A Raspberry Pi Tablet, With A DSI Screen

Since the Raspberry Pi arrived back in 2012, we’ve seen no end of interesting and creative designs for portable versions of the little computer. They often have problems in interfacing with their screens, either on the very cheap models using the expansion port or on more expensive ones using an HDMI screen with associated controller and cabling. The official Raspberry Pi touchscreen has made life easier with its DSI convector, but as [jrberendt] shows us with this neat little tablet, there are other DSI-based options. This one uses a 5″ DSI touchscreen available through Amazon as well as a Pi UPS board to make a tablet that is both diminutive and self-contained.

Having fooled around ourselves in the world of Pi tablets we like this one for its clean look and a bezel that is little bigger than the screen itself. As is the case with so many Pi tablets though it has to contend with the bulk of a full-sized Model B board on its behind, making it more of a chunky brick than a svelte tablet. The screen has potential though, and we can’t help wondering whether there’s any mileage in pairing it with a much thinner Pi Zero board and a LiPo board for a slimmer alternative.

Probably the nicest Pi tablet we’ve brought you was this one, which managed to remain impressively slim despite its HDMI screen.

Putting An Out Of Work IPod Display To Good Use

[Mike Harrison] produces so much quality content that sometimes excellent material slips through the editorial cracks. This time we noticed that one such lost gem was [Mike]’s reverse engineering of the 6th generation iPod Nano display from 2013, as caught when the also prolific [Greg Davill] used one on a recent board. Despite the march of progress in mobile device displays, small screens which are easy to connect to hobbyist style devices are still typically fairly low quality. It’s easy to find fancier displays as salvage but interfacing with them electrically can be brutal, never mind the reverse engineering required to figure out what signal goes where. Suffice to say you probably won’t find a manufacturer data sheet, and it won’t conveniently speak SPI or I2C.

After a few generations of strange form factor exploration Apple has all but abandoned the stand-alone portable media player market; witness the sole surviving member of that once mighty species, the woefully outdated iPod Touch. Luckily thanks to vibrant sales, replacement parts for the little square sixth generation Nano are still inexpensive and easily available. If only there was a convenient interface this would be a great source of comparatively very high quality displays. Enter [Mike].

Outer edge of FPGA and circuit

This particular display speaks a protocol called DSI over a low voltage differential MIPI interface, which is a common combination which is still used to drive big, rich, modern displays. The specifications are somewhat available…if you’re an employee of a company who is a member of the working group that standardizes them — there are membership discounts for companies with yearly revenue below $250 million, and dues are thousands of dollars a quarter.

Fortunately for us, after some experiments [Mike] figured out enough of the command set and signaling to generate easily reproduced schematics and references for the data packets, checksums, etc. The project page has a smattering of information, but the circuit includes some unusual provisions to adjust signal levels and other goodies so try watching the videos for a great explanation of what’s going on and why. At the time [Mike] was using an FPGA to drive the display and that’s certainly only gotten cheaper and easier, but we suspect that his suggestion about using a fast micro and clever tricks would work well too.

It turns out we made incidental mention of this display when covering [Mike]’s tiny thermal imager but it hasn’t turned up much since them. As always, thanks for the accidental tip [Greg]! We’re waiting to see the final result of your experiments with this.

Finally, An Official Display For The Raspberry Pi

Yes, finally, and after years of work and countless people complaining on forums, there is a proper, official display for the Raspberry Pi.

It’s a 7-inch display, 800 x 480 pixel resolution, 24-bit color, and has 10-point multitouch. Drivers for the display are already available with a simple call of sudo apt-get update, and the display itself is available at Newark, the Pi Store (sold out) and Element14. There’s even a case available, and a stand ready to be sent off to a 3D printer.

As for why it took so long for the Raspberry Pi foundation to introduce an official display for the Pi, the answer should not be surprising for any engineer. It’s EMC, or electromagnetic compliance. The DPI (Display Parallel Interface) for the Pi, presented on the expansion header and used by the GertVGA adapter allows any Pi to drive two displays at 1920 x 1024, 60FPS. This DPI interface is an electrical nightmare that spews RF interference everywhere it goes.

raspberry-pi-touchscreen-thumbThe new display could have used the DSI (Display Serial Interface) adapter, or the small connector on the Pi that is not the camera connector. DSI displays are purpose-built for specific devices, though, and aren’t something that would or should be used in a device that will be manufactured for years to come. The best solution, and the design the Raspberry Pi foundation chose to go with, is a DPI display and an adapter that converts the Pi’s DSI output to something the display can understand.

The solution the Pi foundation eventually settled on is an adapter board that converts the DSI bus to DPI signalling. This of course requires an extra PCB, and the Foundation provided mounting holes so a Pi can connect directly to it.

While this is the first display to make use of the DSI interface, it will assuredly not be the last. The Pi Foundation has given us a way to use the DSI connector to drive cheap DPI displays. While the 800×480 resolution of the official display may be a bit small, there will undoubtedly be a few hardcore tinkerers out there that will take this adapter board and repurpose it for larger displays.

[Alex Eames] got his hands on the Pi Display a few weeks ago, you can check out his introductory video below.

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Hacklet 35 – BeagleBone Projects

The Raspberry Pi 2 is just barely a month old, and now that vintage console emulation on this new hardware has been nailed down, it’s just about time for everyone to do real work. You know, recompiling stuff to take advantage of the new CPU, figuring out how to get Android working on the Pi, and all that good stuff that makes the Pi useful.

It will come as no surprise to our regular readers that there’s another board out there that’s just as good in most cases, and in some ways better than the Pi 2. It’s the BeagleBone Black, and for this edition of the Hacklet, we’re focusing on all the cool BeagleBone projects on Hackaday.io.

lcdSo you have a credit card sized Linux computer and a small, old LCD panel. If it doesn’t have HDMI, VGA or composite input, there’s probably no way of getting this display working, right? Nope. Not when you can make an LCD cape for $10.

[Dennis] had an old digital picture frame from a while back, and decided his BeagleBone needed a display. A few bits of wire and some FPC connectors, and [Dennis] has a custom display for his ‘Bone. It’s better than waiting for that DSI display…

bed[THX1082] is making a bed for his son. This isn’t your usual race car bed, or even a very cool locomotive bed. No, this is a spaceship bed. Is your bed a space ship? No, I didn’t think so.

Most of the work with plywood, MDF, paint, and glue is done, which means the best feature of this bed – a BeagleBone Black with an LCD, buttons, a TV, and some 3D printed parts – is what [THX] is working on right now. He’s even forking a multiplayer networked starship simulator to run in the bed. Is your bed a starship simulator?

beer

Beer. [Deric] has been working on a multi-step fermentation controller using the BeagleBone Black. For good beer you need to control temperatures and time, lest you end up with some terrible swill that I’d probably still drink.

This project controls every aspect of fermentation, from encouraging yeast growth, metabolization of sugars, and flocculation. The plan is to use two circuits – one for heating and one for cooling – and a pair of temperature sensors to ensure the beer is fermenting correctly.


If you’re looking for more BeagleBone Projects, there’s an entire list of them over on Hackaday.io with GLaDOs Glasses, Flight Computers, and Computer Vision.

Using Cell Phone Screens With Any HDMI Interface

Thanks to the worldwide proliferation of smartphones, tiny high-resolution displays are common and cheap. Interfacing these displays with anything besides a phone has been a problem. [twl] has a board that does just that, converting HDMI to something these displays can understand, and providing a framebuffer so these displays can be written to through small microcontrollers.

[twl] is using a rather large FPGA to handle all the conversion from HDMI to the DSI the display understands. He’s using an Xilinx Spartan-6-SLX9, one of the most hobbyist friendly devices that is able to be hand soldered. Also on the board is a little bit of SDRAM for a framebuffer, HDMI input, and a power supply for the LCD and its backlight.

On the things [twl] has in his ‘to-do’ list, porting Doom to run on a cellphone display is obviously right at the top. He also wants to test the drawing commands for the Arduino side of his board, allowing any board with the suffix ~’ino to paint graphics and text on small, cheap, high-resolution displays. That’s a capability that just doesn’t exist with products twice [twl]’s projected BOM, and we can’t wait to see what he comes up with.

You can check out the demo video of [twl]’s board displaying the output of a Raspberry Pi below. If you look very closely, you’ll notice the boot/default screen for the display adapter is the Hackaday Jolly Wrencher.

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Hard Core Nintendo DSI Hacking

dsi (Custom)

So, you hacked your DSI did you? Let me guess, you ran a flash cart. No? You probably added some LEDs then right? No? You must be pretty hard core, did you add a NES controler? No? Well what did you do?

We still have no idea what this guy is doing. But he is doing it very meticulously. We found [Micah Dowty]’s photo stream on flicker and we were instantly pulled in. He has done some extensive modifications to his DSI. He has spread its innards for all to see and begun hacking. It appears as though most of this is for memory dumps and direct access to the RAM in the unit, but frankly we just want to stare at these pictures.

Nintendo DSi Teardown

dsiteardown

Now that the Nintendo DSi has been officially released in the US, the team at iFixit has worked their magic. That magic being: completely disassembling it. They found the new 840mAh battery to be much smaller than the DS Lite’s 1000mAh. The device features two cameras, but both are a paltry 0.3megapixels. They note that this is the first Nintendo device that they’ve taken apart that didn’t require a tri-wing screwdriver.

Many more DSi compatible flash carts are available now than our initial report in December, so you can pick up a Nintendo DSi for homebrew without worry.

[via iFixit blog]