mohammadfa91
Posts: 2
Joined: Mon Jan 16, 2017 3:39 pm

Raspberry Pi 3 Smartphone LCD

Mon Jan 16, 2017 4:08 pm

Recently I was trying to connect RPI3 to a smartphone LCD which supporting MIPI DSI interface. I choose Huawei Y320 LCD (800x480) because of its documents availability and of course the price and supports 2 Lane DSI just like RPI, This is the related LCD connector schematics:
Image
Image

refrences:

https://drive.google.com/open?id=0B34SK ... 0JXRWtfbEU Y320 SCH1
https://drive.google.com/open?id=0B34SK ... kwxTTZWSEE Y320 SHC2
And I have designed PCB like images blow:
Image
Image

ref:
https://drive.google.com/open?id=0B34SK ... XlRbW9VSjA
As you see connectors are exactly designed same as official schematics.
Backlight voltage is 28V.
VCI: 3.3V
IOVCC: 1.8V
All other connections from Lcd pin to RPI board triple checked !!! quite sure no interconnection and disconnection. In config.txt file I have added these lines:

Code: Select all

ignore_lcd=0
display_default_lcd=1
I tried this for windows 10 iot core, Anroid Thing, Raspbian jessie. But nothing happened! just a white backlight. I even tried this code but nothing changed.

Code: Select all

lcd_rotate=2 
and resolution setting. I have checked all DSI pins with oscilloscope but no waveform.By replacing same LCD didn't work too. HDMI connection is working perfectly but DSI ...

If DSI protocol needs to have a specific driver, how can I add and compile in source codes?
This link is the source of Linux kernel for RPI:
https://github.com/raspberrypi/linux

And this one is the source of Y320:
http://emui.huawei.com/en/plugin/hwdown ... modelId=99

Maybe we could port Y320 touchscreen by instruction described below:
https://forum.xda-developers.com/showth ... ?t=1330162

What about DSI :?:
Is this where DSI lib defined?
\drivers\gpu\drm

klricks
Posts: 6495
Joined: Sat Jan 12, 2013 3:01 am
Location: Grants Pass, OR, USA
Contact: Website

Re: Raspberry Pi 3 Smartphone LCD

Mon Jan 16, 2017 6:09 pm

At present the DSI port is closed source and only the official RPF screen can be used in the DISPLAY (DSI) port.
Unless specified otherwise my response is based on the latest and fully updated Raspbian Buster w/ Desktop OS.

mohammadfa91
Posts: 2
Joined: Mon Jan 16, 2017 3:39 pm

Re: Raspberry Pi 3 Smartphone LCD

Mon Jan 16, 2017 6:34 pm

klricks wrote:At present the DSI port is closed source and only the official RPF screen can be used in the DISPLAY (DSI) port.
Right, that's why I insist on reverse engineering of kernel source codes.
Edit: Since I remember most internal interfaces such as touch screens, LCD ,... Never been open source. So we can't expect DSI to be open source someday.
Last edited by mohammadfa91 on Tue Jan 17, 2017 2:33 am, edited 2 times in total.

asavah
Posts: 350
Joined: Thu Aug 14, 2014 12:49 am

Re: Raspberry Pi 3 Smartphone LCD

Mon Jan 16, 2017 6:48 pm

mohammadfa91 wrote:
klricks wrote:At present the DSI port is closed source and only the official RPF screen can be used in the DISPLAY (DSI) port.
Right, that's why I insist on reverse engineering of kernel source codes.
Thanks,
Kernel sources are fully open and publicly available.
You need to reverse VC4 firmware which is very different beast and AFAIK there not too many people on this planet who know how it works.
Good luck with that.

There is an open version of rpi firmware https://github.com/christinaa/rpi-open-firmware but it seems that it's far from completion.

dimitry_ishenko
Posts: 1
Joined: Fri Aug 25, 2017 8:47 pm

Re: Raspberry Pi 3 Smartphone LCD

Fri Aug 25, 2017 9:42 pm

mohammadfa91 wrote:
Mon Jan 16, 2017 4:08 pm
If DSI protocol needs to have a specific driver, how can I add and compile in source codes?
Some (most?) MIPI displays require certain initialization sequences, which are usually stored in VBT (Video BIOS Table):
https://www.kernel.org/doc/html/latest/ ... -table-vbt

It seems to be Intel-specific thing and I am not sure how other vendors do it.

VBT is stored in the BIOS (UEFI) and is extracted by the Intel gfx driver during boot. Block 53 of the VBT contains various sequences to control the display (on/off, backlight on/off, etc): http://elixir.free-electrons.com/linux/ ... bios.h#L50

I do not have an RPi and don't know much about it or how it initializes the "supported" screen.

I did however, run into a similar problem with an x86 based board. Was trying to use a screen from a another model. I ended up extracting the VBT from the other model and added a small patch to the kernel to load it like firmware and got it working.

I am now trying to do something similar with LattePanda, but haven't quite figured out what all the pins on the MIPI DSI connector mean.

Anyway, hope any of this data is of use to you.

TeoLan
Posts: 3
Joined: Sun Jun 02, 2019 4:06 pm

Re: Raspberry Pi 3 Smartphone LCD

Sun Jun 02, 2019 4:26 pm

mohammadfa91 wrote:
Mon Jan 16, 2017 6:34 pm
klricks wrote:At present the DSI port is closed source and only the official RPF screen can be used in the DISPLAY (DSI) port.
Right, that's why I insist on reverse engineering of kernel source codes.
Edit: Since I remember most internal interfaces such as touch screens, LCD ,... Never been open source. So we can't expect DSI to be open source someday.
Hello,

CM3+ user have successfully got signal from a custom LCD panel using DSI output with the latest KMS drivers update.
viewtopic.php?f=98&t=240389
Didn't you try them by chance?

Regards.

Return to “Advanced users”