External Display from an iPad LCD, Part 1

BuildIts in ProgressiPad Monitor
Last summer, Bayley, Sherry and I got a stack of iPad 3 LCD off ebay for $50 apiece.  These are 2048x1536 9.7" LCDs, and a cool thing about them is that they use a displayport interface internally.  This means you can splice the ribbon connector that comes with an LCD into a normal display port cable, add a backlight driver, and use the display with any computer.  This is a fairly straight forward and well documented.

My original plan was to build my own board and backlight driver.  After sitting on the LCD for over 6 months without making any progress, I decided to just get a premade breakout board and backlight driver from here for around $35.


This particular board has built in LED drivers for the backlight as well as adjustable brightness and USB power.  Unfortunately, at full brightness the assembly draws over an amp at 5V, meaning it can't be directly powered off USB.  Here's the board with the LCD working, powered off the bench supply:


When powered only off the USB port, half of the backlight turns off or flickers:



 Fortunately, the controller built into the board lets you adjust the backlight brightness.  I lowered the brightness to a level where brightness was still reasonable, but current draw dropped to around 600 mA.

I then looked up the datasheet for the backlight driver.  Here it is.  According to the datasheet, the current limit is set by a resistor according to a formula on page 11.  I found some appropriate SMD resistors for a current limit of 600 mA at MITERS, and replaced the stock resistors that came with the board.

Swapped resistors circled in red

This lowered the default brightness, and made current draw a bit more reasonable.  But 600 mA is still too much for a USB 2 device (which the board is), which is capped at 500 mA.  However USB 3, which my laptop has, can supply up to 900 mA to devices that identify to the computer as high power USB 3 devices.

To trick my computer into making the full USB 3 current available, I ran to Microcenter and bought the cheapest ($10) external USB 3 hard drive enclosure I could find.  I assumed that since it was listed as being able to power spinning HDD's (not just SSDs) just off the USB port, it would probably be a high power device.


Plugging it in and checking the device properties confirmed this, so I stripped the enclosure apart.  The electronics fortunately were extremely compact:


To leach power off the board, I just added jumpers between the LCD driver board and the power pins on the enclosure board.  


Yes, my LCD has a SATA port in it...

Here's the screen running only of a mini displayport and a USB port:


Building an enclosure will be wrapped up in part 2.

Comments from Blogger

wonsnot — June 08, 2014 at 02:27 AM
I think it would be awesome to make it touchscreen capable too, since the digitizer is relatively cheap as well.
Anonymous — June 08, 2014 at 04:32 PM
would it be possible to run it off of thunderbolt and have the retina powered by it as well?
Ali — June 10, 2014 at 11:18 AM
Do all i-devices use the DisplayPort interface? As-in, could I use this same method for a iPhone/iPod Touch display?
Jeff — June 11, 2014 at 12:38 AM
Very nice! Looking forward to part 2
Deisuke — June 11, 2014 at 12:46 AM
Definitely an interesting use of an iPad LCD, though with the cost and effort that went into this, you would have been better off just buying a second-hand monitor.
Ben Katz — June 11, 2014 at 12:47 AM
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Ben Katz — June 11, 2014 at 12:48 AM
Not really.... There is no such thing as a commercially available monitor with equal size, resolution, and portability.
Anonymous — June 11, 2014 at 11:26 AM
Some people just dont get the hacker mentality, i think this is an awesome example of someone who takes an idea and roles with it using what he has to hand. next time i get a broken ipad i may give this a shot myself.
Mattster — June 11, 2014 at 12:06 PM
Adafruit carries this display all setup and ready to use http://www.adafruit.com/products/1652 except they seem to be out of them
Anonymous — June 11, 2014 at 03:17 PM
The Adafruit one uses a separate power adapter to drive the display though...not sucking power from a USB port like this one.
Anonymous — June 11, 2014 at 06:02 PM
I have an iPad 1 that I would be willing to sacrifice to this. Do you think its screen would work?
Anonymous — June 11, 2014 at 09:40 PM
I think you would hate it.
Anonymous — July 02, 2014 at 09:45 PM
Hey I have a quick question. Could you draw the power from the thunderbolt port instead of the USB port? And get a USB hub back there so you could connect the driver to that? I'm just trying to figure out how to save that USB port and make it all run off of one thunderbolt port.
Anonymous — March 14, 2015 at 02:43 AM
Mình muốn thay man hinh ipad 4 cửa hàng có thể cho biết giá cho mình có phiền không thay màn hình ipad 4 giá bao nhiêu
Anonymous — January 20, 2016 at 07:25 PM
Hey, I have an old Ipad 1, which is nice, but hardware is outdated. The screen is super nice though. I also have an old Ipod touch 4g, which is working perfect, but has a broken screen. would it be easy to use the ipad 1 screen but with the ipod touch 4g hardware? Please answer to mail.erik.nilsson@gmail.com
Raymond — August 08, 2016 at 01:59 AM
Really cool blog post. I'm not sure that I am tech savvy enough to fully understand every step you describe, but I love the system you've set up connecting your laptop screen to an iPad piece by piece. Also, I love the fact that you provide links for all the products you use in your blog, makes it really handy for anyone trying to replicate it at home! Raymond @ CKS Global Solutions LTD