Timer Interrupts on Due

Hardware Arduino Due
119

garygid:
Put the attach hall-interrupt in the setup routine, not the loop.
and, measure the milliseconds T1 before the attachment

In the loop, display the RPM.

In the interrupt, measure the milliseconds T2
do not enable or disable the interrupt, just leave it going.
If T2 > T1 then Calculate RPM = 60000 / (T2 - T1)
then, set T1 = T2
to wait for the next interrupt

Thank you very much, your help is much appreciated.
Can be "good" this sketch example?

void setup() {
T1 = micros();
attachInterrupt(hall_pin, duration, FALLING);
}

void loop() {
RPM = 60e6 / (T2 - T1);
code here for LCD ; // display RPM on LCD
T1 = T2;
}

void duration() {
T2 = micros();
}