Geiger kit and Arduino

[xfpd]

@SemperIdem

The count variable should be qualified "volatile", and because it cannot be accessed atomically, it must be read within the loop function and copied with interrupts disabled.

I have updated the simulation (post 14) with @SemperIdem ISR advice on volatile:

volatile unsigned long count;     //variable for GM Tube events
// unsigned long count;              //variable for GM Tube events

The Arduino.cc reference to attachInterrupt(); recommends using digitalPinToInterrupt() as the first parameter

  attachInterrupt(digitalPinToInterrupt(GMtube), tube_impulse, FALLING);  //define external interrupts

And further updated (the sim, post 14) on advice @SemperIdem to disable interrupts when accessing count (which resides inside the ISR) from loop()...

    noInterrupts();                                   // disable interrupts to access count in ISR
    CPM = multiplier * count;                         // Estimation of CPM
    interrupts();                                     // enable interrupts after access to count in ISR
.
.
    noInterrupts();
    count = 0;
    interrupts();