I'm making a circuit te be able to shutdown my Raspberry Pi after the shutdown sequence is complete to avoid sd card corruption. The circuit looks like this:
A little explanation:
The battery input which is variable from 2,5 to 3,6V and 3V average, is controlled by the switch named KEY1. When the switch is activated, the input feeds EN and the system powers up. Because the switch output is connected to a transistor, it controls the state of the GPIO that will trigger the shutdown script once the switch goes OFF. The TX pin will feed those 3V to the EN pin keeping the Raspberry Pi on while the shutdown sequence is going and the switch has already switched OFF.
As you can see, the circuit already has some protection resistors, but my concern is: could the battery input (VIN) damage the TX GPIO pin when the switch is ON by feeding voltage into the GPIO PIN directly?