Drive bay touchscreen

[Konrad]

I'm planning to build an ARM-based integrated hardware monitor, fan controller, light controller, etc. Basically a semi-permanent PC chassis feature, ideally with a glitzy "big" touchscreen covering all or most of a drive bay facing. Maybe some knobs and buttons, too, if there's enough space.

(I've discovered a few pre-made items of this sort, like the Aquaeros product line. Vastly overpriced. Really, really, vastly overpriced - especially since they break capabilities into modules and accessories which must be individually purchased. Too generic and simplified and powerless for what I want it to do, designed as a big-branded plug-n-play drop-in unit for wimps afraid to solder and code their own gear. Also, I want to put my hardware monitor where it belongs - meshed directly into the hardware - for it to have completely standalone and accurate and instant data, for it to not depend on the sloppy second-hand hearsay and latency of limited UEFI/BIOS and OS and USB-enumeration services. Kinda nice to see all your temps and how all your processor cores are loading before you even boot up an OS.)

Standard 5.25" drive bays are 5.25" (141mm) wide and 3.5" (83mm) high. I'd like a touchscreen no smaller than about 4" wide, no larger than about 6" wide. The PC chassis offers about 1" extra space on each side, plus several inches of height - I would just prefer a landscape-oriented screen which is visually roughly equivalent to the devices mounted in drive bays underneath - dimensions are not critical. A screen with at least VGA 640x480 sort of resolution. Nice, bright, capable of displaying the usual full rainbow of colours. Exact resolution, landscape/portrait orientation, aspect ratio, etc, are irrelevant since I'll just build whatever LCD interface controller I need to make it work.

Touchscreen technology is also unimportant, provided it responds to finger contact and doesn't require any tool or stylus to operate.

I was thinking cellphone or PDA screen, but it's very difficult to get dimensional specs beyond the standard "corner-to-corner" diagonal which is proudly marketed. Sadly, it's also kinda hard to buy a dead unit with an intact screen - it invariably dies before any other component, in practice even the best-protected of "large" smartphone screens seems to break before the battery flatlines.

I suppose I could always order a part from somewhere in Shenzen, but it seems like it shouldn't be too hard to find a broken/failed/blacklisted device with a good screen locally on the cheap, if I'm persistent.

So my question - since I already have a great little smartphone and really don't much care about the fancy bling bling built into all the latest/greatest new toys - can anyone recommend some mainstream devices out there which have touchscreens that fit my parameters?

[TheMainMan]

If you have someone you know with a US address, the Nokia Lumia 520 can be had new for $29.99 USD with no contract on Amazon.com (http://www.amazon.com/Nokia-Lumia-520-GoPhone-AT/dp/B00E45043A/ref=sr_1_1?ie=UTF8&qid=1418134638&sr=8-1&keywords=lumia+520&pebp=1418134640387). At 4" diagonal, it's on the small end of the range but they do come with fairly nice screens for the price.

[TLHarrell]

Cheap Android tablets can be had for ~$30-50 and would easily be capable of doing what you want with some additional hardware. Optionally, you could keep the tablet as a standalone unit and wirelessly poll the data.

[Konrad]

Oh, there will be wires. Everywhere.

4" diagonal is just too wee for what I tentatively call the Computer Chassis Control Panel (CCCP).
Great idea on the tablets, though, thanx!

[EDIT:
I've found this Raspberry Pi kit (http://www.sainsmart.com/raspberry-pi/7-inch-tft-lcd-monitor-for-raspberry-pi-touch-screen-driver-board-hdmi-vga-2av.html#customer-reviews) which fits my parameters almost exactly perfectly! 7" (165x100mm) 800x480 InnoLux AT070TN92 (https://www.olimex.com/Products/OLinuXino/A13/A13-LCD7-TS/resources/S700-AT070TN92.pdf) LCD/TFT with multi-contact non-stylus touchscreen, HDMI/VGA/2AV VS-TY2662-V1 (http://www.vslcd.com/Specification/VS-TY2662-V1.pdf) controller board, anti-glare & fingerprint-resistant surface coat, reasonable price (vs similar touchscreens, anyhow) with free (but slow) shipping to Canada. Integrated USB interfaces for whatever dark purpose I might conceive. A largish variety of glasstops and bezels commonly available for this particular display panel.
That problem solved, sorry to waste your time.]

But now I'm having a bit of a stumble on the most trivial issue:

I plan to light up an array of RGB LEDs, fully configurable via a colour-wheel sort of applet. Easy enough, each LED bank just needs to be controlled/powered by 3 or 4 PWM outputs, already plenty of PWM-capable IO pins available and more can always be ganged as needed through add-on PWM parts. But I am thwarted by the momentary-contact POWER (and RESET) switches - their LEDs need to instantly illuminate when switched, but PWM controllers invariably have a little bit of bootup delay. By "instantly" I mean with an imperceptible delay of, say, <10ms (arbitrary number). You press button, you see pretty colour-configurable light in button go on. So I think I need to wire their LEDs through a very fast-startup mcu part (like a TI MPS430?) and/or a very fast little bit of NVRAM (lol, to "instantly" cough up just a teeny tiny handful of 32-byte values, sadly). Is there a better approach without logic parts? Anyone done this before?

[TLHarrell]

Not sure about programming on the Pi, but can you set a default value for them to come on at before the rest of the UI is loaded up? I'm just learning this stuff myself with Arduino and some WS2812's.

[Konrad]

I've never worked with a Pi board, don't know the answer to that (yet).

I have worked with Cortex ARMs, I know of no such instant-boot option. Their bootloader takes a few milliseconds, their OS can take up to a few seconds more (depending on what hardware is present, what sorts of OS things start up). You can gain the appearance of an instant boot, just like with any smartphone or tablet, by leaving the thing running on standby. That requires a constant power source. A battery isn't impossible, but seems kinda involved for such a trivial feature. Perhaps I can leech a little +5VSB off the PSU, though I really don't know my ATX/APCI stuff, I don't know if the PSU will provide lots of +5VSB (rated for up to 4A/20W, although sleeping computer normally uses far less) or if it will deliver only exactly what the mobo BIOS reports is needed.

[x88x]

*dusts off keyboard*

Ok, let's see if I still remember how to do this 'forum' thing. :D

A-series ARM SBCs (Single Board Computers) like the Raspberry Pi are a very different (and IMO much more user-friendly) beast than uCs (micro Controllers) like the Arduino/ARM-M3/etc. Think of it less like a logic controller and more like another computer (albeit a very small, low-power, one). Most ARM SBCs are designed to run either Linux or Android. Noting, that, let's take a step back here and look at what exactly it is you're wanting to do.

Front end:
- 4-6" touch screen
- Video control/etc
- Status LEDs
- Physical button inputs

Back end:
- Interface with buttons for user input
- Touch screen input for user input
- Video screen for output
- LEDs for output
- Manipulate motherboard power controls
- Read temperature sensors
- Read other sensors maybe?

Fundamental features:
- Completely independent of host computer
- Controls host computer
- Instant (or near-instant) response to user controls

What this all boils down to is a ton of GPIO (General Purpose Input/Output) pins and a battery for the SBC.

What I would recommend is an always-on SBC controlling the host machine, that pulls power from the host PSU only when needed. Alternately, if you expect the host machine to remain off for long periods of time (say, several hours), then it might be a good idea to include a distinct power source for the SBC. Keeping the SBC online 24/7 would allow you to have instant response time for any actions, while keeping the whole system fairly simple and low-cost.

If you haven't purchased a Pi yet (or if you have and are flexible) I would highly recommend checking out the Olimex OLinuXino boards (https://www.olimex.com/Products/OLinuXino/open-source-hardware). Specifically, the A20-MICRO (https://www.olimex.com/Products/OLinuXino/A20/A20-OLinuXino-MICRO/open-source-hardware), A20-LIME (https://www.olimex.com/Products/OLinuXino/A20/A20-OLinuXino-LIME/open-source-hardware), or A20-LIME2 (https://www.olimex.com/Products/OLinuXino/A20/A20-OLinuXIno-LIME2/open-source-hardware) would be very well suited for your purposes. Personally, I would recommend the MICRO because even though it is twice the size, its GPIO pins are a much more workable 0.1" step pins (same as on the Pi and most breadboards) versus the 0.05" step pins on the LIME variants.

I would recommend these boards for two reasons:
1) They have a metric **** ton (technical term) of GPIO pins (160)
2) They have built in battery power circuitry. All you would need to do is get a compatible battery (they (https://www.olimex.com/Products/Power/BATTERY-LIPO1400mAh/) even (https://www.olimex.com/Products/Power/BATTERY-LIPO3000mAh/) sell (https://www.olimex.com/Products/Power/BATTERY-LIPO4400mAh/) some (https://www.olimex.com/Products/Power/BATTERY-LIPO6600mAh/)) and hook the board up to an appropriate voltage source (MICRO takes 6-16V, LIME takes 5V).

They also are way more powerful CPU/RAM than the Pi, which is handy. ;)

I have purchased from them before, and shipping to the US they're almost as fast as Amazon (seriously; it was something like 4 days from placing the order to it showing up on my doorstep, with standard shipping).



Forgot to mention; Olimex also has screens, if you're not locked into the one from SAIN SMART yet.
https://www.olimex.com/Products/OLinuXino/LCD/

[x88x]

Ooooh, I just had an awesome idea. Make the UI a web interface, accessible on the in-host screen via a browser in full screen, hook the SBC up to your network, and you can get all the info/control from any browser. :D

[Konrad]

I see that the LCD-OLinuXino-7TS (https://www.olimex.com/Products/OLinuXino/LCD/LCD-OLinuXino-7TS/open-source-hardware) also uses a AT070TN9X TFT LCD part, at roughly the same cost. The only dealbreaker on it is the resistive touchscreen, which likely requires a stylus. These screen kits may or may not be interchangeable, I guess I'll have to check specs for both of their interface/logic boards.

I never knew about Olimex, I like it, I like it a lot. Open source, documentation, support, wiki, community, all looks very promising. Most of my local rPi resources are crazy greybearded ham radio groups - cool stuff, but not the droids I'm looking for. Methinks that - if my fussy touchscreen issue can be resolved - I shall migrate over to A20 products. Mucho overkill, little project seems to be growing up fast, but more robust capabilities are always better, more GPIO (without more complexity) is damn good.

Maybe, yeah, basic LAN (and/or WIFI?) web interface. Perhaps some audio op-amps and on-screen digital equalizer, maybe. Password/security and "Reward if found" bootscreens. Options are limitless. But lemme focus on the essentials first (hardware/system monitor, fan/temp/pump control, light control, etc). The only problem (perhaps not a problem) I foresee with the largest Olimex board is PCB dimensions 142.24x82.55mm, just a teeny teeny bit larger than the drive bay plate mounted in front.

I still have a pair of Model B+ Rasperries. Pathetically slow and feeble little things. Edging a little closer to craigslist every day, lol.

[Konrad]

[Off-topic in my own post ... already modded my ZM1250 Platinum PSU (http://www.zalman.com/global/product/Product_Read.php?Idx=643) with some extra internal sensors, PWR_OK signals (and LED) to feed into my "CCCP", some minor thermal upgrades, a few kJs of MOV (with more LEDS!), etc. I plan to mate chassis+PSU+"CCCP" for many years of heavy use.]

[Off my own off-topic ... got any favourite op-amp parts or circuits to recommend? Shouldn't be too hard to shield and isolate from the rest of the beast, unless I'm using Big Watt tubes or something, lol. Standard 3.5mm audio output, primarily for a budget-audiophile-collection of 32-40 Ohm headphones.]

[Damn! I can also install a few-port LAN hub into a drivebay! And a power outlet bar along the bottom. I even have a nice little out-of-the-way place to velcro a Dollar Store flashlight for all those trips inside the PC, yeah that's how I roll.]

[x88x]

I see that the LCD-OLinuXino-7TS (https://www.olimex.com/Products/OLinuXino/LCD/LCD-OLinuXino-7TS/open-source-hardware) also uses a AT070TN9X TFT LCD part, at roughly the same cost. The only dealbreaker on it is the resistive touchscreen, which likely requires a stylus.

The one you linked should work just fine with an OLinuXino board. It looks like just a standard HDMI/VGA interface for video and USB for the touch screen. I'm not seeing anything on the product page for that screen saying whether it is resistive or capacitive though. In my experience, usually with components like these, unless they specify that they are capacitive they tend to be resistive.

And yeah, Olimex is pretty awesome. :D Check out their blog (http://olimex.wordpress.com/). It's basically a few Bulgarian hardware geeks who decided they wanted to start making their own stuff. Pretty neat people, and they do a lot of cool stuff with their business.

[Konrad]

I searched long and hard, combing every detail of every datasheet for touchscreen specs.

Then I clicked on the video right in my face (for the kit I found). Guy very obviously operating it with finger touch, no stylus. The Olimex page offers no counterpart video, although resistive touchscreen is specified - and according to all the wikis and online chatter I could find, small (ie, less than about 20") resistive touchscreens all require some sort of stylus.

[TheMainMan]

I'm pretty sure the 7" touchscreen in my head deck is resistive and I've never used a stylus with it. If I can remember I'll check if I can use it with an inanimate object when I head out to hockey in a couple of hours. I'm almost certain it's resistive and I've never used anything other than my finger on it before.

[x88x]

Yeah, you can use small resistive touch screen without a stylus. That rule of thumb probably originated from old resistive tech that was very inaccurate unless you were using a small, hard, point.

I have three small device with resistive touch screens: a Dell Axim x50v (c2004, 3.7"), a Nokia N900 (c2009, 3.5"), and a WinBook TW801 (c2014, 8"). The Axim definitely needs a stylus for any detailed work, but if the target area is larger than, say, 0.5" square, you're probably fine. The two newer devices have immensely better resistive touch technology (it actually took me a few hours of use to realize that the WinBook was resistive). With those, it's really more a matter of how small is the button versus how small is the thing you are using to the touch the screen.

The reason for the difference is the distance between the two layers of the touch screen sensor. With older sensor tech, like on the Axim, the layers were pretty far apart (I would estimate ~1-1.5mm). You can actually feel the top layer depress when you touch one. This caused the sensed "touch" area to be larger than the actual contact patch. Compare this with modern resistive sensors, like on the WinBook, and there is no discernible movement when you press down on the screen. Because of this, the sensed contact patch is (near as makes no difference) identical to the actual contact patch. Also because of this change in sensor tech, the amount of force required to activate the sensor is much less, so it is possible to get a much smaller contact patch with a soft, semi-pointed, object (say, a finger).

Long story short, I haven't used either of the screens you are looking at, but I would imagine that either would work fine for your application.

[TheMainMan]

I'm pretty sure the 7" touchscreen in my head deck is resistive and I've never used a stylus with it. If I can remember I'll check if I can use it with an inanimate object when I head out to hockey in a couple of hours. I'm almost certain it's resistive and I've never used anything other than my finger on it before.

I checked but forgot to post back with an update on Friday. It's definitely resistive as I was able to use the corner of a credit card to activate buttons. It was way more responsive to the credit card than it usually is with a finger but I'm not sure using a pointed object on the screen while driving is a good idea at all :D

Good luck with the screens, can't wait to see photos!

[Konrad]

Photos, seriously? Sure, I guess, once my parts start showing up and I can actually get my hands dirty instead of nebulously dreaming away on some obscure little online forum.

I decided on the non-Olimex screen kit because - even if it turns out to be suboptimal - it publishes hard specs on more of the details I consider important for this quest. Not my very first foray into ARM boards, but no need to add uncertainty to something new while still facing a learning curve.

My OS options are basically a linux, Android, or WinCE (er, actually WM2003SE/WM5, still got a "license" I can migrate off my ancient little Dell Axim X50v). I know my linux well enough to do everything I want, although at a glance it appears Android has more code resources available for my specific app (system monitors, colour wheels and ribbons, audio equalizers, clocks & calendars, etc). Time to break out my old C compiler, browse opensource libraries, and get to work.

[x88x]

Just a side note; if you need more specs on a particular cart from Olimex, try just asking them. They seem to be very responsive, and all of their hardware is OSH (Open Source Hardware), so they usually even have the schematics/PCB designs/etc published and linked on the product page.

[Konrad]

Alrighty lol, gonna go pure Olimex all the way. Easy enough to cancel my other order, the backordered kit wouldn't have shipped until after xmas season anyhow.

I've chosen 12mm antivandal-style switches (http://www.modmaker.co.uk/Mod-Making-Supplies/Switches/12mm-LED-Illuminated-Vandel-Proof-Switch-RED) for power and reset - shouldn't be too hard to mod them with 4-pin RGB LEDs, even if size constraints force me to use SMT components. Planning to use some tactile switches behind a suitable rubber 5-arrow button pad cut out of a dead remote, dozens to choose from at my local thrift store. Trying to find a few rotary switches (switch and knob) which match the beautiful volume control built into my Das Keyboard (http://www.daskeyboard.com/daskeyboard-4-professional/). Also trying to find some USB3 ports which are gold-plated and aren't that obnoxious "Pantone 300C Blue" - black or darkish grey would look much nicer, recommendations from official USB3.x spec be damned. Quality USB2 ports and 3.5mm audio connectors are easy enough to find.

I was thinking of putting a thin transparent bezel (a ring ~1mm wide, perhaps raised <1mm) around each front connector, paired with an LED to indicate whenever a device is actually plugged in and powered. Maybe a similar bezel around the touchscreen, although I'm not sure that would be workable - I don't want any touchscreen edge components/PCB to show through, and besides, such a thing might just look artlessly gaudy.

For me the electronics are trivial. Precision cutting and drilling and tapping (through thin burnished aluminum plates and some dense ABS chunks) would all be done by hand and might end up a little rough. Ha, perhaps I could interest TBCS metalworking mod-god Waynio with a small commission, eh?

But choice of suitable materials stumps me. Would glass bezels around the connectors chip too easily? Is a hardened glass available? Would plastic/acrylic bezels scratch and crack too easily? How and where would I obtain these things? Does somebody already sell parts of this sort? Alas, I have no real access to laser cutters and 3D printers at this time.

Alternately, I could just use plain little rectangular LEDs and pretty metal bezels. I do have ready access to theme-appropriate metal finishings like Carbonia, Black Oxide, Black Nickel, and Black Chrome.

[x88x]

Haha, didn't mean to push you into that. :P

For the glass, I know most (if not all) of the nice modern consumer electronics use some version of Corning Gorilla Glass. Not sure if that can be purchased by itself or not. Honestly though, for your application I think it'd be a bit overkill. Normal hardened glass would probably be fine (also not sure where you would get that, tbh).

Regarding availability of 3D printing, I've heard good things about services like shapeways (http://www.shapeways.com/).

[technotronix]

I'm planning to build an ARM-based integrated hardware monitor, fan controller, light controller, etc. Basically a semi-permanent PC chassis feature, ideally with a glitzy "big" touchscreen covering all or most of a drive bay facing. Maybe some knobs and buttons, too, if there's enough space.

(I've discovered a few pre-made items of this sort, like the Aquaeros product line. Vastly overpriced. Really, really, vastly overpriced - especially since they break capabilities into modules and accessories which must be individually purchased. Too generic and simplified and powerless for what I want it to do, designed as a big-branded plug-n-play drop-in unit for wimps afraid to solder and code their own gear. Also, I want to put my hardware monitor where it belongs - meshed directly into the hardware - for it to have completely standalone and accurate and instant data, for it to not depend on the sloppy second-hand hearsay and latency of limited UEFI/BIOS and OS and USB-enumeration services. Kinda nice to see all your temps and how all your processor cores are loading before you even boot up an OS.)

Standard 5.25" drive bays are 5.25" (141mm) wide and 3.5" (83mm) high. I'd like a touchscreen no smaller than about 4" wide, no larger than about 6" wide. The PC chassis offers about 1" extra space on each side, plus several inches of height - I would just prefer a landscape-oriented screen which is visually roughly equivalent to the devices mounted in drive bays underneath - dimensions are not critical. A screen with at least VGA 640x480 sort of resolution. Nice, bright, capable of displaying the usual full rainbow of colours. Exact resolution, landscape/portrait orientation, aspect ratio, etc, are irrelevant since I'll just build whatever LCD interface controller I need to make it work.

Touchscreen technology is also unimportant, provided it responds to finger contact and doesn't require any tool or stylus to operate.

I was thinking cellphone or PDA screen, but it's very difficult to get dimensional specs beyond the standard "corner-to-corner" diagonal which is proudly marketed. Sadly, it's also kinda hard to buy a dead unit with an intact screen - it invariably dies before any other component, in practice even the best-protected of "large" smartphone screens seems to break before the battery flatlines.

I suppose I could always order a part from somewhere in Shenzen, but it seems like it shouldn't be too hard to find a broken/failed/blacklisted device with a good screen locally on the cheap, if I'm persistent.

So my question - since I already have a great little smartphone and really don't much care about the fancy bling bling built into all the latest/greatest new toys - can anyone recommend some mainstream devices out there which have touchscreens that fit my parameters?


Hi Konrad,
Did you tried finding old device screen from ebay or amazon or you may also post your requirement on craigslist.org ?