3.5" LCD won't work with Fan Shim

Some careful hunting down and cutting of the PCB trace for this button should suffice, and I suspect it’s even possible to re-route to another pin if you’ve got any soldering tools and wire.

You could carefully drill out that pad on the fan shim so the hole is so big it doesn’t touch the GPIO pin. Somebody in another thread stated they just cut those two last pads off of the fan shim circuit board. The fan will just run continuously. You can no longer turn it on and off my temperature.
That button also connects to the “wake” pin. Thats the pin I’m using to turn my Pi on and off. GPIO 3. Phil can confirm it, but the other pin is I “think” the pin the python code poles to see if its pressed or not.

If look at the fan shim circuit board, the round pad on the end opposite the one mounting hole is GPIO 17, physical pin 11.
If you look close you’ll see a circuit track / trace going out the bottom of that pad and then turning towards the switch. If you take an exacto knife and carefully cut that track so there is a thin gap in it. That pad will no longer be connected to the switch.
Like you’d do to change the i2c address on a breakout board.

If that is the only track going to that pad, I would think that “should” do it.
I have a fan shim, I don’t have that display though.

Where I have the white line in this picture. If you carefully scrape the black paint off you should see a cooper track under it going down and then left. Cut that track so there is a gap in it. Do this at your own risk.

fan%20shim%20cut

I made the whole bigger (Pin 11) , which destroy the copper trace. There is not any difference, beside that push botton is gone, still not able to have the LCD working :-/.

I am lost :-O
These is what I tried:

  1. LCD only (drivers and services) without any changes on SW -> LCD works
  2. Fan (drivers and services) only without any changes on SW -> Fan works
  3. LCD with Fan without any changes on SW -> Board does not boot

I dont have a clue what is going on. Pin 11 is the only pin that is actually use by both devices (LCD and Fan). The connectivity on the fan side is gone since I made the whole bigger and there isnt any contact with the pin.

Is it maybe because the fan or is draining too much current that affect the LCD?

Any ideas what else to try?

To be honest I was doubtful it was the button doing it, but stranger things have happened. If its wired up the way I think it is, it only grounds that pin when and while pressed. If you don’t have you finger on the button that pin should just be floating an open circuit. Anything else that wants to use it should be able to use it.

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!

1 Like

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: