32x32 RGB Display Daisy-Chain

[dleonardjr]

Hello, I currently have one Medium 32x32 RGB LED display and I am interested in connecting up another and daisy-chaining the output. To drive the first display I am using an Arduino Mega with the RGBmatrixPanel and Adafruit_GFX libraries. Are you aware of any Adafruit or external resources which may describe this process or even give example code? Thank you.

[pburgess]

The RGBmatrixPanel library doesn't handle daisy-chaining. This is on purpose and by design...the Arduino just isn't fast enough for doing this at acceptable refresh rates, and the most popular models lack sufficient RAM for extra matrices.

If you crawl around inside the library, you can see an innermost loop where it's pushing 32 pixels (one row) of data to the matrix. The principle behind daisy-chaining is to push an additional 32 pixels worth (second screen first). This totally changes the PWM timing and cuts the refresh rate in half.

Doing this at a respectable rate requires a more substantive microcontroller. I've seen projects using the BeagleBone Black, Parallax Propeller and other high-performance chips...but they tend to all use the 32x16 display...so there'd still be some work to be done to get these working with the 32x32. You can google around and see what others have done.