Convert A Curbside CRT TV Into An Arcade Monitor

May 30, 2018 by Tom Nardi 29 Comments

While an old CRT TV may work well enough on a MAME cabinet project, the real arcade purists are quick to point out that a proper arcade monitor and a TV aren’t the same thing. A real arcade board uses RGB to connect to the monitor, that is, direct control over the red, green, and blue signals. Conversely video over coax or composite, what most people associate with old CRT TVs, combine all the video information down into an analog signal. Put simply, RGB allows for a much cleaner image than composite.

Many in the arcade restoration scene say that trying to convert a bog standard CRT TV into a RGB monitor isn’t possible, but [Arcade Jason] had his doubts. Over on his YouTube channel, he’s recently posted a tutorial on how to go from a trashed CRT TV to a monitor worthy of proper arcade gaming with relatively little work. As real arcade monitors are becoming increasingly rare, these kind of modifications are likely to get more common as coin-op gamers look to keep the old ways alive.

Now obviously every TV is going to do be different inside. All CRT TVs contain high voltages, and on some the circuit boards aren’t even mains-isolated, so take care if you try this. [Jason] certainly doesn’t claim that the method he demonstrates will work on whatever old TV you happen to have kicking around. But the general idea and some of the techniques he shows off are applicable to most modern TVs, and can help you tailor the method to your particular piece of gear. It all starts with a wet finger. Seriously.

[Jason] demonstrates a rather unique way of determining which pins on the TV’s control chip are responsible for the individual color signals by wetting his finger and sliding it over the pins. When a change in color is seen on the displayed image, you know you’re getting close. We can’t say it’s the most scientific or even the safest method, but it worked for him.

He then follows up with a jumper wire and resistor to find the precise pins which are responsible for each color, and solders up his actual RGB connection for the arcade board. In addition to the three color wires, a sync signal is also needed. This is the same sync signal used in composite video, so all that’s needed is to solder to the pad for the original composite video jack. Add a ground signal, and you’ve got yourself a proper RGB monitor.

Interestingly, this one has come full circle, as [Jason] says his attempt was inspired by an old post on Hackaday. It’s the Circle of Hacker Life.

[Thanks to Seebach for the tip]

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Pocket-Sized Workstation Sports Pi Zero, Pop-Up Screen

April 11, 2018 by Dan Maloney 17 Comments

Many of us could use a general-purpose portable workstation, something small enough to pocket but still be ready for a quick troubleshooting session. Terminal apps on a smartphone will usually do the job fine, but they lack the panache of this pocketable pop-top Raspberry Pi workstation.

It doesn’t appear that [Michael Horne] has a specific mission in mind for his tiny Linux machine, but that’s OK — we respect art for art’s sake. The star of the show is the case itself, a unit intended for dashboard use with a mobile DVD player or backup camera. The screen is a 4.3″ TFT with a relatively low-resolution, so [Michael] wasn’t expecting too much from it. And he faced some challenges, like dealing with the different voltage needs for the display and the Raspberry Pi Zero W he intended to stuff into the base. Luckily, the display regulates the 12-volt supply internally to 3.3-volts, so he just tapped into the 3.3-volt pin on the Pi and powered everything from a USB charger. The display also has some smarts built in, blanking until composite video is applied, which caused a bit of confusion at first. A few case mods to bring connectors out, a wireless keyboard, and he had a nice little machine for whatever.

No interest in a GUI machine? Need a text-only serial terminal? We’ve seen that before too. And here’s one with a nice slide-out keyboard built in.

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Eavesdropping On A VGA Monitor’s Conversations

March 29, 2018 by Dan Maloney 28 Comments

Did you ever wonder what your monitor and your computer are talking about behind your back? As it turns out, there’s quite a conversation going on while the monitor and the computer decide how to get along, and sniffing out VGA communications can reveal some pretty fascinating stuff about the I²C protocol.

To reverse engineer the configuration information exchanged between a VGA monitor and a video card, [Ken Shirriff] began by lopping a VGA cable in two. The inside of such cables is surprisingly complex, with separate shielding wires for each color and sync channel and a host of control wires, all bundled in multiple layers of shielding foil and braid to reduce EMI. [Ken] identified the clock and data lines used for the I²C interface and broke those out into a PocketBeagle for analysis using the tiny Linux machine’s I²C tools.

With a Python script to help decode the monitor’s Extended Display Identification Data (EDID) data, [Ken] was able to see everything the monitor knows about itself — manufacturer, serial number, all the supported resolution modes, and even deprecated timing and signal information left over from the days when CRTs ruled the desktop. Particularly interesting are the surprisingly limited capabilities of a VGA display in terms of color reproduction, as well as [Ken]’s detailed discussion on the I²C bus in general and how it works.

We always enjoy these looks under the hood that [Ken] is so good at, and we look forward to his reverse engineering write-ups. His recent efforts include a look at core memory from a 50-year old mainframe and reverse engineering at the silicon level.

Shoot-And-Forget Digital Photo Frame

March 5, 2018 by James Hobson 28 Comments

Digital photo frames these days require you to manage the photos stored on it or the cloud-based service tied to the frame’s manufacturer. [Henric Andersson] realized that he and his wife take a lot of photos but find little time to go through them — like photo albums of days past — and add them to any photo frame-like appliance or service. Since Google photos can do a lot of the sorting for them, he decided to incorporate that into a digital photo frame.

Using his wife’s old Viewsonic 24” 1080p monitor, he cracked it open and incorporated the screen into a 24×16 distressed wood frame — reinforcing it to account for the bulky, built-in power supply with pieces of HDF and a lot of glue. The brains behind this digital photo frame is a Raspberry Pi 3 he received from a friend. To turn the whole on/off, he built a small circuit but it turned out it wasn’t strictly necessary since everything started just fine without it.

While functionally complete, it needed one more addition. A little thing called ‘color temperature calibration’ — aka white balance.

Finding the TCS34725 RGB color sensor by Adafruit — and readily available code for easy integration — [Andersson] puzzled over how to add it to the frame. To disguise it while retaining its effectiveness, he had to glue it to the rear of the frame after drilling a hole in the top piece and sticking a plastic stick through the hole to let light through to the sensor.

To get the photos to display, [Henric Andersson] says all he did was add a few queries to Google Photos and it will display all your relevant photos that have been synced to the service. For a breakdown of that side of this hack, check out his other post with the details.

While Google Photos deftly displays photos of various orientations, sizes, and aspect ratios, we’ve featured a digital photo frame that handles the task a little differently.

Software Defined Television On An ESP32

February 22, 2018 by Dan Maloney 24 Comments

Composite video from a single-board computer? Big deal — every generation of Raspberry Pi has had some way of getting composite signals out and onto the retro monitor of your choice. But composite video from an ESP32? That’s a thing now too.

There are some limitations, of course, not least of which is finding a monitor that can accept a composite input, but since [bitluni]’s hack uses zero additional components, we can overlook those. It really is as simple as hooking the monitor up to pin 25 and ground because, like his recent ESP32 AM radio station, the magic is entirely in software. For video, [bitluni] again uses his I²S tweaks to push a lot of data into the DAC really fast, reproducing the sync and image signals in the 0-1 volt range of the PAL composite standard. His code also supports the NTSC standard, but alas because of frequency limitations in the hardware it’s monochrome only for both standards, at least for now. He’s also got a neat trick to improve performance by running the video signal generation and the 3D-rendering on separate cores in the ESP32. Check out the results in the video below.

It looks like the ESP32 is getting to be one of those “Is there anything it can’t do?” systems. Aside from radio and video, we’ve seen audio playback, vector graphics, and even a Basic interpreter easter egg.

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Bark Back IoT Pet Monitor

January 5, 2018 by James Hobson 6 Comments

Does your pet get distressed when you’re not home? Or, perhaps their good behaviour slips when you’re not around and they cause a ruckus for the neighbours. Well, [jenfoxbot] has just such a dog, so she built a ‘bark back’ IoT pet monitor to keep an eye on him while she’s out.

The brains and backbone of the pet monitor is the ever-popular Raspberry Pi 3. A Sparkfun MEMS microphone breakout board listens for any unruly behaviour, with an MCP3002 analog to digital converter chip reading the mic input. Some trial-and-error coding allowed her to set a noise threshold that — once exceeded — will trigger an audio file, shushing her dog. It also logs events and uploads any status updates to a CloudMQTT server to be monitored while away from home. Her Imgur build album can be found here, and the GitHub project page is here if you want to build your own!

Check out the demo video after the break, that was probably confusing for her good dog, Marley.

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A TEMPEST In A Dongle

November 26, 2017 by Dan Maloney 27 Comments

If a couple of generations of spy movies have taught us anything, it’s that secret agents get the best toys. And although it may not be as cool as a radar-equipped Aston Martin or a wire-flying rig for impossible vault heists, this DIY TEMPEST system lets you snoop on computers using secondary RF emissions.

If the term TEMPEST sounds familiar, it’s because we’ve covered it before. [Elliot Williams] gave an introduction to the many modalities that fall under the TEMPEST umbrella, the US National Security Agency’s catch-all codename for bridging air gaps by monitoring the unintended RF, light, or even audio emissions of computers. And more recently, [Brian Benchoff] discussed a TEMPEST hack that avoided the need for thousands of dollars of RF gear, reducing the rig down to an SDR dongle and a simple antenna. There’s even an app for that now: TempestSDR, a multiplatform Java app that lets you screen scrape a monitor based on its RF signature. Trouble is, getting the app running on Windows machines has been a challenge, but RTL-SDR.com reader [flatfishfly] solved some of the major problems and kindly shared the magic. The video below shows TempestSDR results; it’s clear that high-contrast images at easiest to snoop on, but it shows that a $20 dongle and some open-source software can bridge an air gap. Makes you wonder what’s possible with deeper pockets.

RF sniffing is only one of many ways to exfiltrate data from an air-gapped system. From power cords to security cameras, there seems to be no end to the ways to breach systems.

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