electronic switch to control battery from Espruino GPIO

Could it perhaps be a timing issue, as displays often need a few msec
after being powered on before they're ready?

checked that and upped the waiting times, had no success

You've also got to be careful that you don't power them up via their
IO lines first (eg, if you init SPI beforehand)

thanks for the tip, changed the code

Shouldn't a coin cell that will never go above 3.3v be connected to
the 3.3v rail directly

the coin cell shall power the Espruino Pico and the display as well, i am not sure about this 3.3v rail, what do you mean?

...I'm sure you have looked at GPS powered by Espruino pin(s).

thx for the link, i am not sure that is the problem here, as one pin should be more than enough
but that kept me thinking, the display needs 8 pins for proper operation (SPI Clock and MOSI, and 6 more pins for e.g. chipselect)

maybe the lot of pins draw too much current so the direct connection to VBAT is needed? is there enough voltage?

ok i used a multimeter - was my first time btw, it seems more of a problem with voltage, the whole circuit is around 2,3v, but the typical operation voltage for the display goes from min. 2,4v to 3,3v