Power & Source of Big Ideas

HiDPI/Retina Display direct eDP connection

Moderators: chensy, FATechsupport

Hi,

I run my NanpPC T4 with an old iPad Retina Display via an HDMI->eDPaAdapter.
I want to omit the interface and use the eDP port, as the adapter runs very hot.

Has anyone managed to get the eDP interface working for a 3rd party display (i.e. not the 7" supplied by FriendyArm?)
Which cables, adapters and backlight LED power supply did you use?
Was a new Kernel with the proper timings necessary?

cheers

pit
0xpit wrote:
Hi,
Has anyone managed to get the eDP interface working for a 3rd party display (i.e. not the 7" supplied by FriendyArm?)
Which cables, adapters and backlight LED power supply did you use?
Was a new Kernel with the proper timings necessary?


I am about to embark on creating a custom display for the Nano PC T3 Plus so looking at the same idea. Yes, you will most likely need to modify the kernel to work with the timing of the new display. The fun part is in getting the FriendlyArm open source 1-wire to do the work of auto-detection. I am just starting to look at this in the kernel drivers and at the source for the 1-wire.

If you copy the schematic for the eDP LCD from FA, you should be able to keep most of it and remove what you don't need. For my display I don't need any other voltages other than 3.3V so it becomes much simpler.
Well, it should also work with a DTS overlay, as per http://wiki.t-firefly.com/en/Firefly-RK ... r_lcd.html, so it might be possible to use the stock kernel.

Also, I do not understand what you mean with 1-wire? There is no 1-wire on either the eDP connector nor on the iPad LCD Modules. The regular AUX Channel wire pair on eDP can support detection of the display and the protocol used is well documented.

I'm very much interested in getting a suitable cable, theoretically it should be possible to operate those displays with the right cable and configuration (or kernel) and a matching backlight LED driver.
You are correct, there is no 1-wire on the eDP display and the schematic for the eDP display HD702V shows that they seem to be using I2C to talk to the STM8 that handles the LED dimming and backlight control. They must be using the I2C to detect what display is attached and adjust the kernel driver. I'll know more once I look through the kernel source.

Are you able to design your own PCB? The MIC2287CYD5-TR is a very good backlight driver capable of 30V at 500mA. Do you know what the voltage and current is for your iPAD LCD?

If you can design a PCB, you can use most of the schematic for the eDP display less all of the voltage supplies. Substitute the LED driver for the one above. The STM8 code should be open source as FA say that the 1-wire is open. I still can't find it so have emailed tech support to find out where to get this.

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