2019/04/01
SmartMatrix, SmartMatrix Shield v4 for Teensy, ESP32 shield with level shifter, and SmartMatrix::GFX
π
2019-04-01 01:01
in Arduino
Less blah-blah, more code
Sure, there you go: https://github.com/marcmerlin/SmartMatrix_GFXWhat is it?
https://github.com/marcmerlin/SmartMatrix_GFX is a zero copy, zero extra buffer frontend to Smartmatrix, which is the best arduino API driver for RGB Panels.It supports these 4 APIs seemlessly and concurrently in the same code:
Give me Examples
Sure: https://github.com/marcmerlin/FastLED_NeoMatrix_SmartMatrix_LEDMatrix_GFX_Demos This page that shows how I built my EDM Festival and Burning Man LED Pants and Shirt v4 on ESP32 with RGBPanels and SmartMatrix::GFX using this library.More blah-blah & rationale for SmartMatrix::GFX
Last year, I wrote FastLED::NeoMatrix to let me run Neopixel Matrices made out of pre-made panels arranged as a bigger panel. This was the end result: http://marc.merlins.org/perso/arduino/post_2018-04-23_FastLED_NeoMatrix-library_-how-to-do-Matrices-with-FastLED-and-Adafruit_GFX.html This allowed me to do my Party shirt v3 based on a NeoPixel Matrix However, the main problem I had was the limited pixel density of those neopixels and the price per pixel given that each pixel has a very small computer chip attached. My shirt was only 768 pixels per side (32x8x3) which cost $80 per side. While my shirt looked cool (i.e. better than nothing), 32x24 resolution isn't that much to display cool stuff. I made the best of it, but I knew that I wanted more pixels.While it's technically possible to get 0.5cm pitch (i.e. P5) with nepixels, there is no such panel I could buy today and I wasn't really interested in fabbing my own, so I switched to RGBPanels. What allowed me to switch were those flexible P4 RGB Panels from Azerone: https://amazon.com/gp/product/B07F87CM6Y RGBPanels are a totally different technology based on row scan technology, pretty much like the 8x8 matrices I wrote a scanning driver for but with a built in shift register to load up all the column for each color, multiplied by 2 as for historical reasons you can update 2 halves of the panel separately.
With 32x64 panels, or even 64x64 panels, that's a lot of pixels to push serially via shift registers and address lines to select the line you've currently pushed all those columns for. The LEDs need to be refreshed very quickly to avoid visible flickering.
This limits the list of reasonble CPUs for higher resolutions to teensy 3.6 and ESP32, which also removes the multiple slower and/of inefficient drivers out there. Options I looked at and weren't suitable:
The goal was for me to be able to re-use that code and make it work on both FastLED backends and SmartMatrix backends, which why I wrote SmartMatrix::GFX
https://github.com/marcmerlin/SmartMatrix_GFX offers a GFX compat layer that is virtually identical to my FastLED::NeoMatrix library and allows you to run the same code onto of either FastLED or SmartMatrix supported panels.
Hardware, Teensy 3.6 and SmartMatrix Shield v4
The easiest way to use SmartMatrix is to use the SmartMatrix Shield v4 from Louis Beaudoin.If you are going to drive 64x64 and above, skip the teensy 3.0/3.1/3.2 and go directly to teensy 3.6. It costs more, but you'll want the extra CPU speed (teensy 3.1 can barely run 64x64 with an ok-ish refresh if you overclock it, if you must use the older chip). Here is what the SmartMatrix shield looks like with a small patch I made to take USB power and send it to the panel (my laptop can output 2A over USB). Note that this is not safe with teensy v3.1/3.2 as it's not meant to pass that much current from its USB connection, but teensy 3.6 can do it fine as its fuse is located after the V+ connection on the chip:
Originally I used the APA connector to send power to the panel
2x 32x64 chained P4 panels with a sad cable extension I had to make, vs pre-made 64x64 P3 panel
Hardware: ESP32
As mentioned above, ESP32 is dual core, so it can update the panel on one core using DMA, while the other core can run your code. It is more efficient, however, it runs out of DMA memory around 64x128 resolution (I run 64x96 myself and had to optimize code to make things fit).. Here are shots of what it looks like with Jason's shield:
it's reasonably compact, 15 IO's for SmartMatrix (14 are really required), IR connected to port 34, and IO 16 connected to a NeoPixel strip
Louis Beaudoin added ESP32 support in this branch https://github.com/pixelmatix/SmartMatrix/tree/teensylc .
You'll want to look at this file for how to wire your ESP32: https://github.com/pixelmatix/SmartMatrix/blob/teensylc/src/MatrixHardware_ESP32_V0.h#L62
While you can apparently get away with no using a level shifter (at least with some panels), I chose to use one. First, I did it the hard way with a protoboard and level shifter chips, and then I switched to Jason Coon's 16 output ESP32 shield.
I then used a HUB75 ribbon, cut the end, and made a straight connector that went directly into the IO pins coming fromthat shield Here are pictures of what it looks like: Hopefully in the near future, one will be able to buy a pre-made ESP32 SmartMatrix shield.