7" MIPI DSI touchscreen questions

Hi all, I’m looking for a 7" touchscreen for my VIM3 as the 5" TS050 is too small for my needs. I have a couple of questions:

  1. Many manufacturers say the interface is LVDS, others say it’s MIPI, but I’ve read MIPI uses the LVDS protocol. So as long as it’s a LVDS/MIPI connector with 30 pins like VIM3 it should be OK?

  2. I see some screens need different voltage, some need 9V, some 5V, some 8.6V… Which voltage can VIM3 provide through MIPI?

I was looking for a screen like this, I don’t know if someone could tell me if that’s a wrong choice or if it could work (they told me they provide the driver for Linux).

Thanks in advance

LVDS is like the transmission method and MIPI-DSI is like the Protocol

VIM3 provides 5V to the LCD panel…

your gonna need to get the drivers for the display based on what the manufacturer gives in the specification…, search online for the driver used and see if there are any linux drivers for it… (sometimes they might give you the source code and make you to compile it for the system by yourself…)

Recommendations for buying a display…

  • resolution must be equal to or less than 1980x1200 (max bandwidth of mipi-dsi 4x lanes)

  • compatible with device and driver availability

  • compatible with hardware (must be using 30 pin FPC cable (Single Sided!), and must not operate at a voltage higher than 5v

seems like a good choice…
but the backlight is using about 9.6v…

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Most of the MIPI touch screens are designed keeping RPi in mind… I think they are incompatible with all the khadas boards due to mismatch in pinout

as for LVDS panels there are driver boards that will convert LVDS to HDMI and can have touch through USB

something like this

Yes that’s why I was asking about VIM3 MIPI voltage, I’m afraid the screen will draw too much or have a voltage mismatch.

@Archangel1235 yes the problem is I can’t use HDMI as I need all the cables to go inside the box, like an integrated screen rather than an external display.

I would suggest go with a normal MIPI display and make a breakout board that will make the display compatible with VIM3

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@Archangel1235 I believe there a person who used a custom mipi display with the VIM3 a while ago, iirc

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I’m gonna search on forum to see if I can find him/her, and hopefuly some Khadas staff can answer the MIPI voltage question :smiley:

Something like the “daughterboard” of the TS050 right? But I think the only thing that board does is splitting the big flat cable (Screen + Touch) into separate Screen and separate Touch MIPI cables

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I think we discussed that one before hand…
It has special electronics to handle things like the backlighting, power distribution…

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If I were you, I would listen to the opinion of Archangel1235 :wink:

I probabily will, I can design a PCB to adapt it. The problem is I don’t know what exactly have to adapt. If it’s only doing 50/40 pin to 30 pin it will be easy, but if it’s some backlighting, power distribution and custom ICs in like @Electr1 says the khadas daughterboard does I don’t havee any kowledge of how those screens work :confused:

I agree with you, he disorientated you

I too highly don’t suggest going into designing a PCB,
If it was something like an Arduino or a Microcontroller, you could mess around with it, if you screwed something up a little, use some bodge wire…

but here, your working with Critical signal traces and stuff, if its broken, it is broken
and you need to go back to the drawing board, trust me I am sure Khadas themselves went through multiple revisions before, they got the final clean product…

Managing all those PCB traces around critical components is tough

So, try your luck with one that has the control circuitry built in…
as @Archangel1235 said, go with a HDMI one if you can, because you have two little things I might have missed telling…

In linux:

  • The Mipi panel won’t work in mainline, unless you write the MIPI driver for Mainline linux itself…

  • In BSP linux (Legacy 4.9) you are stuck with the native orientation… which means no screen rotate, unless that doesn’t matter to you… (this is the reason why the TS050 is stuck in portrait mode in Linux for now…

Bonus: I have seen these HDMI to FPC cable connectors, they convert the HDMI plug to FPC for easy routing, you can get it all kinds of configurations
might be useful…

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So many words spoken, and so few words that could help

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I don’t mind not using mainline, can use 4.9 as it’s the only one for EEMC anyway. I can draw the elements rotated 90º if that’s the only option (to trick the portrait mode). The only thing I can’t use is HDMI as I don’t want a cable going outside and inside the box again (the screen will be embedded in the box, not external).

I’m not so worried about the PCB traces as I made various PCBs already, but more about how everything works. If only Khadas could make a 7" screen for those who need a bigger one… :laughing:

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not required… just do the command sudo emmc-install, from the SD card running Mainline linux, and you will have Mainline linux in the eMMC :slight_smile:

Are you planning to make a portable device ? :smile:

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Yes that’s the idea! I’m prototyping it now but I just didn’t know that using a bigger screen would be so much trouble hahaha

All the best mate :smiley:
I would give some pointers from my device, but I am sure, you can do better…

I’m gonna spend some money and try the 7inch screen and designing an adapter for it, many of those LCDs have already integrated IC that manage almost everything so gonna try some luck adapting the pins (if needed) and using the driver they provide for Linux. If I succeed I’m gonna post it and probably the designed board schematics aswell, but I think I’m gonna be here asking for more doubts in the process :laughing:

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Well, I wish my luck, and the best of the assistance I can offer to you :slight_smile:
Farewell on your project !

also, one last thing…If you find a panel using the Novatek NT35596 Driver IC, here is the documentation of it…
you won’t even require a driver… because it is what runs the TS050 :wink:
(only minimal tinkering to the Display timings might be necessary, if things like the resolution changes)

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Hi, please clarify why you were expelled from school in the US? :laughing: