Des_Zac
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Re: Tablet.

Sun Aug 07, 2011 2:44 am

I know this is on a lot of peoples minds and I wanted to make a forum for us to discuss it. I already know that this is by far one of the easiest things to make with this but there are a few concerns I have that I wanted to see if people could work together to solve with me. Here are the main concerns.

We need to find a cheap touchscreen monitor, multi-touch compatable, usb POWERED, and has room for the R-Pi and battery in it. It needs to be about 7"-10" and not need any other wires to power it.

We need to find a battery that we can attach to the R-Pi through its DC port (I think that's what you'd call it) Since the R-Pi will take barely any power the only real thing we have to worry about is the monitors power consumption.

We need to find a way to incorporate two small speakers inside of the Screen.

We need to have at least one external USB so people can attach their keyboard, usb hub, mouse, etc.

This is all I could think of at the time of posting but if you can think of anything else please respond... I want this to be a project we can all do and have a tablet that runs a real OS that doesn't cost as much as most ridiculous tablets are nowadays.

Also, (this is for the Devs) could you sell a decal whenever the logo is established that we can spraypaint on the back of the Raspberry Tablet? That way we can show off that it is Raspberry Pi inside.

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abishur
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Re: Tablet.

Sun Aug 07, 2011 3:21 am

I like the idea of a r-pi being turned into a tablet. One other thing that would need to be incorporated is a means for charging the battery. Namely, a autoswitching DC->DC device that would float charge the batteries and run the device while it is plugged. You'd think it wouldn't be too hard to find seeing as how laptops and cellphones and kindles and gameboys and so forth and so on ALL have this capability, but so far I've only seen one thing that does this and it cost around $50 dollars. To be fair though, I haven't spent a lot of time on the subject.
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ShiftPlusOne
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Re: Tablet.

Sun Aug 07, 2011 3:30 am

http://www.lilliput.cn/productusb.html
one of those will set you back about $150-$200 and uses about 3W.

The speakers are already included, but it would take some creative hacking to get a usb port and a battery in there.

AmyS3
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Re: Tablet.

Sun Aug 07, 2011 3:35 am

ive seen some chaep tablets on ebay as well.
running android with around 700Mhz, priced around 50-60 GBP...
they mainly use the via arm chips. and have a screen size of 7".
but i still like to see a raspi tablet ^^ maybe just buy a damn cheap tablet of the bay and replace the internals with a raspi.. ?

Des_Zac
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Re: Tablet.

Sun Aug 07, 2011 3:36 am

Quote from abishur on August 7, 2011, 04:21
I like the idea of a r-pi being turned into a tablet. One other thing that would need to be incorporated is a means for charging the battery. Namely, a autoswitching DC->DC device that would float charge the batteries and run the device while it is plugged. You'd think it wouldn't be too hard to find seeing as how laptops and cellphones and kindles and gameboys and so forth and so on ALL have this capability, but so far I've only seen one thing that does this and it cost around $50 dollars. To be fair though, I haven't spent a lot of time on the subject.

Where can I get the one that's $50?

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Re: Tablet.

Sun Aug 07, 2011 3:43 am

Also, I am pretty sure something like this will use 2 usb ports in order to get a high enough current. Since an r-pi will only have 2 usb ports, I don't see how you'd get an external usb port. Perhaps bluetooth and wireless keyboard/mouse would make more sense.

Des_Zac
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Re: Tablet.

Sun Aug 07, 2011 3:55 am

Or I could use a usb strip, and I've seen Touch Screen monitors that are only 1 usb wire, like this one http://www.amazon.com/gp/produ.....HHC9CNZFHR and some others I've seen.

AmyS3
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Re: Tablet.

Sun Aug 07, 2011 3:57 am

you can probably deliver the needed current from a sepperate 5V regulator connected to the battery itself.. and mabe switched by an gpio from the raspi so it want suck out the battery if the raspi is off..

Des_Zac
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Re: Tablet.

Sun Aug 07, 2011 4:13 am

Um sorry but I don't understand anything you just said Amy, caould you please explain it to me, I don't know what you mean by a regulator connected to the battery or what a gpio is, sorry.

AmyS3
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Re: Tablet.

Sun Aug 07, 2011 4:36 am

ok.
the monitor needs 5V so you have to give it 5V which you can get from the batteries.
the easiest way would be (if the batteries deliver more than 5V) that you connect a linear regulator like the L7805 http://uk.mouser.com/ProductDe.....fc%3d, or more of them depending on the current the monitor needs, to the battery and the power lines of the monitor.
since the monitor is going to be a usb type you have to connet the regulator to the + and - lines of the usb cable.
there are existing cabels to slave in power to a usb device.
you could then add a transistor or rather a mosfet between the regulator and the batteries which will allow you to "swich" the regulator/s on and of.
those transistors of fet´s can be triggert by an gpio from the raspi. a gpio is a input/output pin on the raspi board which can be set to high or low (on/off) by some kind of software.

hope that helps..

Des_Zac
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Re: Tablet.

Sun Aug 07, 2011 4:41 am

Okay, I understand a little better now, but what I think we should do is have us, (As the R-Pi Community) Compile a list of parts that someone would need to make this, then someone with experience, (Definitely not me) make a picture accompanied tutorial on how to put it together.

AmyS3
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Re: Tablet.

Sun Aug 07, 2011 4:47 am

you can take a look at my uav project to get an idea for a good structure.
-> http://www.raspberrypi.org/?pa.....&t=82

Des_Zac
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Re: Tablet.

Sun Aug 07, 2011 4:50 am

The only problem that I don't understand is how to connect the battery to the R-Pi, could someone explain that please?

AmyS3
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Re: Tablet.

Sun Aug 07, 2011 4:54 am

first of all you have to decide which kind of battery you want to use..
which type: ni-mh, li-io, li-po.. ect
what voltage and which current...

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Re: Tablet.

Sun Aug 07, 2011 4:57 am

Quote from Des_Zac on August 7, 2011, 04:55
Or I could use a usb strip, and I've seen Touch Screen monitors that are only 1 usb wire, like this one http://www.amazon.com/gp/produ.....HHC9CNZFHR and some others I've seen.
ah cool

Des_Zac
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Re: Tablet.

Sun Aug 07, 2011 4:58 am

I know nothing about batterys, but the one that best balances price/length of battery life

AmyS3
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Re: Tablet.

Sun Aug 07, 2011 5:04 am

that would be li-po batteries.. but that gives some headache for the chargin circuit while the device is running..
i have some problems with that as well..
but since you dont want to send you´re tablet around the world on its own you can use a permanent connected balancer for the li-po´s so the cells don´t get unbalanced while you charge them.
but i would advise you to go on a little trip with google about charging li-po´s to get more insight about that matter...

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Lob0426
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Re: Tablet.

Sun Aug 07, 2011 11:37 pm

From the schematic it appears the raspi will have a pretty wide voltage input range (6 to 20 volts). If true that should not be problem. As to powering the USB, tearing down a powered hub and finding space for it should not be too much of a problem as long as it is small. Protecting the circuit with diodes and using resistors to have the right voltage into the hub also should not be difficult. Charging the LiPo batteries can be a problem, but I suggest you look at the radio control market and see if any of those chargers may be able to be hacked into the design. Of course you might also be able to just steal the components from a dead laptop or net top motherboard.
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AmyS3
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Re: Tablet.

Tue Aug 09, 2011 5:15 pm

if the raspi can be powered with 5V than i´ve got a solution for your power problem.
the circuit is not tested yet but im confident that it works.
see here: http://www.raspberrypi.org/?pa.....ostid-1276

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abishur
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Re: Tablet.

Tue Aug 09, 2011 7:33 pm

Actually, from what someone else was telling me the r-pi will not be able to be powered with 5V. The issue, as I understood it so take this with a grain of salt, was that you can't both be powered by 5V and provide power for a 5V USB as well. But you up the Voltage a little and it all works out (or so is my understanding)
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AmyS3
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Re: Tablet.

Tue Aug 09, 2011 7:49 pm

sure i can adjust the voltage but than i need to add a additional regulator to give some power to the monitor, since that one can not be powerd bz the raspi alone..
so the output would be 5V and 6V...
or did i miss something about the monitor?

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abishur
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Re: Tablet.

Tue Aug 09, 2011 8:06 pm

I guess worst case scenario, you could always put the appropriate resistor between the PS and the monitor... right? Oh, I think that's what you meant by "additional regulator". If you do go that route, it shouldn't be more than 50 cents more for the resistor right?
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AmyS3
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Re: Tablet.

Tue Aug 09, 2011 8:31 pm

well in generally yes... but a propper linear regulator would be more stable and efficient since you would loose the 1v as heat if you use a simple resistor..
a linear regulator which can provide enough current for the monitor would be around 1.25-1.50 pound.
but i send eben a text already and asked about the 5V input option for the raspi.

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Re: Tablet.

Mon Aug 22, 2011 8:58 pm

I would love to make a tablet out of my Rpi.
In fact I would like to make it a business tablet. The last successful mobile business OS (although a bit crappy) was WinMo 6.1. Everything from there on WinMo 6.5, WinPhone 7, Android, etc (even unfortunately including MeeGo) just seem inappropriate for business use.

Having a mobile device touch friendly vs touch oriented makes the difference. I want a device I can work with my fingers (sometimes a pen stylus works better) but having a device with all the bells and whistles means nothing when I want to view a document or spreadsheet on site and get just 3 lines of data on screen.
I mean come on guys. Having displays on mobile devices that go up to 800x600 just to view a movie is insane!!!

So I'm in to make a tablet out of Rpi. A tablet to be used as a business device.
Some pointers:
- Touch Screen: If I could find an "old" resistive touch screen it could be even better so that I can reuse my Diamond's stulys. I DON'T WANT capacitative or multi touch screen. If I could even reuse my Diamond's touch screen I would do so (don't have a clue about signaling though). Any screen big enough to hide Rpi's pcb behind would do.

- Battery pack: Maybe a homemade array of batteries to fit the size behind the Rpi. A simple charging circuit good enough to handle power switching when on batteries or charging.

- Enclosure: No fancy things. Just a tidy case to stuff all these things into. Taking into consideration that most likely Rpi will have connector at three sides of it, I will most likely place the pcb on a corner giving access to connectors on the two sides of the pcb and hardwiring the other. SD on the other hand is a bit tricky all by itself. Maybe placing Rpi with the connectors touching the screen would give access to the SD from the bottom of the "device".
(It would be very usefull to know if the connector sides are finalized by now for the production Rpi)
Keeping that in mind any battery with a thickness as much as the ethernet port would be no prob.

For any extra thoughts, I'll jump right in.

nghia
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Re: Tablet.

Sun Oct 02, 2011 6:29 am

Quote from abishur on August 7, 2011, 04:21
I like the idea of a r-pi being turned into a tablet. One other thing that would need to be incorporated is a means for charging the battery. Namely, a autoswitching DC->DC device that would float charge the batteries and run the device while it is plugged. You'd think it wouldn't be too hard to find seeing as how laptops and cellphones and kindles and gameboys and so forth and so on ALL have this capability, but so far I've only seen one thing that does this and it cost around $50 dollars. To be fair though, I haven't spent a lot of time on the subject.

Hi Abishur

Can you give us the link to this 50$ item?

Thanks
Nghia

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