Experimenting with 8-bit graphics

[Vinod] has done a lot of work with microcontrollers, but this is his first try at displaying graphics using composite video. He had a small PAL television on hand, and an ATmega32 which just needs a stable clock source and a few resistors to get things going.

There are a lot of other hacks around that use composite video out with microcontrollers. But this is a ground-up approach which will help you understand the concepts behind these graphics. [Vinod] started by calculating the possible resolution. He needs to hold a frame buffer in memory, and since his chip has just 2 kilobytes of SRAM this will be the limiting factor. He settled on a display area of 128 by 64 pixels. This divides evenly by 8 so he’s not wasting any bits, and it totals 1k, leaving half of the SRAM for use in calculating the shapes which populate the buffer. An interrupt service routine runs ever 64 microseconds to feed data for each line of the display.

With the scanning in place, he moved on to fill the frame buffer. Two functions are used, one which sets a pixel the other clears a pixel. He compares these to using a pencil and an eraser. By calling these functions from his main program he is able to draw lines, boxes, and circles. A bit of creative looping and he’ll have animations as well, but that’s a concept for a different post.

Interactive digital fireplace is great for those chilly winter evenings


We’ve all seen them – those fireplace DVDs that seem to pop up on grocery store endcaps and get traded in white elephant gift exchanges. If you don’t happen to have a fireplace in your home they might make a reasonable solution, but [Nick] from the Gadget Gangster thought it would be far better if you could create your own interactive digital fireplace instead.

Using the Gadget Gangster Propeller USB platform and ProtoPlus board, his fireplace merges various video segments together based on user input, and plays them on any TV that comes equipped with RCA jacks. The process is fairly straightforward, and involves wiring up switches along with audio and video output to the Propeller board via the ProtoPlus board. The remainder of the work is done using software, requiring the user to select and encode video segments for storage on an SD card. [Nick] does however provide a whole set of clips for download, should you want to take the quicker route.

After encoding and categorizing the video clips to coincide with the “stoke” and “add wood” user input buttons, the Propeller does the rest of the work, randomly selecting clips from the appropriate category when requested.

The result is admittedly a bit Lo-Fi, though we thinks it’s cool and prefer to call it “retro” instead. It might not be a Hi-Def fireplace recording, but it’s far nicer to snuggle up to a hand made fireplace rather than a DVD you picked up as an afterthought.

Continue reading to see a quick demo video of the digital fireplace in action.

Continue reading “Interactive digital fireplace is great for those chilly winter evenings”

Composite video through cat5


[mixadj] needed to run some video cable from one part of his house to another. He was lacking the proper amount of video cable, but had a bunch of cat5 laying around. so he built a converter to run his composite signal through the cat5. He states that he wouldn’t run it more than 70 feet without amplifying the audio somehow. Aside from that, the performance is supposedly decent.  This just adds to the multitude of other uses for that Ethernet cable. We’ve seen voice, data, composite video, VGA, and power. What else have you seen run over cat5?