You're powering the display with 12V? Isn't that way above its spec?
When powered by a 12V mains adapter, the NOKIA display takes two power cycles before it displays anything although the backlight comes on from the very start. That is: power on (display blank, backlight on), power off, power on (display comes on as does the backlight). Now that is odd and I am stuggling to find a way of getting it to come on at the first attempt.
Switching to a 12V battery supply, the display simply never comes on.
I am resetting the LCD via an R-C pair rather than by software
:I have read something about "bias values" but not a clue how to amend these in the PCD8544 code which is set at its default.
I have read elsewhere that some of these displays are very old
I am going to replace the LCD with another one - I have read elsewhere that some of these displays are very old, that they may still be selling surplus from 90s and that they use conductive grease for wiring inside, which tends to dry up with time and cause issues. (Although what I am experiencing isn't really answered by that idea!).