ILI9486 blank screen, no errors

[craigerl]

Raspberry Pi 3.5inch RPi LCD (B) Waveshare

(.venv) pi@digipi:~/.venv/Python_ILI9486 $ sudo ../bin/python image.py
Initialized display with landscape mode = True and dimensions (480, 320)
Loading image...
Drawing image
Drawing partial image
Turning on inverted mode
Turning off inverted mode

..

screen is blank the entire time with backlight on. dtoverlay is not loaded.

[SirLefti]

Hi Craig, sorry to hear that.

It is not mentioned in the README.md, but is SPI enabled on your device? It is not enabled by default, but I would expect a FileNotFoundError anyways if it was not enabled.

Can you provide additional information?

• which raspberry board are you using?
• which OS version is installed?
• is it a clean OS or has it been used for other things previously?
• is the display connected directly or do you use some sort of extensions?

I just cloned it onto my RPi 2B using the latest Raspberry OS based on Debian 12 Bookworm and it worked just fine.

[craigerl]

Hi SirLefti, it looks like it's isolated to Pi5. it works on a PiZero2w. Probably spidev/gpio related, i'll closer at this.

Using bookworm, original kernel (no errata).
direct connection on gpio header

Even on the PiZero2W, the "image.py" example displays an image only for two seconds, then screen blanks. I'm trying to write an app that will display a png, that's it. Not quite there. thanks!

https://www.amazon.com/dp/B07V9WW96D

#!/usr/bin/python

from PIL import Image
import RPi.GPIO as GPIO
from spidev import SpiDev
import time
import ILI9486 as LCD
import config

spi: SpiDev = None

if __name__ == '__main__':
    try:
        GPIO.setmode(GPIO.BCM)
        spi = SpiDev(config.SPI_BUS, config.SPI_DEVICE)
        spi.mode = 0b10  # [CPOL|CPHA] -> polarity 1, phase 0
        # default value
        # spi.lsbfirst = False  # set to MSB_FIRST / most significant bit first
        spi.max_speed_hz = 64000000
        lcd = LCD.ILI9486(dc=config.DC_PIN, rst=config.RST_PIN, spi=spi).begin()
        print(f'Initialized display with landscape mode = {lcd.is_landscape()} and dimensions {lcd.dimensions()}')
        print('Loading image...')
        image = Image.open('sample.png')
        width, height = image.size
        partial = image.resize((width // 2, height // 2))

        print('Drawing image')
        lcd.display(image)
        time.sleep(10)

-craig

[SirLefti]

Something comes to my mind regarding this. Pi 5 and Zero 2 are using ARMv8 64-bit SOCs, while my old 2B is ARMv7 32-bit. I assume that you have the 64-bit version of Raspberry OS installed, which might have some differences to the 32-bit version.

But I remember something else that might be relevant. I switched here in my piboy project from RPi.GPIO to rpi-lgpio, which was the initial reason writing this driver, when I rewrote the setup guide for the latest Raspberry OS based on Debian Bookworm, because the old lib had issues with edge detection. The new lib apparaently uses a different approach controling the GPIO pins. I do not understand the details, but maybe the issues have something in common.

What you can try:

• uninstall the RPi.GPIO lib
• install the rpi-lgpio lib
• run the script again

The new lib is a drop-in replacement, because its module has the same name as the old one. Thus it is required to remove the old lib to avoid conflicts.

However I have to admit that my example script also worked with the old lib for me. But as already mentioned, old SOC, 32-bit OS.

[craigerl]

yah, spi is enabled. it's a pi5 thing, in conjunction with bookworm spi and gpio were generally destroyed in favor of gpiod, possibly gpiozero. the former requires a chip id, the latter uses an entire cpu core just to monitor a button. In any event, it's easy to reproduce on a pi5 and only a pi5 with bookworm.

[SirLefti]

Okay, so you would have to rewrite it with gpiod or gpiozero to make it work,
Have you tested the mentioned rpi-lgpio as well?

[SirLefti]

I am closing this issue, because it should be fixed with the change to rpi-lgpio. If there is still any issue, hit me up again.