As the adage goes, “if you want something done right, do it yourself.” Desirous of a tablet but preferring to eschew consumer models, [Stefan Vorkoetter] constructed his own compact and lightweight Raspberry Pi tablet, covering several extra miles in the process.
The tablet makes use of a Raspberry Pi 3 and the official touchscreen, with the final product marginally larger than the screen itself. Designed with a ‘slimmer the better’ profile in mind, [Vorkoetter] had to modify several components to fit this precept; most obvious of these are the removal of the Pi’s GPIO headers, USB, and Ethernet ports, and removing the USB power out port from the touchscreen controller board so the two could be mounted side-by-side.
An Adafruit PowerBoost 1000C handles charging the 6200 mAh battery — meaning up to six hours(!) of YouTube videos — via a micro USB, but only after [Vorkoetter] attached a pair of home-made heatsinks due to negligible air flow within the case. A modified USB audio adapter boosts the Pi’s audio capabilities, enabling the use of headphones, a mic, and a built-in speaker which is attached to the tablet’s back cover.
Continue reading “Huge Functionality, Small Package: A Custom Tablet, Raspberry Style”
The Subaru BRZ (also produced for Toyota as the GT86) is a snappy sportster but [megahercas6]’s old US version had many navigation and entertainment system features which weren’t useful or wouldn’t work in his native Lithuania. He could have swapped out the built in screen for a large 4G Android tablet/phone, but there’s limited adventure in that. Instead, he went ahead and built his own homemade Navigation system by designing and integrating a whole bunch of hardware modules resulting in one “hack” of an upgrade.
The system is built around a Lenovo 4G phone-tablet running android and supporting GPS, GLONASS as well as the Chinese BeiDou satellite navigation systems. He removed the original daughter board handling the USB OTG connection on the tablet, and replaced it with his version so he could connect it to his external USB board via a flat ribbon cable. The USB board contains a Cypress 4-port USB hub. One port is used as the USB HID device to allow external buttons for system control — Power, Volume Up/Down, Fwd/Rev, Play/Pause, and Phone Answer/Hangup. The second port is used as a regular USB input to allow connecting external devices such as flash drives. The third one goes to a reversing camera while the fourth port goes to a USB DAC.
The USB DAC is another hardware board by itself and also includes a Bluetooth module which integrates his phone’s audio and control functions with the on-board system. There’s also an audio mixer which allows him to use the phone audio without having to miss out on the navigation prompts from the tablet. Both boards also contain several peripheral circuits such as amplifiers and DC power supplies. Audio to the speakers is routed through six LM3886 based power amplifier boards. And the GPS module receives its own special low-noise amplifier board to ensure extremely strong reception at all times. That’s a total of ten boards custom built for this project. He’s also managed to source all the original harness connectors so his system is literally a snap in replacement. The final assembly looks pretty dashing.
For some strange reason, the Lenovo tablet uses 4.35V as the ‘fully charged” value for its LiPo instead of the more common 4.20V, so even with the whole system connected to a hefty 12V lead acid battery from which he’s deriving the 4.20V charging voltage for the tablet, it still complains about “low battery” — and he’s looking for advice on how he can resolve that issue short of blowing up the LiPo by using the higher charge voltage. Besides that, he’s (obviously a kickass) hardware designer and a little bit rusty on the software and programming side of things, for which he’s looking for inputs from the community. His introductory video is almost 30 minutes long, but the shorter demo video after the break shows the system after installation in his car. He’s posted all of his Altium hardware source files on the project page, but until he shares PDF versions, it would be difficult for most of us to look at his work.
Continue reading “Homemade Subaru Head Unit is Hidden Masterpiece”
[ttsiodras] tells an epic tale of getting a custom Debian kernel installed on an Asus MemoPAD (ME103K) tablet. Skipping to the end of the saga, he discovers what looks like serial data coming out on the headphone jack when the system boots, but the signal was so distorted that he couldn’t simply interpret it. The solution turns out to be attaching a level-converter chip.
A level converter is a non-inverting amplifier, usually with a Schmitt trigger for immunity against noise. In this case, it acts like a “binarizer” — outputting a high voltage when the input rises above a threshold, and a low when it drops below. It’s the right part when you need to clean up a messy digital signal, and in this case works just fine because the capacitive distortion effects slow down both the leading and trailing edges of the signal, keeping the serial data’s timing intact.
That was the spoiler. If you want to read up on putting a custom Linux on an Android device, check out [ttsiodras]’s first post where he backs the machine up, and the second where he gets his custom kernel up and running. If you’re ever faced with an Android tablet that hasn’t been owned yet, or if you just have a DIY streak, this should help you get started.
Using the audio jack for serial is actually not uncommon, and discovering a serial terminal that listens at boot time is our favorite way to wedge a Linux OS into odd devices. So when you see a funny, distorted signal coming out at 115,200 baud, take a moment to clean its edges up and see what you’ve got.
Computer handwriting recognition is very cool by itself, and it’s something that we’d like to incorporate into a project. So we went digging for hacker solutions, and along the way came up with an interesting bit of history and some great algorithms. We feel like we’ve got a good start on that front, but we’re stuck on the hardware tablet sensor itself. So in this Ask Hackaday, we’re going to make the case for why you could be using a tablet-like device for capturing user input or doing handwriting recognition, and then we’re going to ask if you know of any good DIY tablet designs to make it work.
Continue reading “Ask Hackaday: DIY Handwriting Recognition”
[Aykut Çelik] uses some strong words to describe how he feels about his VW Polo’s current radio set-up. Words like, “useless,” are bandied about. What is a modern man supposed to do with a car that doesn’t have built-in navigation or Bluetooth connectivity with phones? Listen to the radio? There are actual (mostly) self driving cars on the road now. No, [Aykut] moves forward, not backwards.
To fix this horrendous shortcoming in his car’s feature package, he set out to install a tablet in the dash. His blog write-up undersells the amount of work that went into the project, but the video after the break rectifies this misunderstanding. He begins by covering the back of a face-down Samsung tablet with a large sheet of plastic film. Next he lays a sheet of fiberglass over the tablet and paints it with epoxy until it has satisfactorily clung to the back of the casing. Afterwards comes quite a bit of work fitting an off-the-shelf panel display mount to the non-standard hardware. He eventually takes it to a local shop which does the final fitting on the contraption.
The electronics are a hodgepodge of needed parts: An amplifier, to replace the one that was attached to the useless husk of the prior radio set; a CAN shield for an Arduino, so that he could still use the steering wheel buttons; and a Bluetooth shield, so that the Arduino could talk to the tablet. Quite a bit of hacking happened, and the resulting software is on GitHub.
The final assembly went together well. While it’s no Tesla console. It does get over the air updates whenever he feels like writing them. [Aykut] moves forward with the times.
Continue reading “Fight That Tesla Envy With A Tablet Dash For Your Car”
We’ve probably all taken a look at the rash of cheap Intel-Atom-based tablet computers and wondered whether therein lies an inexpensive route to a portable PC. Such limited hardware laden down with a full-fat Windows installation fails to shine, but maybe if we could get a higher-performance OS on there it could be a useful piece of kit.
[donothingloop] has an Intel tablet, a TrekStore Wintron 7, bought for the princely sum of $60. Windows 10 didn’t excite him, so he decided to put Ubuntu on it, or more specifically to put Ubuntu on an SD card to try it on the Wintron before overwriting the Windows installation. His problem with that was a bug in the Baytrail Atom chipset which limits the speed of SD card access and made Ubuntu very slow, and in trying to fix the speed issue he managed to disable a setting in the BIOS which had the effect of bricking the machine. A show-stopper when the BIOS is in a tiny SPI Flash chip and can’t be wiped or restored.
What followed was an epic of desoldering the BIOS chip and reflashing it, though that description makes the process sound deceptively easy. The specification says it is a 1.8V device, so after attempts to flash it using an ESP8266 and then a home-made level-shifter failed, he was stumped. With nothing but a cheap tablet to lose, he tried the chip in a 3.3V programmer, and to his amazement despite the significant overvoltage, it survived. Resoldering the chip to the motherboard presented him with a working tablet that would live to fight another day.
We’d have said that this work might reside in the “Don’t try this at home” category, but since Hackaday readers are exactly the kind of people who do try this kind of thing at home it’s interesting and reassuring to see that it can be done, and to see how someone else did it. A tablet that can be bricked through a mere BIOS setting though is something a manufacturer should be ashamed of.
We like unbricking stories here at Hackaday, something about winning against the odds appeals to us. In the past we’ve covered Blu-ray drives crippled by dodgy DRM and routers rescued with a Raspberry Pi, but the crown has to be taken by the phone rescued with a resistor made using paperclips and pencil lead.
Everyone’s got an unused or even quasi-broken tablet lying around these days. [sairuk] has three kids, and somehow ended up with three broken tablets in short order. We’re not saying that correlation implies causality…
The digitizers were shattered, and since they were relatively cheap tablets to begin with, [sairuk] started thinking what could be done with a tablet that doesn’t have touch sensing anymore. He tried making an e-book reader for his kids, but somehow the idea of a MAME “cablet” (get it?) won out in the end. We’re not surprised: simple woodworking, gaming, and electronic hacking. What’s not to love?
This writeup goes into a lot more detail, so check that out too. He and his sons built up cardboard prototypes first (we love cardboard!) and then transferred their plans over to wood for the final “rough cut”. A PS1 controller reads out the joystick and buttons, and a PS1 -> USB adapter plus a USB-OTG cable connects that to the tablet. They also removed the batteries and built in a permanent power supply. Everything is simple and cheap, but the results are still impressive. Although they claim their build isn’t finished to the utmost, it looks pretty darn good to us.
We’re all frackers, so it’s satisfying to see a “junk” tablet put to good use. We’re wondering what [sairuk] is going to do with his other two tablets — we’ve got a suggestion for what he should do if he had twenty kids.
Continue reading “Broken Android Tablet Mini-MAME Cabinet”