Project Details

SmartLED Shield enables the Teensy 4 to drive high-quality graphics to HUB75 RGB LED panels, with 36-bit color and 240 Hz refresh rate across large panels (e.g. 128x64 pixels). A Teensy 4.0 or Teensy 4.1 with pins fits into the socket on the shield, and the shield can attach directly to the HUB75 panel or through a ribbon cable. The SmartMatrix library for Arduino makes it easy to draw basic graphics, create scrolling and static text, draw beautiful patterns using FastLED, and play animated GIFs on the panel. Example code is provided so you can get started as quickly as possible. The Shield and library use special features and peripherals of the Teensy 4 processor to send graphics data to your display with minimal CPU usage, so you can use the processor to do other tasks in parallel such as SPI communication, file decoding, or complex rendering.

Using SmartLED Shield with SmartMatrix library and the Teensy 4 is the easiest way to drive high-quality and high pixel count graphics to RGB LED panels with a microcontroller. Use a simple API to tell the library what to draw on the screen, and the library takes care of refreshing in the background. Advanced features like these are enabled automatically:

• 36-bit Color Refresh - See the full color range in the image or pattern you're displaying, with no noticeable brightness steps when dimming pixels down to black. Up to 48-bit color refresh is available.
• Color (Gamma) Correction - Your source graphics are probably 24-bit color, but SmartMatrix library applies automatic color correction so they have good contrast, smooth gradients, and don't look washed out.
• Global Brightness Control - When you don't need the full brightness of the LED panel, lower the brightness without having to sacrifice color depth of your graphics.

The shield is easy to assemble and connect to a panel, and there’s no soldering required beyond adding pins to the Teensy. The Teensy is removable, so you can swap between the 4.0 and 4.1 if you want. All long edge Teensy signals are brought out to expansion rows for easy prototyping.

Features

• Ease-of-use:
  • SmartLED Shield is fully assembled. If your Teensy has pins, then no soldering is required.
  • Teensy can easily be inserted into and removed from the shield.
  • SmartMatrix library for Arduino provides an easy development platform, along with others such as FastLED.
  • Example code is included for a quick start.
• Flexibility:
  • Drives displays with up 9k pixels (e.g. 96 x 96) with high quality settings, and even larger displays with reduced quality settings.
  • Signals on the long edges of the Teensy are brought out to expansion rows for easy prototyping.
  • The 4-pin JST-SM connector may be used to provide power to the Teensy separate from the USB connector.
  • Optionally drive DotStar/APA102-compatible LEDs using the onboard 5 volt buffers and 4-pin JST-SM connector. Mating JST-SM cable is included.
  • Panels can be daisy-chained to make large, bright, high-resolution displays.
  • Drives all 14 signals on HUB75 panels using 5 volt buffered outputs, using only 9 GPIO pins on the Teensy 4.0 or 4.1.
• Quality:
  • Provides up to a 240 Hz refresh rate.
  • Up to 48-bit color refresh is available.
  • Color (gamma) correction, and global brightness control features allow for a high level of visual quality control.

HUB75 Panels

HUB75 RGB panels are typically used for LED billboards (e.g. Times Square), making them cost-effective and readily available. They’re much cheaper per-pixel than addressable LEDs, and available in a wide range of pixel pitch (as of now, 2 mm spacing up to 10 mm spacing per LED). They do require an external controller to continually send data to the panels to refresh them line by line, and that’s where the SmartLED Shield and SmartMatrix library come in. Adafruit, Sparkfun, and other distributors carry panels that are known to be compatible with SmartLED Shield and the SmartMatrix library, but most panels on AliExpress and other sources are compatible as well.

Note: HUB75 panels have a separate power connector and require an appropriate 5 volt power supply. The SmartLED Shield does not provide power to the panel, only data signals.

The pixel pitch and "RGB" are good search terms on Aliexpress, e.g. "P6 RGB" for a 6 mm pitch RGB HUB75 panel.

Open Source

The SmartLED Shield hardware and the SmartMatrix library are released as open source. The Teensy 3 Shields and library received a lot of feedback and code contributions from the community over the years because they are open source. With the release of the more powerful Teensy 4, SmartMatrix Community member Eric Eason wrote his own code to drive LED panels with high-quality graphics from the Teensy 4, then integrated his code into SmartMatrix library. SmartLED Shield for Teensy 4 is a collaboration between myself and Eric Eason.