This project interfaces with a D8M camera module, processes the image, and streams it to a flip-dot display.
A "flip-dot" display is made up of mechanical disks that flip back-and-forth to show white or black. They were popular as signs on buses, and at train stations. Each mechanical pixels reacts surprisingly fast. See the Demo_video2 link below to see it in operation.
If the link below does not work, download the demo video file from: https://github.com/delhatch/Flipdot_video/blob/master/flipdot_display_demo.mp4
The incoming camera video (at 60 fps) is de-Bayered, a threshold is applied (black/white pixel), low-pass filtered, down-sampled, and then sent at 19,200 baud to a flip-dot display.
This project uses the Cyclone IV FPGA used in the DE2-115 evaluation board to:
a) configure and interface to the camera module, and
b) buffer the raw video into an SDRAM frame buffer. The FPGA has two VGA frame buffers and the FPGA creates the VGA waveforms for the monitor. A physical switch selects between one frame buffer that holds the RGB (normal) video, and a second VGA frame buffer that holds a full frame of the black/white pixel data. The .mp4 video included in this project shows me switching between the two.
c) Simulataneously with that, I down-samples the resolution (to the value defined in "flipdot_params.h"), and low-pass filter the video frames, and then store that data to a 56 x 24 bit flipdot frame buffer.
d) The final step is to have a (custom) UART read the flip-dot frame buffer and transmit the image to the flip-dot display at 19200 baud.
*** Possible Improvements ***
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Auto-exposure control on the source video (to account for changing light conditions).
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Temporally filter the pixels, or apply hysteresis, so that the flip-dot display does not flip pixels back-and-forth when there is no image motion (for pixels at the threshold of black/white).