Hi all im looking for a little advice, I have a project that i want to do which has 500 pixels, I would like to use Ws2801 as i have used these before and an arduino Pro mini (so an Atmel328) the px would all be in a single string, can anyone see any issues with this? i work out that 500px will need a buffer of 1500bytes (3x 500) the 328 has 2kb of sdram so i think this should be ok?, im a little unsure how to work out what kind of frame rate i could achieve, my pattern is rather simple so i could go as low as 15fps.
Hi!
I’d recommend going with a board with more RAM. While your math (3 x 500 = 1500 bytes; 1500 < 2048) is correct, it’s worth keeping in mind other things that also use up RAM: global variables (yours and Arduino’s), the call stack, and local variables.
I’ve successfully run 400 pixels from a ATmega 328, but 500 seems awfully tight. You could try!
For more RAM at a very modest price, I really like the Teensy 3.0 and Teensy 3.1. They’re also much faster ARM processors, and even though you said that’s not an issue for you, they do also re-program VERY quickly, which makes development and testing much less of a pain.
If you want 16 FPS, for 500 pixels, that’s 16 frames/sec x 500pixels/frame = 8000 pixels/sec … Easily within the speed envelope for WS2801! (Someone cross-check my math here?)
I’ve done 576 pixels on a Yún (which has a Leonardo-like 32u4, with 2560 bytes of RAM.) It’s tight. With some patterns, random things just fail and you’ve no idea why or what, until you think “maybe it’s RAM-related” and try cutting down your RAM usage and then it works ok.
Definitely go for the Teensy. It’s no “harder” than a regular Arduino.
Hi (Toulouse Bot here , was logged in with the wrong gmail account).
thanks for the comments, i have done a little revision to the plan and seams it will end up being around 380px so 400 max,
going from Marks comments im thinking i will stay with the 328 to begin with and get a teensy in stock just incase. main reason i want to go with the mini pro is that i need 3 button inputs and i have already (from a previous job) created and had built my own custom breakout (with Opto and EMI protected inputs, connectors and a nice case.) so the physical build would be minimal