Interrupt variable exceeds volatile long's 8bit size

[jremington]

@kerrmit_the_frog

'This means that while your main code section (e.g. your loop) reads the first 8 bits of the variable, the interrupt might already change the second 8 bits.

Prevent that from happening by turning off interrupts, make a copy of the variable, and use the copy. For example:

volatile long counts = 0;
...

//in loop

noInterrupts();
long count_copy = counts; //make a copy
interrupts();

Serial.println(count_copy); //display the copy