Assignment by bitwise OR
From Microduino Wiki
=|(Compound bitwise or)
Description
Compound bitwise is represented by "|=", which is used to set one bit of a variable or a constant as 0 or 1.
Syntax
x |= y; // equal to x = x | y;
Parameters
x: char, int, or long int variable
y: char, int, or long int constant
Example
Look at the usage of bitwise or(|) firstly.
0 0 1 1 operand 1 0 1 0 1 operand 2 ---------- 0 1 1 1 (operand 1 & operand 2) - Returned value