Third-party cheap touchscreen/LCD for the Pinephone - lost knowledge?

[mikeb]

Somewhere (not on this forum) there was a pretty detailed article that described how to replace a touch panel of the Pinephone - or perhaps the whole LCD assembly - with a third-party one from AliExpress instead of from Pine64. AliExpress alternative was much cheaper, had more shipping options and didn't have any availability problems (i.e. at the moment a Pine64's Pinephone LCD replacement - is "out of stock" for a pretty long time).

I had this article saved somewhere in my bookmarks, but now I can't find it anywhere - and extensive googling does not help yet. Two things that I remember:

• it turned out that Pine64 changed the pinout of touch to make it more "proprietary" (maybe so that everyone is forced to buy this replacement part from Pine64), two pins were switched - but I don't remember which ones
  
• this article was a couple of years old
  

If you have stumbled upon this article and have it saved somewhere, maybe in web archive (I don't know if this website is still alive), please let me know.
Alternatively, this knowledge may be re-obtained because we know it is possible and where to "dig" (i.e. check how the alternative panel's pins are routed)

EDIT: some keywords may involve "Goodix" "GT917S" "I2C" (Goodix GT917S touch panel's controller talks with a Pinephone over the internal I2C),
of course the replacement touch panel should be based on the same controller in order for it to work without any software/firmware modifications;
a similar-enough Goodix from the same "GT9xx" family - like GT911 or GT915 - may also work as a substitute

EDIT 2: there also may be some way to fix an existing touch panel, like using a gas lighter's quartz igniter - it works for some people, but may be dangerous:

Buy a two dollar lighter that uses a piece of quartz as an ignition source... Electrical discharge... Not the type with a piece of flint inside. The main difference and clue you have the right one is, the flint one has the rollers on top you run your thumb across as you press down on the button/trigger to release its gas for ignition. The lighter you want has just one button/ trigger. First vent or empty butane gas... Release valve on bottom. Then remove the quartz igniter from the lighters housing and place on you phones dead screen click/ press it a couple of times..for me three times. Dead zone/dead bar fixed.. no more ghost touches either. Fixed... 2.00 dollars... but keep igniter around in case screen goes dead again but after a couple of clicks screen permanent fix for me. For a detailed youtube video of the process, search keywords screen fix quartz iginiter.... the error is a digitizer fault, often due to your phone overheating for long periods at a time. The quartz igniter generates around 350 to 400 volts to the lcd screen and attached digitizer ..harmless to your phone and you... this electrical discharge that awakens the dead zone like magic. No costly repairs of digitizer and LCD screen

[mikeb]

"EDIT 2" advice above - did not help me: did not broke anything but no improvements either. Therefore my current strategy is to find a suitable touchscreen from another phone - with the same GT917S chip for a guaranteed software compatibility and with a screen size slightly smaller than a Pinephone's 5.99" (to avoid the installation problems). Yes, there will be some hassle with separating the malfunctioning touchscreen from a currently installed LCD - but I cannot find the whole screen assembly that has the same pair of chips (LCD+touch) as a Pinephone, so this is the best possible option

• According to this Blackview BV4900 Pro listing, a 5.7" touchscreen for this smartphone uses the same GT917S touchscreen chip and therefore should be compatible with the Pinephone. It is also rugged (Gorilla Glass 3), hopefully will be more reliable than Pinephone's crappy touch, and is dirt cheap - about $4 with free shipping
  

Guess I will try to order this BV4900 screen and replace the Pinephone's crapware one. Hopefully the pinout is either the same or it won't take much trouble to change it

[mikeb]

BV4900 touch screen panel aka digitizer - has arrived to me!

Advantages:
1) Has been created for a rugged IP68 phone and its thick glass feels super reliable
2) Should fit geometrically: horizontally - ideal, vertically - is slightly smaller, but should not be an issue
3) Dirt cheap - just $4 with shipping included, is available worldwide and all the time
4) Technically is compatible with Pinephone, because it indeed has the same Goodix GT917S chip according to the chip/cable markings:

Code:

GOODIX
GT917S
1950-T052
172M20
AP2A2S8P01
20-03-24 FSC
225-FPCV1-917S

Difficulties:
1) BV4900's touch panel flex cable is located at the bottom, while Pinephone's is located at the top - so I need to craft some extension cable, thin enough to fit into the phone, probably FPC-based
2) These touch panels have different pinouts and connectors; according to the flex cable markings that luckily tell us the pinouts:

Code:

BV4900 - 0.8mm pitch 6-pin FPC connector:
1. SCL
2. SDA
3. RST
4. INT
5. VDD
6. GND

Code:

Pinephone: 0.5mm pitch 6-pin FPC connector
1. GND
2. SDA
3. SCL
4. VDD
5. INT
6. RST

So, if I don't want to solder the directly to the flex cables, then I also need to somewhere get two FPC connectors of these different pitches and create a thin enough adapter that will function as an extension cable (from a bottom to top) and also changes the pinout. Definitely possible, but slightly time consuming
3) Carefully separate the Pinephone's touch panel from LCD without breaking it - unfortunately it turned out that a glue between touchscreen and LCD is much stronger than a glue between the LCD and its metal backplate and I ended up warping the whole thing while separating by slowly pulling a string between them   (or maybe I didn't heat it enough, the max I used was 150 C) . Now, I need to find a screen with ST7703 controller and preferably the same pinout