Displaying video and gifs on RGB LED matrices


[Mathieu] was on holiday in China and picked up some fun toys while perusing the numerous electronics markets there. The most interesting things he discovered were a pair of RGB LED matrices. They came in two different flavors, one made for indoor and one for outdoor displays, sporting a 64×32 and 32×16 resolution, respectively.

If you’ve read his blog before you know he is a big fan of LED matrices, so it’s only natural that bought a whole bunch of them and started experimenting once he got home. Using the same Atmel FPSLIC LED matrix control board he showed off in this previous hack, he was able to get the LED matrices up and running in no time. He adapted his webcam project to utilize the new panels, and he added a whole new feature as well. Via MatLab, he can now display any sort of animated gif on the panels, as you can see in the video below. The panels look great, and if we had a few of these around, there’s no doubt we would probably play this video on infinite repeat.

He says that the despite their somewhat questionable origins, the panels are of top notch quality, and he is willing to organize some sort of group buy if others are interested.

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Webcam images processed and played back on LED display

[Mathieu] has bee working to refine the code running on an LED matrix, and added some neat display tricks along the way. He wanted to make the display directly addressable from a computer. The 96×64 bi-color LED display is powered by an Atmel FPSLIC and already used double-buffering. Enabling a PC to write directly to one of the buffers was not too hard, requiring just a bit of optimization to get the timing right. From the look of the video after the break, he nailed it.

The video feed is generated from a webcam stream using Matlab to process each image. Just 50 lines of code captures a frame, sizes it appropriately, converts the result to black and white for edge detection, then finishes the job by compressing image data for transmission to the embedded processor. We’d like to say it’s easier that it sounds but we’re pretty impressed with this work. The display manages about 42 Hz with the current setup.

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FPSLIC powered LED matrix

[Mathieu] built this display in hopes that he can play pong on it. You can imagine the headache that awaits when trying to figure out how to drive the 6144 bi-color LEDs. I must have worked out because the thing looks great in the video after the break. The solution he chose was a bit unfamiliar to us though. He used a Field Programmable System Level Integrated Circuit produced by Atmel, or FPSLIC. This is a kind of mash-up of components we’re more accustomed to.

The AT94K is a single chip that houses an 8-bit AVR microcontroller, and FPGA, and SRAM. This project uses that FPGA to handle the multiplexing of the display via code written in VHDL. The AVR core receives data via a USB port, stores two images in the SRAM (one for each LED color), and then outputs it to be drawn on the display. On second thought, this project sounds like fun and it’s a great way to get start learning that VHDL you’ve been putting off. [Read more...]