Touch screen monitor OR Tablet PC?

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27 Jan 2013 08:30 - 27 Jan 2013 08:34 #29177 by birchy
I'm converting a Warco WM16 desktop milling machine to CNC. I currently have LinuxCNC (ubuntu 10.04 version) installed on an old desktop PC and am testing with a standard VGA monitor. For the finished project, I'd like to utilise touch screen control rather than using the bulky monitor and mouse/keyboard.

Can anyone recommend a touch screen monitor that's around 7" to 10" and not too expensive? Or maybe I could use one of those Chinese epad/apad android tablets that are readily available on ebay? Or perhaps some other HMI?

I'm open to all suggestions...
Last edit: 27 Jan 2013 08:34 by birchy.

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27 Jan 2013 14:14 #29182 by danemc
i guess you can root a tablet and ssh into the machine over wifi but the ultra cheap tablets have resistive touch screens not capacitive and aren't as good. also the firmware may suck. there are affordable resistive or optical dual touch monitors out there but they are much larger than 7-10" you may be able to find a panel only for some application and use lvds for video but i don't know if you'll find something with a digitizer that will be easy to hook up unless it's for a kiosk or atm machine. for a 10 point capacitive multi touch monitor like most tablets have you are looking at way more than the cost of a good tablet.

optical touch monitors are ok but not as good as capacitive like on a tablet. depending on the method they use it may need some pressure to read if it's frustrated internal reflection but i don't know if any production monitors use that. or it may read before there is any contact is made with several of the other optical technologies.

let us know what your budget is and we'll toss around ideas. optical touch panels are in the realm of what can be home made i just haven't seen the software for it in linux though i'm sure it exists.

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28 Jan 2013 01:47 - 28 Jan 2013 01:48 #29191 by birchy
Well I don't want to spend a lot of money as I can't justify spending £300 on a monitor for a £1000 project. Worst case, I'll use a small LCD or TFT monitor and keep the mouse and keyboard.

I've just had a play with VNC and have managed to get a remote desktop by logging in via SSH with public key (which I had already setup for uploading gcode and other files). The main issue with using remote desktop is that my WiFi card plays havoc with the latency, so I have to disable the wifi driver whenever Axis is running (see my thread HERE ).

Something like this 10.1" Capacitive Android 4.1 Tablet with HDMI would seem like an ideal candidate at only £56. But I don't know if it could be setup to control the LinuxCNC PC? The tablet has a HDMI slot, a Mini USB slot and Bluetooth connectivity. Could I use one of those to connect to (and control) the PC? What about using Bluetooth to get a connection and then use VNC? Is that even possible?
Last edit: 28 Jan 2013 01:48 by birchy.

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28 Jan 2013 02:16 #29193 by danemc
that's a great deal but it might not be the best tablet. the screen isn't high resolution and I'll bet the touch panel is less than stellar, the processor looks good, it has a Mali gpu so its either standard ARM or a Samsung die which would make it great (apple uses Samsung dies they tend to lead the way in ARM cpus though Qualcomm gives them stiff competition). unless you want to gut it and see what you can do to interface with the digitizer you'll need some kind of WiFi. does Ethernet mess with the latency? you could use a WiFi router in client mode to ssh or vnc into the machine. many routers can accept Linux based 3rd party firmware if they don't have client mode available in stock form. I use dd-wrt on several routers at home.

there may be touch screens available for car installs or hobby use. hopefully one can be found with a USB interface.

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28 Jan 2013 02:27 #29195 by birchy
How about using a Mini USB to RJ45 adaptor? I see they have them for around £5 on eBay. Assuming I could then link the Tablet direct to the LinuxCNC PC using the LAN cable (without going through a router), I should be able to control the PC using VNC. Does that sound feasible?

As far as tablets are concerned, I don't really need any fantastic specifications as it will basically be used as a touch screen monitor. Although I'm fairly savvy regarding computers and hardware, I'm a complete novice regarding anything touch screen...hence all the questions...

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28 Jan 2013 03:09 - 28 Jan 2013 03:22 #29199 by danemc
android can be weird. the kernel is pre compiled and it doesn't have any kind of package manager for drivers. only an apk installer for applications. I don't know if any android tablets will support network connections over micro USB. its only recently that they support host mode over USB and that uses a USB otg (USB on the go) protocol and only works with supported devices. I've only seen it done with memory cards and some DSLR cameras with the use of special applications. android does have terminal access through USB via the android debugger but that's to control the device not the other way around. search play.google.com to find apps. maybe there is one that allows either ssh or vnc over USB. I'm not really sure.

search eBay for touch screens for automotive installs.

edit: maybe you can get network connections over bluetooth easier than usb as weird as that sounds it seems from my experience that it's more likely to be supported. you can get a small usb BT dongle relatively cheap.
Last edit: 28 Jan 2013 03:22 by danemc.

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28 Jan 2013 03:55 - 28 Jan 2013 06:36 #29200 by birchy
Hmmm. Plenty to think about there. TBH, I was also wondering if I could buy one of those Android tablets but then install a Linux distro on it instead. At the end of the day, it's just a portable PC like a netbook/laptop. Or is it??

EDIT:
OK, so I've just experimented with VNC by connecting a Toshiba Netbook (running Linux Mint Debian Edition) directly to the LinuxCNC PC with a crossover Ethernet cable and performance was pretty poor. It also increased my latency by nearly 100%, so that rules out using anything connected to the Ethernet port.

So now I need to look for anything that can connect to the VGA...which will most likely end up being a £200+ touch screen monitor. :(
Last edit: 28 Jan 2013 06:36 by birchy.

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28 Jan 2013 06:34 #29206 by andypugh

birchy wrote: Can anyone recommend a touch screen monitor that's around 7" to 10" and not too expensive?

Resolution might be a problem, try setting your current monitor to the resolution of a small touchscreen and see how things work out.
It can be very annoying to find that the "OK" button of stepconf is off the bottom of the screen.
www.ebay.co.uk/itm/120941209900 would be ideal for you, except for the postage.

I have seen a video somewhere of someone controlling their CNC with a tablet. I wonder if I can find the link…
I am pretty sure they were using VNC or something similar.
<after looking for quite a while, I can't find it>

There is also this, but I can't find any details:

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28 Jan 2013 06:36 #29207 by danemc
well there are Linux installs you can do but I'm fairly sure it runs in a VM of some sort. even if it runs off the existing kernel its still not quite as capable as a full Linux disrto. the hardware on portable devices is largely proprietary and is supported by vendor supplied precompiled blobs. even with android sources you might not get full blown usb host support. the kernel may still detect connected devices but may not be able to do anything with it. android devices aren't as open as they want you to think. and the best bet for android is to get a nexus device as the development usually goes deeper. the boot sector and drivers and internal hardware varies widely from different android devices. its not like Linux where you choose between grub and lilo to boot the kernel and the rest is flexible. some things take some reverse engineering on android and the boot sector needs to be right for the hardware and the ROM.

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28 Jan 2013 06:49 - 28 Jan 2013 07:10 #29208 by birchy
As per the edit to my previous post, I experimented with VNC over Ethernet. Performance was fairly poor and latency nearly doubled. I have similar issues with my WiFi card, so have to disable it when running Axis. So that basically rules out anything VNC based unless I can use USB or Bluetooth...but I suspect that they won't be any better.

So connection to VGA is probably going to be the only satisfactory solution, which brings me back to touch screen monitors. I will also investigate industrial HMIs as I work in electrical engineering, but they're usually premium prices and a standard touch screen monitor will probably be cheaper.


EDIT:
Some tablets have an HDMI port. Is that purely for output to a monitor or could it be used as an INPUT? VGA to HDMI converter leads are available but I can't help wondering if something would fry if I was to connect the PC VGA to a tablet HDMI?


Maybe one of these monitors? www.ebay.co.uk/itm/111001870543
Last edit: 28 Jan 2013 07:10 by birchy.

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