Using Cell Phone Screens With Any HDMI Interface

Thanks to the worldwide proliferation of smartphones, tiny high-resolution displays are common and cheap. Interfacing these displays with anything besides a phone has been a problem. [twl] has a board that does just that, converting HDMI to something these displays can understand, and providing a framebuffer so these displays can be written to through small microcontrollers.

[twl] is using a rather large FPGA to handle all the conversion from HDMI to the DSI the display understands. He’s using an Xilinx Spartan-6-SLX9, one of the most hobbyist friendly devices that is able to be hand soldered. Also on the board is a little bit of SDRAM for a framebuffer, HDMI input, and a power supply for the LCD and its backlight.

On the things [twl] has in his ‘to-do’ list, porting Doom to run on a cellphone display is obviously right at the top. He also wants to test the drawing commands for the Arduino side of his board, allowing any board with the suffix ~’ino to paint graphics and text on small, cheap, high-resolution displays. That’s a capability that just doesn’t exist with products twice [twl]’s projected BOM, and we can’t wait to see what he comes up with.

You can check out the demo video of [twl]’s board displaying the output of a Raspberry Pi below. If you look very closely, you’ll notice the boot/default screen for the display adapter is the Hackaday Jolly Wrencher.

66 thoughts on “Using Cell Phone Screens With Any HDMI Interface

          1. r3: I find that very hard to believe. We know for a fact that there are 1440p smartphone displays out on the market already (in the LG G3 and Samsung Galaxy Note 4). We also know that there are existing HDMI receiver chips that can handle 2k and, possibly, even 4k (such as the Analog Semiconductors ADV7619, to say nothing of the other HDMI receivers that must exist in order for all the other, larger, 2k & 4k monitors out on the market).

            Now, it may be possible that this particular project can’t handle 1440p if the FPGA he used just can’t handle the bandwidth and/or processing power, but that wouldn’t be a universal issue in regards to all mobile screens over FHD (1080p). Is that what you were referring to?

          2. @Colecoman – – – i’m not sayin it’s technically impossible .. all i’m sayin that if i wanted to get some of dem boards from china ( they got all sorts of stuff ) ; however, I’ve asked specifically for this solution and response was … maybe in 6 months

      1. Only if the device works right…
        I have bought one of those universal LVDS coverters from ebay without it being programed (cost a 1/3 of what a programed one did) and used some firmware image I painstakingly found on the internet… for the love of whatever you consider holy, I cannot get the thing to run in native resolution, the HDMI interface wants to run in all others but not this one, the problem seems to be in the firmware image, but it’s machine code, so I can’t modify it…

    1. yes, and you will NEVER be able to use it freely because of Broadcom

      just like mipi CSI on pee, its there, but broadcom wont let you use it for anything other than their branded camera module using their binary blob

      1. In all fairness, that’s just as likely to be the fault of the MIPI as it is to be Broadcom’s fault. As far as I’m aware, the MIPI interface standards are closed industry standards that requires you to pay a toll to MIPI in order to gain access to the “secret sauce”. I wouldn’t be surprised if the lack of CSI/DSI documentation is because of contractual obligations between Broadcom and MIPI that tie Broadcom’s hands.

        There are more than enough legitimate closed source/binary blob issues, in regards to Broadcom. I don’t see a reason to tack this on them too if it’s this likely it isn’t really there fault.

        1. There is no secret sauce – just look at SoC application notes & datasheets, presentations, training documents, Android kernel driver sources… All the knowledge to implement an FPGA MIPI DSI master is out there and is not NDAed.

          Concerning Broadcom – IMHO it’s their corporate policy, they’ve never been too open about their stuff. If you look at datasheets of other SoC manufacturers, their MIPI interfaces are well documented, with open source drivers.

        1. this guy “http://dp2retina.rozsnyo.com/” is a pain to deal with .. bad communication .. not to mention he is business un-friendly … i would rather get my controller for ipad from Japan .. and is much much much cheaper.

        2. Commercial copycats? We have done the DP2RETINA interface without any documentation to the actual screen back in 2012. Wiring up a display according according to datasheet is not hacking :)

      1. When you say it’s been done. It’s not really because that’s a DisplayPort and not a hdmi port.
        I need hdmi for my mobile monitor application as it can be found on nearly every device with a video out now also hdmi you can get cheep long leads of decent quality. Preferably a 5v power feed is the best due to the explosion in power banks for iPads.
        This board is perfect. I just need someone to make one for me. I’m not sure I know what I’m doing with the code. I’d be pretty confident making the board possibly. But I’m in the dark with respects to code and software.

        Can anyone help an enthusiastic soul??

        1. google…could have even back when you asked this. there are display port to hdmi converters that go the rest of the way… or u know… buy a device with display port because it kicks ass. DP can pretend to be just about any standard you need it to be with a passive dongle.

  1. Since this includes a frame buffer, maybe this can be adapted to convert an HDMI signal so it can be fed to the camera input of a RaspberryPi, for inexpensive uncompressed HDMI to .264 realtime hardware compression. Apparently, since the camera for the RaspPi is sychronized by the processor for each frame, and regular HDMI obviously provides it’s own sync, a frame buffer would be required…

  2. It would be interesting to be able to use smart phone as HDMI display, not just the screen. What I am looking for is a devise that codes the HDMI video to .264 or similar and feds it via USB to phone that decodes the .264 and all with minimal latency.

  3. does anyone know if i can use the sonys xperia z5 premium screen with a kit/module to connect it to an hdmi for a homemade vr headset?
    and wich module/kit dou you recomment in this case?
    tnx

  4. Has anybody tried the opposite? Making a converter so that any screen can be used with a phone motherboard (so people with broken $200 OLEDs can swap it out for an LCD instead?).

  5. Hi;

    Just found your web page whilst searching for info on whether I could use an HTC Desire HD screen as a display for a Raspberry Pi. Do you know if this is possible?

  6. Many tablet android phone users are still confused. Touchscreen broken tablet is different from the damage to the LCD. Both parts are different, LCD and touchscreen is a separate item, the touchscreen damage only happens on the screen (thin) at the top / outside only, not the LCD part in it. You can visit the insurance displayverzekering.nl display

  7. If I wanted to use a composite decoder IC, and drive a cheap smartphone screen to just display composite video (yellow RCA jack style) would that be easier than this, or like, impossible?

  8. This is a great idea! Ideal for DIY projector enthusiasts who use 7-10″ LCD panels from tablets. It makes the final project way smaller!. Looking forward for further development of this project. Keep up the good work!

  9. I’m new here. I have access to a bunch amoled screens from the galaxy tab am-t800 series, and I can’t find a controller board for the 10.5″ screen much less anything that Willy include the capacitive touch capability. Has anyone explored Samsung amoled tech here before?

  10. Firstly i wish to congratulate you for developing all these hacks. I have a question. is it possible to develop a board that reverts the signal from “HDMI –>DSI ” to “DSI –> hdmi”? I make this question because i have a s7 edge, that, as you know, has no support for MHL neither displayport and i would like to connect it thru its lcd fpc connector.

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