Reading from Wire inside an ISR

Using Arduino Programming Questions
5

or is this not possible?

It is generally not possible / advisable.

The issue is with re-entrancy: you have no way of knowing that before an isr is fired, if that very (wire) function is being called.

There are solutions around it but they fundamentally don't alter the picture:

  1. don't call a function from within the isr;
  2. if you have to, make sure that that function isn't called anywhere else.