hello, I need to drive a 48x96 px arrays of APA102 and I would

Antoine_Villeret · October 23, 2014, 9:53am

hello,

I need to drive a 48x96 px arrays of APA102 and I would like to know what is the best device to do so.
The whole array take 18kB of memory so if I use an Arduino, I’ll need a Due (because of sRAM amount).
But what about update rate ?
I guess I can put about 300 leds on one bus, could I drive 16 bus with a single Due ? Or how many boards would I need to drive 4608 pixels ?
Or which board would you recommend to me ?

thanks for helping

hans_cromheecke · October 23, 2014, 9:55am

use a teensy 3.1

Antoine_Villeret · October 23, 2014, 10:10am

thanks for the quick answer.
Are you saying that it won’t work with a Due ?
It has a 32bit processor, quicker than Teensy 3.1.
I need an ArtNet server to control the array so I was thinking about using an Arduino with an Ethernet shield, because it seems to me to be easier than the Teensy 3.1 + WIZ112 Ethernet module.

PaulStoffregen · October 23, 2014, 11:47am

For Ethernet driving 4600 LEDs, definitely avoid the W5100 chip (the one on the normal Arduino Ethernet shield). It’s got a ton of SPI overhead. Every byte of data takes at least 4 bytes on the SPI bus. The W5200 has a much more efficient burst access mode, so you can get most of the SPI bandwidth. Luckily, Artnet uses UDP, and the W5200 is pretty efficient when reading the whole packet into memory at once.

Unfortunately, you’ll have a hard time making this project work (at fast update speed) with a SPI port shared between the Ethernet and the LED output. Ideally, you want 2 different ports to bring the data in and also stream it out, hopefully simultaneously.

Here’s a project I made several months ago for Freescale at Maker Faire, with 4320 LEDs, updating with 30 Hz video.

An updated version of that code is available here:

github.com

PaulStoffregen/OctoWS2811/blob/master/examples/VideoSDcard/VideoSDcard.ino

/*  OctoWS2811 VideoSDcard.ino - Video on LEDs, played from SD Card
    http://www.pjrc.com/teensy/td_libs_OctoWS2811.html
    Copyright (c) 2014 Paul Stoffregen, PJRC.COM, LLC

    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
    in the Software without restriction, including without limitation the rights
    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    copies of the Software, and to permit persons to whom the Software is
    furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be included in
    all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

This file has been truncated. show original

Updating this many LEDs at 30 Hz or faster is quite a challenge.

Antoine_Villeret · October 23, 2014, 12:17pm

thanks for the feedback,
what a nice panel you did !
I need something like this, but flexible
I’m not married with Arduino at all, I can use anything else, I’m just looking to the easier in the price/time balance
I understand the SPI port sharing issue, and I guess I will have the same with the Teensy since there is only one SPI bus on it.
So I’ll take a look at Raspberry Pi on which the Ethernet port is shared with USB and not with SPI.
But FastLed doesn’t easily work on it, isn’t it ?

Robert_Atkins · October 23, 2014, 12:23pm

FastLED doesn’t run on the Pi. But depending on how soon you need to build your display, @Daniel_Garcia did mention he was interested in supporting the Beaglebone (it has PRUs—Programmable Realtime Units—that you could port FastLED to.)

Antoine_Villeret · October 23, 2014, 5:50pm

nice to hear that FastLed will increase supported platforms !
but I need to make some tests really fast, and I think I will go with PixelPusher board.

hans_cromheecke · October 23, 2014, 7:20pm

pixelpusher is based on teensy , and is not bad at all