I am trying to bypass the pushbutton of an external device (an LTE Hotspot) and switch it on using a Raspberry Pi. The pushbutton pulls down 1.8V for 2 seconds and then the external device powers on. I'd like to do this using an RPi but since it runs at 3.3V I am hesitant to tie it directly to one of the GPIOs as I don't know if the device is 3v3 tolerant. Ideally, I could have used a logic shifter but the external device does not expose the Vdd.
Is there a way to perform a unidirectional level shifting with minimum components? Any ideas are welcomed.