Micro-SD Card Slot Abused As VGA-Port

dvdkhlng writes "The Ben NanoNote open-source hand-held computer has often been criticized for not being very extensible hardware-wise. A community effort now starts to challenge this by shipping the so-called UBB board, which plugs into the micro-SD port, making 6 I/O lines available to hardware hackers. The most impressive use so far is this VGA port implemented by just a few resistors, with signal-generation mostly controlled by software. The guy who did this calls it an 'unexpected capability.' Schematics and source code are available under the GPL."

Comments

Great-grandson of "Cheap Video Cookbook"

[shoppa]

Don Lancaster did a pretty good job explaining raster-scan-generated-by-cleverness-of-using-main-CPU in the Cheap Video Cookbook. Back in 1978.

So slashdot is about, oh, 33 years late :-).

Re:Great-grandson of "Cheap Video Cookbook"

[Anonymous Coward]

The concept is as old as time. There are also lots of similar VGA out implementations for various microcontrollers, FPGAs, etc. What's new here is that the MMC controller is used to send out the pixels, which a) allows for a comparably high resolution, b) makes the operation reasonably efficient (i.e., in the future, it may even be possible to do other things in parallel), and c) hides some of the complexities of instruction timing in modern CPUs, with caches, DRAM, multiple bus masters, etc. Within the qi-hardware community, it was also a nice surprise to discover that our little Ben could actually do this.

Re:Great-grandson of "Cheap Video Cookbook"

[DarkOx]

Well the technique was pretty darn common in the 8 bit home computer era. So you are right in that this is not novel, but it shows its still a good method to add video to hardware that the manufacturer maybe never intended to have video out. I think this is a pretty good "News For Nerds" post even if its strictly New(s) that you can do this. I think it might be an interesting technique to apply in things like Rockbox and plug computers, as well.

Re:Great-grandson of "Cheap Video Cookbook"

[dvdkhlng]

BTW, this mailing-list post contains all the details about how the MMC (SDIO) controller is used here. An earlier version relied on doing bit-banging with the MMC lines programmed as general-purpose I/Os, but didn't even reach QVGA resolution this way.

Nice, but...

[luvirini]

While the GPL part is nice, and hack can be fun, the question still arises why start with such a limited platform in the first place if you have the need for more?

Re:Nice, but...

[pvera]

Because it opens the possibilities of other "unexpected" hacks that people can't visualize simply by looking at the available ports for a given device (not just the one in the article). If you can plug that thing into the microSD port and make it talk to VGA with 10 resistors and a bit of software, it means you can probably use microSD as a connector on other devices knowing that the connector and board are not only dirt cheap but open.

Re:Nice, but...

[cfriedt]

It's often ___immeasureably__ useful to get some (any) kind of console output when porting Linux to an existing device running e.g. windows mobile 5 or 6. Take a look at HaRET. Porting is often harder than most would imagine, as some manufacturers actively use hardware obfuscation methods to prevent hacktivists from getting console access.

Try to imagine how long it would take to use LEDs or haptic feedback to iteratively check all conditions required to bring up Linux on a board without a serial port. The first thing you would probably do is try to use a hardware subsystem that was known to work and fashion a serial port out of it. This is the same concept but graphical.

Great work!

Re:Why?

[cptdondo]

For one it's fun. It's OK to have fun. If we only do those things that need to have a (serious) reason, we'd never have any fun. You must have gone straight from diapers to curmudgeon, without the usual goofy and fun states.

For another, this would be great for a low-cost embedded project. I can easily see this being adapted to an embedded playroom I play with.

Lastly, ti's cool.

Don Lancaster

[Anonymous Coward]

"Cheap Video Cookbook" is exactly what came to mind when heard about the VGA port (I have a Ben Nanonote and subscribe to the mailing list). I enjoyed Don Lancaster's books so much when I was a kid. He taught me not to be afraid of a soldering iron. He showed me how to disassemble software. But mostly, he explained hacker values better than anyone.

In one of his columns, he told the flute story, and it always stayed with me. I became a teacher in College ten years ago, and I always repeat this story to my students. Here it is.

"Many years ago, I was at a rock concert. The opening act was a single flute player standing solo in front of the closed stage curtains. His job was to warm up the audience for the high priced talent that was to follow. He was good. But as he went along, the musical vibes got stranger and stranger, then totally bizarre. He was playing chords on his flute. Combined with utterly unbelievable riffs. Much of the audience got impatient and bored at what seemed like a bunch of god-awful squawks. Then I happened to notice a friend beside me who had both been in and taught concert band. He was literally on the edge of his seat. He turned to me and slowly said 'You Can't Do That With a Flute.'

Of the thousands and thousands of people in the theater audience, at most only five realized they were witnessing a once-in-a-lifetime performance of the absolute mastery of a difficult and demanding instrument.

Always play for those five."

Re:Don Lancaster

[Anonymous Coward]

Did you read the story in the paper about Joshua Bell, one of the world's top violinists who dressed up as a bum and played the violin for day in the subway system? There was a similar moral to the story: some people took notice and went on their way, most didn't and a very few (I think the # was also 5) stopped and stayed to listen. Only one of those who stayed recognized who the musician really was.

link to story: http://www.freakonomics.com/2007/04/09/what-happens-when-a-maestro-plays-the-subway/

Re:Why?

[LongearedBat]

why the f^@k would anyone even care

Some of us nerds care 'cos we like playing with tech. And who knows what other interesting things this might lead to, some of which might turn out to be very useful?

Re:Why?

[Jafafa Hots]

Why comment on slashdot articles? What's that going to achieve?

Abused?

[PPH]

Why abused? Re-purposed sounds more accurate.

I've used a lot of 'ports' for functions not originally envisioned in their design (Rule 34 applications included) and its only abuse if you don't get permission first.