talking about bytes in ram - the apa102 has an extra 8-bits of control information sent before the 24-bits of rgb data - this is generated on the fly, no reason to store it in memory.
+Daniel, to be clear I’m not talking about the control information at the beginning. I’m asking about the other 8 bits that are part of each ‘32 bit LED frame’. I’m guessing it’s the brightness data?
Neither am I - i’m talking about the 8-bits of data at the beginning of each pixel - 3 bits of header, 5 bits of brightness.
Again - the CRGB object is 3 bytes per led pixel - and has no relation to what gets written out (the APA102 isn’t the first led chipset to want 4 bytes of data written for each pixel - the P9813 sends a CRC byte - and another chipset out there actually sends 25-bits per pixel (3 bytes, plus one flag bit at the beginning).
@Daniel_Garcia I was hoping that would be your answer. It allows me to cut my storage by 25%. Thank you for clarifying. Also, is there a decent document for the APA102 implementation? The data sheet is pretty sparse.
Not officially - this might be the closest thing - https://cpldcpu.wordpress.com/2014/08/27/apa102/ - those data sheets are pretty much all I usually have to work with
Ya, that appears to be the best out there right now. Again, thank you.