Cant setup a 3.5 inch lcd RPi display on raspberry pi 4

[alloncm]

Hi, Im trying to setup a 3.5 inch lcd RPi display I got from a friend.

I couldn't find a good docs about this display except for this site -
http://www.lcdwiki.com/3.5inch_RPi_Display
From what I understand this is an ILI9486 display so this driver support it.

Im probably not configuring the correct build parameters but I have tried twicking them for my understanding (it is my first hardware project so I dont have a lot of experience with RPI and those things) but everytime I get a white screen (sometimes it blinks a bit), also the terminal output seems to be fine.

The last command I tried to compile with:

cmake -DSPI_BUS_CLOCK_DIVISOR=40 -DGPIO_TFT_DATA_CONTROL=-1 -DGPIO_TFT_RESET=22 -DILI9486=ON ..

The terminal output when running as sudo:

bcm_host_get_peripheral_address: 0xfe000000, bcm_host_get_peripheral_size: 25165824, bcm_host_get_sdram_address: 0xc0000000
BCM core speed: current: 233333333hz, max turbo: 500000000hz. SPI CDIV: 40, SPI max frequency: 12500000hz
Allocated DMA channel 7
Allocated DMA channel 1
Enabling DMA channels Tx:7 and Rx:1
DMA hardware register file is at ptr: 0xb5388000, using DMA TX channel: 7 and DMA RX channel: 1
DMA hardware TX channel register file is at ptr: 0xb5388700, DMA RX channel register file is at ptr: 0xb5388100
Resetting DMA channels for use
DMA all set up
Initializing display
Creating SPI task thread
InitSPI done
DISPLAY_FLIP_ORIENTATION_IN_SOFTWARE: Swapping width/height to update display in portrait mode to minimize tearing.
Relevant source display area size with overscan cropped away: 1080x1920.
Source GPU display is 1080x1920. Output SPI display is 320x480 with a drawable area of 320x480. Applying scaling factor horiz=0.25x & vert=0.25x, xOffset: 25, yOffset: 0, scaledWidth: 270, scaledHeight: 480
Creating dispmanX resource of size 270x480 (aspect ratio=0.562500).
GPU grab rectangle is offset x=0,y=0, size w=270xh=480, aspect ratio=0.562500
All initialized, now running main loop...

The blank white screen:

Pictures of the display:

Thanks in advance :)

[alloncm]

Update:

After messing with this for this weekend too I have managed to get my RPI4 to output to this screen.
Ill describe here what I did in case someone will try it too in the future.

After further reading my screen docs and fbcp readme I have noticed that my screen sku is MPI3501 which is supported after this issue #40, I tried compiling to this with no success (I guess Im lucky? cause this screen seems to be shit).
After some more reading I reached this issue #191 and noticed that the screens connector looks similar and that he used some other screen config.
Anyway this command for the waveshare 35b worked for me!

cmake -DWAVESHARE35B_ILI9486=ON -DSPI_BUS_CLOCK_DIVISOR=24

Im using 24 in the clock divisor cause any number smaller than this will make the screen either stay white or display corrupted image.

The screen is a bit laggy so I might buy a better screen (with maybe more support for this driver).

Just to check, the corruption when trying to use clock divisor smaller than 24 is an expected behavior?