Want to add a lot of LEDs to your Arduino project? HUB75 RGB panels are a great way to do this as they are much cheaper than addressable Neopixel/WS2812 LEDs (typically 10% the cost per LED). They are also available in a range of pixel densities (from 2 mm to 10 mm pitch) to better fit the needs of your project. However, it’s complicated to use a microcontroller to display high-quality graphics on a HUB75 panel, as the panels require precise timing and constant refreshing with pixel data. That’s where the SmartLED Shield for Teensy 4 comes in.

High-quality, Easy-to-implement LED Graphics

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.

Installation Video

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.

Example Code

It’s easy to get started with the included examples, which give a good idea of the SmartMatrix library and SmartLED Shield’s capabilities.

LED Art

Use the FastLED library to draw beautiful patterns to the SmartMatrix library’s pixel buffers, and they get refreshed on the panel in the background. Take advantage of the SmartMatrix library’s color correction and brightness control features which are applied automatically while maintaining color depth, so your patterns look great. See the FastLED_Functions example.

Animated GIFs

Both retro pixelated graphics and full motion video look good displayed on a LED matrix. Use the Teensy 4.1’s built-in micro SD Card slot to store GIF files for playback using the AnimatedGIFs example.

Basic Graphics

Draw basic shapes, text, bitmaps, etc. to the display, with the FeatureDemo and Bitmaps examples.

Display Information

You can display scrolling or static text on layers in front of the background, making adding information in front of nice looking graphics easy to code. See the FeatureDemo and MatrixClock examples.

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.

HUB75 Panels Ranging from P2 to P10 pitch

Teensy

Teensys are small, well-featured, low-cost microcontroller boards designed by PJRC. Best of all, the boards have excellent development support and a large community. They’re the perfect solution to build an LED board around.

Teensy 4.0 vs 4.1

SmartLED Shield works with two variants of Teensy 4, the 4.0 and 4.1, with the 4.1 being the higher-powered option. Teensy units are available for purchase along with shields during the campaign. Please note that SmartLED Shield kits come with headers required to mate your Teensy to the board, but if you buy a Teensy through the campaign, you will need to solder the Teensy headers yourself. Units with pre-soldered headers can be found on Sparkfun.

As stated on the PJRC website, these are the main differences between the two units:

Teensy Pin Usage

There are still plenty of pins on the Teensy 4 left over for other uses after driving a HUB75 panel. The shield provides jumper configurations that provide even more flexibility. To use hardware SPI, we recommend Teensy 4.1 which has a convenient alternate SPI port. The pins for APA102 driving are free for other uses if not driving APA102 LEDs - they aren’t needed for HUB75 driving.

Support & Documentation

• SmartMatrix library 4 GitHub (find hardware in extras/hardware)
• SmartLED Shield for Teensy 4 Documentation
• SmartMatrix Community is a great place to see what people are doing with the SmartLED Shield and SmartMatrix library, ask questions, get help with your project, or share content like animated GIFs.
• Feel free to post any questions you have in the SmartMatrix Community, ask a question through the campaign page, or email hello@pixelmatix.com.

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 Pixelmatix and Eric Eason.