General musing... making your own tablet? - Page 1
Forum section: electronics / projects

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 07, 2023, 12:58:51 am
content: Has any of you tried to make their own tablet, and if so, could you share some details?Beside the "fun" factor, the idea is to make something really custom, with the hardware you picked, and most of all, running the software that is entirely under your control.Of course, the big challenge is making it reasonably thin (doesn't have to be as thin as the commercial ones, but ideally no more than 10-12 mm) and reasonably light. About the thickness, it could be made pretty thin (just a few mm) for most of the display area and have a bit chunkier part at the bottom maybe for holding the hardware that requires more room.Another challenge is thermal management. Might require custom heatsinks. Ideally no fan. The most obvious approach would be to pick some SBC, ideally one that is not too thick (often due to the presence of either an Ethernet port or stacked USB ports.) I have a couple SBCs lying around, but none that would really fit the bill IMO, although maybe workable. Otherwise I have a couple IPS panels with a touch panel.Really just some weekend musing, I'm a bit torn between "fun project" and "total waste of time".

author: moffy
author_rank: Super Contributor
timestamp: October 07, 2023, 01:55:33 am
content: Perhaps a developer friendly linux tablet?https://www.zdnet.com/article/this-updated-linux-based-tablet-has-been-through-a-complete-redesign/

author: themadhippy
author_rank: Super Contributor
timestamp: October 07, 2023, 02:09:20 am
content: Quoteyea,a few times, just boil up a pound of sugar with a tin of condense milk and a generous half block of butterQuoteyep,getting the set point is critical or it wont set properly

author: rstofer
author_rank: Super Contributor
timestamp: October 07, 2023, 02:29:14 am
content: There are many ARM CPU/display combos around. Just box one up and write the OS...https://www.digikey.com/en/products/detail/stmicroelectronics/STM32F469I-DISCO/5428811If I were doing this, I would start with something like a Raspberry Pi because the OS is already written. A bit of a power hog...

author: beanflying
author_rank: Super Contributor
timestamp: October 07, 2023, 03:26:42 am
content: Of course it is a total waste of time but since when has that stopped most of us in the pastThermal management on any of the more modern ARM sbc's is becoming a major issue and frankly a lot of the PCB's regardless of manufacturer are crap when it comes to considering that, with components taller than the SOC but close to it limiting the size or needing complex mechanical solutions. Some of the dumbass solutions include supplying 3mm+ thick thermal pads to the heatsink on some Alix onesAlmost NONE of the mid to low end boards have mounting screws for the sink so it is likely 0.1 or 0.2mm tape or you need to make a very custom one cutting around some components to use the PCB mounting screw holes.If you do decide to go ahead with it a pitfall that has come up recently is some screens do not do the handshaking properly so the SOC can't identify what it is so you can finish up with a blank screen. So Screen selection try and base it on known compatibility. Possible this could be worked around in software but avoid it if you can.LiPo's are fairly simple to source as 1S but I would be tempted to look for an existing solution to kiss at least a little.Bunch of recent processors out there and even broader kernel support is getting there for some of the alternate ARM options. Allwinner be more careful but the more recent ones are A LOT better than even a year or two ago, Rockchip is really solid. Insert Fanboy option of Broadcom or die about nowWorth a consideration as all the ports lay flat on the board.http://www.orangepi.org/html/hardWare/computerAndMicrocontrollers/details/Orange-Pi-Zero-2W.htmlThat same processor/PMIC/wifi solution I have a couple of on the Zero3 boards and are running Ubuntu desktop really solidly. I spent a bit of time running it as a desktop and it handled that well.$0.02 worth of thought but now the weeding needs attention

author: RoGeorge
author_rank: Super Contributor
timestamp: October 07, 2023, 03:31:21 am
content: 3 dudes started already, by making the display.Quantum Dots (Nobel Prize 2023) - Periodic Table of VideosPeriodic Videos

author: moffy
author_rank: Super Contributor
timestamp: October 07, 2023, 05:34:25 am
content: Quote from: RoGeorge on October 07, 2023, 03:31:21 amFascinating video, first real explanation of quantum dots that I have seen and understood. Love the first guy's hair, and one of the Nobel prize winners used to work at Bell labs. How much technology and fundamental physics can be traced back to that organisation.

author: moffy
author_rank: Super Contributor
timestamp: October 07, 2023, 11:25:51 am
content: Nearly there:

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 07, 2023, 08:29:44 pm
content: Quote from: RoGeorge on October 07, 2023, 03:31:21 amEveryting quantum ought to be fascinating.

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 07, 2023, 09:28:28 pm
content: Quote from: beanflying on October 07, 2023, 03:26:42 amYep, absolutely. And in a confined environment like a relatively thin enclosure, heat dissipation becomes a real challenge using those SBCs, unless you stick to underpowered SoCs. But the idea here - if it was not obvious probably - is to make something on par with a current commercial Android tablet, something like that, in terms of CPU performance and RAM size. So that would probably require a custom heatsink, unless you can find something off-the-shelf that fits the SBC (and in this case that will probably require a fan to be effective enough.)Likewise, for the display that would be something from 10" to 13", Full HD (or better, but FHD would already do the trick here.)Quote from: beanflying on October 07, 2023, 03:26:42 amYes, good point. To minimize power consumption and the number of boards, ideally that would be a direct connection to the panel rather than go via HDMI, use a HDMI controller board to drive the panel, etc.The easiest to find panels for this have an eDP interface, so you're often stuck with using an external controller board, although a few (very few) off-the-shelf SBCs have an eDP interface on board. That's the case for one of the SBCs I have, problem of course is to figure out how to enable video output on eDP.Quote from: beanflying on October 07, 2023, 03:26:42 amYeah, the battery side of things is not really a big issue, but still requires some custom stuff as no SBC that I know of (there may be some though?) can be directly powered by a LiPo battery (and ideally handle battery charging and SoC estimation), so that's something you'd have to design, along with a boost converter as most SBCs take either 5V or 12V.Quote from: beanflying on October 07, 2023, 03:26:42 amAs long as Linux support is good, that should be fine. Most SBCs have decent Linux support these days. Of course the devil's in the details, and sometimes some hardware features are not fully supported and may never be as often the documentation for the hardware is either limited or non-existent.Ideally, the whole point would also be to be able to run Android apps, but either with an AOSP distribution of Android (that supports the hardware well, some SBCs come with one but they often have various issues), or possibly using an Android emulator on Linux - does anyone know of something like that which works well?Quote from: beanflying on October 07, 2023, 03:26:42 amYes, as I said the thickness of the SBC matters here and many are chunky. Sure the "zero" type of SBCs are lot more adapted to this, but they are usually much less powerful as well.The Khadas VIM4 doesn't look too bad for this:https://www.khadas.com/vim4Otherwise, yes I've seen a number of such projects on YT, so that's certainly not particularly original, but most of what I've seen more or less sucks.Now a ready-made off-the-shelf open-source tablet, with performance again on par with current commercial tablets, would be cool. (Yes I've seen a couple open-source tablets, but usually rather underpowered.)

author: nctnico
author_rank: Super Contributor
timestamp: October 07, 2023, 09:33:05 pm
content: Seems doable. Take an aluminium base plate (say 2mm) that serves as heatsink + mechanical stabiliser, a touchscreen panel and sandwhich a custom board + batteries between the panel and the base plate. Using a couple of USB-C ports for interfacing and charging and you should be able to get into the 15mm ballpark. Forget about RJ45; these connectors are typically way too high.

author: ejeffrey
author_rank: Super Contributor
timestamp: October 08, 2023, 01:25:44 am
content: The rasperry pi CM4 is a pretty good form factor for this and it's got a pretty good selection of display and IO, and while it has to stack on a base board, that lets you customize what you need without any bulky connectors you don't need. It's not the most powerful processor around, a Celeron class x86 SBC in the same form factor would be pretty awesome but I haven't seen any.

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 09, 2023, 07:43:51 pm
content: Using an aluminium plate and a CM4 would work I think. Said plate could probably serve as the back of the enclosure. Just wondering whether it wouldn't get too hot to the touch when the CPU is under full load, even if the plate's area is large (a bit larger than the display panel which would be at least 10". Additionally, I hope there will be a CM5 with the processing power of the RPi5. That would be better.Having directly an eDP port would be great as well, as I mentioned. I've seen it rarely on SBCs. I actually have one which has an eDP connector and a M.2 socket! It's this:https://www.friendlyelec.com/index.php?route=product/product&product_id=225It's a few years old now, but still decent - it has a RK3399. One issue with it is that it heats up like crazy, at least with the provided heatsink and no fan. But better cooling should probably help that quite a bit. I haven't tried the eDP output yet. I had a bit of a hard time finding the right cable (eDP - eDP, most eDP cables out there have a classic eDP connector on one end for the display panel, and something else on the other end.)

author: beanflying
author_rank: Super Contributor
timestamp: October 10, 2023, 05:58:07 am
content: Anything with a CM4/5 board and base is going to be fat even if you get to removing LAN and Double stacked or vertical USB's.While this still board has some teething issues depending on the OS (released about a month ago) with some connector shaving and removal could get you a more modern Rockchip and edp, emmc and m.2 plus other bits.http://www.orangepi.org/html/hardWare/computerAndMicrocontrollers/details/Orange-Pi-3B.htmlIt has edp or hdmi so pick your poison I guess for a display.Drop the LAN port, replace the dual stacked USB's gets you to just under 12mm thick keeping the eMMC and M.2 options along with the SD slot. Dieting further would take some more work. Copper plate is just a cutdown of the actual heatsink I used on mine but would work to transfer heat to a case.Spent 1/2 a beer not thinking very hard about this at all

author: Doctorandus_P
author_rank: Super Contributor
timestamp: October 10, 2023, 05:12:18 pm
content: I'm interested in an affordable tablet that runs Linux. The pinetabs are not acceptable to me because of a too low resolution. The absolute minimum for me would be 1920x1080 but preferably something like 2560 pixels high. I am not aware of any standard product you can buy for a reasonable price (around EUR300, maybe upto EUR400).I'm thinking about DIY-ing something. Somewhere along:* A "portable monitor" (Maybe remove the plastic back).* Some Linux board. (Maybe Odroid).* Whole lot of 18650 cells (I don't care about thickness, Even 30mm or so would be just fine for me).* A battery charging solution.Making a custom case is no problem for me. I'd slap together some aluminium tubings around the outside and solder them together with an Alu / Si solder alloy. If you can get the surface area, then a 2 part epoxy glue is also usable.The biggest challenges for me is to find a "portable monitor" with a touch screen that is Linux compatible and the electronics around the batteries (both for charging and power delivery to the Linux SBC and the monitor.There are also some similar projects documented on Hackaday. See for example the article below.https://hackaday.com/2020/08/25/checking-in-on-the-damn-linux-tablet-one/

author: Siwastaja
author_rank: Super Contributor
timestamp: October 10, 2023, 06:05:48 pm
content: Don't forget those magical graphite-based thermal pad materials that are significantly more thermally conductive than any metal (even copper/silver), but only come in thin sheets, and are only that conductive sideways. Pretty interesting stuff still if you have to spread heat over larger area and can't afford the thickness/weight of a 2-3mm aluminum plate.

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 10, 2023, 06:52:48 pm
content: Quote from: Siwastaja on October 10, 2023, 06:05:48 pmWell, these are meant to replace thermal paste with better results but I'm not sure I get what you mean? Thermal pads are not meant to act as heatsinks. Just maybe you may get better thermal dissipation with a thin plate if you use this kind of thermal pad instead of thermal paste, but I'm not sure that makes that big of a difference either.

author: beanflying
author_rank: Super Contributor
timestamp: October 11, 2023, 12:09:09 am
content: Quote from: Doctorandus_P on October 10, 2023, 05:12:18 pmFor weight, thickness, energy density and just general tabletising I would avoid 18650's in preference to likely two flat 1S LiPo's.For a monitor option this one I got a while ago works greateBay auction: #155256464964I am in the process of putting this into one of my Coffee Roasters. One of the major pluses is it has 6 actual screws holding the rear more part of the case to the bezel and screen so removing it then adding a new rear case or mounting it is a simple thing. In the case of using the HDMI for me that is recessed inside the form factor making for a clean finish.Interesting I was about to strip out an ancient tablet PC I used for years on that roaster and it was 18mm thick for its nominal 10" size.

author: Siwastaja
author_rank: Super Contributor
timestamp: October 12, 2023, 05:19:19 am
content: Quote from: SiliconWizard on October 10, 2023, 06:52:48 pmExcept that even Digikey understands to list "heatsink" as one usage category for thermal pads in their parametric search! I mean this stuff:https://industrial.panasonic.com/cdbs/www-data/pdf/AYA0000/AYA0000C27.pdfSee the thermal conductivity which exceeds that of copper and thus acts as a heatsink by very definition, spreading heat and dissipating it over larger area within a case as a bare product, or glued into plastic casing so that the case itself acts as a heatsink over larger area, which is very much desirable since plastics have poor thermal conductivity so you need to compensate by using larger part of the case to do it.Sadly, apparently this stuff can't be manufactured in large thicknesses (it seems thermal conductivity goes down as thickness goes up, so they rather offer a constant thermal conduction regardless of thickness). A 2mm aluminum plate will win a 0.1mm pyrolytic graphite sheet, but 0.5mm aluminum plate definitely not, so when you need a modest amount of heatsinking, PGS would be a very lightweight and thin solution.