Doesn't work in an ISR

I want a LED to turn on for 10ms every time when I call this function:

```
volatile void ledA1Pulse(int ms)
{ ledA1.turnON();
 ledA1.turnOFF(ms);
}
```

```
volatile ezLED ledA1(testPinA1);

loop()
{ ledA1.loop();
}
```

It works fine without using a ISR.
But not if the function is in an ISR.