A simple Squirrel class for handeling pulses as a type of digital input and a simple example using it. NOTE: Accuracy has NOT been tested.

pulse.js

/*******************************************************************************
 * Reads a pulse (either HIGH or LOW) on a pin. If the pulseValue is HIGH,
 * the object will start timing when the pin goes HIGH, then waits for the pin
 * to go LOW, and executes the callback (callback expects a function with one
 * parameter, the length of the pulse in microseconds).
 *
 * The accuracy of this function has not been tested, and will have some 
 * variance because of how callbacks work.  
 ******************************************************************************/
class Pulse {
    pulsePin = null;        // Pin to look for pulses on
    pulseValue = null;      // 1 for HIGH -> LOW, 0 for LOW -> HIGH
    timer = null;           // Time since start of pulse
    callback = null;        // callback function when pulse finished
    
    constructor(_pulsePin, _inputType, _pulseValue, _callback) {
        this.pulsePin = _pulsePin;
        this.pulseValue = _pulseValue;
        this.timer = 0.0;
        this.callback = _callback;
        
        this.pulsePin.configure(_inputType, pinChanged.bindenv(this));
    }
    
    function pinChanged() {
        local p = pulsePin.read();
        if (p == pulseValue) {
            this.timer = hardware.micros();
        }
        else {
            this.timer = hardware.micros() - timer;
            this.callback(timer);
        }
    }
}

function pulsed(microseconds)
{
    server.log("pulsed for " + microseconds + " microseconds");
}

pulsePin1 <- Pulse(hardware.pin1, DIGITAL_IN_PULLDOWN, 1, pulsed);
server.log("ready");