3.5" LCD won't work with Fan Shim

Are we sure its not booting up? Maybe the display is just garbled? I’m not sure that helps but I’m just cuprous as to whether it actually fails to boot or not. You could try hooking up an HDMI display.

It does fail to boot. I left it go for an hour on mine and could not SSH into it. Something is different between the Pi 3b and Pi 4. My Pi 3b has been running the fan shim and 3.5 display together for about a month now with no issues. The same parts I gave up trying to get to work on my Pi 4.

Ok, it is in fact not booting up. I have no idea why though?

@Silarous I am going to need your help to get the current state of those pins on the PI3

What I am trying to achieve with this is to know the difference between the Pi4 and Pi3 as far as GPIO configuration and current state.

Please install only the Fan Shim on your PI3 and once is fully online open a terminal and run the following commands:

  1. sudo raspi-gpio get 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40" > fan_full_gpio.log

  2. watch -d "sudo raspi-gpio get 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40"

The previous command will highlight if there is any change on any field. for instance if one of the levels change. Most likely you will see changes in some levels. Please let it run for 2-3 min and Please write down the gpios that change.

  1. Please repeat steps 1 and 2 without the fan and Only with the LCD and rename the output file to lcd_full_gpio.log instead of fan_full_gpio.log

  2. Please repeat steps 1 and 2 with the Fan and LCD, and rename the output file to lcdfan_full_gpio.log instead of fan_full_gpio.log

I am doing the same with the PI 4 and I will compare my finding and try to findout if something can be done at the software level.

Cheers

Not a problem. I will try and get that done later tonight!

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With Fan Shim, no Display - GPIO 34

With Display, no Fan Shim - GPIO 34

Both situations only have pin 34 that highlights.

could you share your fan_full_gpio.log and lcdfan_full_gpio.log

Sure if you tell me how to find and display a log.

  1. fan only
    sudo raspi-gpio get 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40" > fan_full_gpio.log

  2. lcd only
    sudo raspi-gpio get 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40" > lcd_full_gpio.log

  3. fan and lcd
    sudo raspi-gpio get 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40" > lcdfan_full_gpio.log

when you run these commands you will endup with 3 files : fan_full_gpio.log, lcd_full_gpio.log, lcdfan_full_gpio.log.

They will be in whatever directory you run this commamd

How do you display the log? I know nothing when it comes to Linux. I can follow a guide though. Have to be detailed for me unfortunately.

you can just run the following commands:

  1. cat fan_full_gpio.log
  2. cat lcd_full_gpio.log
  3. cat lcdfan_full_gpio.log

cat fan_full_gpio.log comes back “Too many arguments”

you can replace cat with the following commans: