unsigned long highStartTimes[NUM_CHANNELS + 1];

void readPins() {
	const unsigned long now = micros();
//	Serial.print("Interrupt started: ");
//	Serial.println(now);
	for(byte ch = 1; ch <= NUM_CHANNELS; ch++) {
		byte pin = channels[ch];
		boolean isHigh = digitalRead(pin) == HIGH;

		if(isHigh && highStartTimes[ch] == 0) {
			// First time seeing this pin go high.
			highStartTimes[ch] = now;
		} else if(!isHigh && highStartTimes[ch] != 0) {
			// Channel was high, now low. Record how long it was high for.
			channelVals[ch] = now - highStartTimes[ch];
			highStartTimes[ch] = 0;
		}
	}
}