Color NTSC video directly from an AVR chip

color-ntsc-from-avr-chip

We’ve seen composite video out from AVR chips many times before. But we can’t remember coming across one that managed to produce a color signal. This project does just that, producing a color video signal from an ATmega168 without using external integrated circuits.

[CNLohr] is seen here showing off his accomplishment. You’ll remember him from the glass-slide PCB server project he’s been working on recently. This time around it’s a small piece of gaming hardware which he’s working on. But using four pins from the microcontroller, connected via resistors in parallel, he is able to generate a color NTSC signal without using a chip like the AD723.

After the break you can see the two minute demo in which he shows the game running for just an moment, then gives a general overview of how the signals are being built. There isn’t a ton of explanation, but he did post his code as well as a resource for you to teach yourself more about the NTSC standard. Maybe you can make a color version of that AVR tetris game?

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Hacking a PAL SNES to output 50Hz or 60Hz with a single switch

snes-pal-ntsc-mod

[Derecho] grabbed a PAL format Super Nintendo but wanted to make it play nicely with a 60 Hertz NTSC screen. His hack added a single switch to choose between 50 Hz and 60 Hz.

Take a look at the image above to see his alterations to the mainboard. The jumpers soldered to the two chips at the top are by far the trickiest part of the project. Each of the pins he soldered to needed to first be lifted from the PCB pad so that they no longer make contact with the etched traces. The technique he used involves heating the pin with an iron, then gently lifting it with a pin or a razor knife/blade. If you’ve got some experience populating SMD boards with a handheld iron this shouldn’t prove too difficult. The rest of the hack involves adding a 3-position switch (along with a 2k2 resistor) to choose between output modes based on what format game is being played.

Using an oscilloscope as a composite video adapter

Confronted with a monitor that would display neither HDMI signal, nor composite video, [Joonas Pihlajamaa] took on a rather unorthodox task of getting his oscilloscope to work as a composite video adapter. He’s using a PicoScope 2204 but any hardware that connects to a computer and has a C API should work. The trick is in how his code uses the API to interpret the signal.

The first thing to do is make sure the voltage levels used in the composite signal are within the tolerances of your scope. [Joonas] used his multimeter to measure the center pole of the RCA connector and found that the Raspberry Pi board puts out from 200 mV to 2V, well within the PicoScope’s specs. Next he started to analyze the signal. The horizontal sync is easy to find, and he ignored the color information — opting for a monochrome output to ease the coding process. The next big piece of the puzzle is to ascertain the vertical sync so that he knows where each frame starts. He got it working and made one last improvement to handle interlacing.

The proof of concept video after the break shows off the he did. It’s a bit fuzzy but that’s how composite video looks normally.

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Controlling a TV with a microcontroller

Here’s two builds that print text to a TV with only two pins:

Still Alive with an Arduino

After seeing all the builds that play Still Alive, [Bob] decided to take a 1972 amber monitor and recreate the cut scene at the end of PortalThe build uses the TVout library for Arduino. There were a few problems with running the Unix and Still Alive animations at the same time, so [Bob] flips a bit in the EEPROM at the end of the command line animation and restarts into GLaDOS’ report. You can check out the old school color monitor here

ATMega Video Text Generator

[Stian] didn’t think his build was good enough for Hackaday, but his friend [Mikael] thought otherwise. [Stian] wrote a library to generate an NTSC video signal in real time. It’s a text-based build with 37×17 character resolution and only requires about 3kB of RAM. As a bonus, it only takes up two pins on [Stian]’s ATMega128.

You can check out the videos for both these builds after the break.

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Thinner client using STM32 and NTSC monitor

[David Cranor], along with [Max Lobovsky’s] help, managed to build a thin client that uses an NTSC television as a monitor for only $6. This is his first foray into the world of ARM architecture and he has vowed to never use an AVR again. The powerful little chip uses timers to manage sync and DMA to transfer the full 480×240 frame buffer to the screen. Overclocked at 80 MHz there’s a lot of potential in this little board and he plans to take on the challenge of a full-color display for his next trick.

Coyote-1 guitar pedal available now


OpenStomp’s Coyote-1 is now available for $349. The guitar effects pedal lets users design and upload their own effects to the device. It has two stomp switches with LEDs, an LCD display, and four user assignable knobs. The back has 1/4″ in/out and one selectable 1/4″. It also features NTSC composite out, a headphone jack, mini-USB for uploading, and an RJ11 I2C bus for expansion. The processor is a Parallax Propeller Chip. While the OS on the pedal is open source, the hardware design and effect design software are not. You can check out the source and product manual on their forum. If you’re more interested in breadboarding hardware, you might like the Beavis Board we covered earlier.

[via Create Digital Music]