Arduino External Interrupt Not Fast Enough - arduino

Question

I've been trying to measure the time that the line is high on the Arduino. It goes high, then stays high for a couple of milliseconds. Then it gets pulled low for 1us and then floats back to high. My code doesn't seem to recognise the line getting pulled low. Is 1us too fast for the interrupt? How can I slow it down?
Thank you
EDIT
My thoughts are to use an RC filter in conjunction with a diode to slow the rise time enough for the Arduino to recognise the change, but only when the change occurs from the receiving line. Is this viable? Or can I use a pulse extender chip with a diode in the same way?
#define ESC 2 //the digital pin the esc signal line is attached to
int throttlePos = 0;
volatile unsigned long timer_start;
volatile int last_interrupt_time;
volatile int pulse_time;
void setup() {
// put your setup code here, to run once:
pinMode(ESC, OUTPUT); //originally set the ESC's line to output to keep line high ready for throttle armature
digitalWrite(ESC, HIGH); //keep the pulse high due to inverted throttle pulse
Serial.begin(115200); //opens the serial port for use when testing
timer_start = 0;
attachInterrupt(digitalPinToInterrupt(ESC), calcSignal, CHANGE);
for(throttlePos = 0; throttlePos <= 1000; throttlePos += 1) //these for loops arm the ESC by emulating an inverted PWM pulse, process takes two seconds
{
digitalWrite(ESC, LOW);
delayMicroseconds(1500);
digitalWrite(ESC, HIGH);
delayMicroseconds(100);
}
for(throttlePos = 1000; throttlePos <= 2000; throttlePos += 1)
{
digitalWrite(ESC, LOW);
delayMicroseconds(1000);
digitalWrite(ESC, HIGH);
delayMicroseconds(100);
}
}
void loop() {
digitalWrite(ESC, LOW);
delayMicroseconds(1200);
digitalWrite(ESC, HIGH);
delayMicroseconds(100);
delay(19);
Serial.println(pulse_time);
}
void calcSignal()
{
//record the interrupt time so that we can tell if the receiver has a signal from the transmitter
last_interrupt_time = micros();
//if the pin has gone HIGH, record the microseconds since the Arduino started up
if(digitalRead(ESC) == HIGH)
{
timer_start = micros();
}
//otherwise, the pin has gone LOW
else
{
//only worry about this if the timer has actually started
if(timer_start != 0)
{
//record the pulse time
pulse_time = ((volatile int)micros() - timer_start);
//restart the timer
timer_start = 0;
}
}
}

Answer 1

1/1us is 1MHz. Given that your Arduino executes instructions at 16MHz (at best, some instructions take longer), your interrupt handler could easily be missing things. However, the interrupt should still execute, even if the interrupt condition is cleared before the interrupt finishes.
Are you using the Arduino libraries for interrupts or configuring pin change interrupts directly at the register level?
Have you verified that the pulse into the Arduino is electrically sound? Without knowing more about your circuit, it's difficult to suggest a fix.