Pluging and unpluging from SKR and TFT35

In this section is mentioned not to plug or unplug anything on board while in power.

does it also include TFT35 V3 E3 screen? I put USB into screen before pluging board to power and the screen stayed black. When I dont plug usb into screen, it works normal with logo and everything so I wonder, maybe I should plug it into screen AFTER it is in electricity but wonder if any damage can occur. The same I wonder regarding sd card (did not try yet)

It’s bad practice, but you would be unlikely to do any damage.

I’ve been doing a bit of testing any have plugged in and unplugged the serial line for the TFT35, but not the grey Marlin mode plugs. Those should also be OK, but I do worry a bit about the SD card reader which is attached to those

The TFT USB port isn’t used to power the TFT. It’s intended as a host port, for a USB thumb drive, not as a peripheral port. While I wouldn’t be surprised if it did power up the 5V bus, I would definitely not expect it, and would not use it that way.


Did you have any problem reading USB via TFT35?

No. It is really the inductive loads of the steppers that this is warning about. If you disconnect them, the current will find a way and that can shock the board.

The other danger is just shorting two exposed pins, because the board isn’t completely protected. Moving wires around could accidentally short something.

The USB behavior you described isn’t normal though. So I would be worried the screen is protecting itself. Not sure what to do with that information. It should boot fine with a usb in it.

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How could moving wires short something when they are isolated?

I had no idea about disconnecting steppers, thanks for info.
The USB screen behavior is still happening when USB is in it before pluging it into power. I dont know why it is happening.

If you are careful, it won’t happen. But if you are moving things around with your fingers, or you use pliers, or something comes loose and a bare connector is exposed, or if you plug something in wrong (like an endstop into the + and - parts). It is just good practice to not hot swap most of these things. They aren’t as well protected as a laptop, which has a well designed case and circuit protections on all the ports.

If you want to be really pedantic, there is a significant static shock risk from just touching the board when it isn’t in a case. So the best advice is to be more careful than you would for normal consumer devices.

We have seen people try to measure things with multimeters and accidentally short something. And the endstop + connector is always a danger. But not much of that has happened recently.


Thanks for an answer. That actually makes a lot of sense. I am usually touching board after I press emergency stop on display and have to reset board. But it is also possible to do it by unplugging and plugging from the power, so I guess I will rather do it that way.
I never hot swapped anything, but You are right, by moving cables around, I could accidentally touch some pin and short something.