Diff: inc/dust_sensor.h

Revision:

0:7bfeb237e600

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/inc/dust_sensor.h	Fri Mar 08 11:34:56 2019 +0000
@@ -0,0 +1,64 @@
+#ifndef _DUST_SENSOR_H
+#define _DUST_SENSOR_H
+
+#include "mbed.h"
+
+class DustSensor : public NonCopyable<DustSensor> {
+public:
+    DustSensor(PinName pin) : _input(pin), _cb(NULL), _busy(false) {
+
+    }
+
+    bool measure(Callback<void(int, float, float)> cb) {
+        if (_busy) {
+            return false;
+        }
+
+        _cb = cb;
+
+        _busy = true;
+
+        m.attach(callback(this, &DustSensor::calculate), 30.0f);
+        t.reset(); // reset mesurement every 30 seconds
+        _input.fall(callback(this, &DustSensor::start)); // start measuring when signal is low
+        _input.rise(callback(this, &DustSensor::stop));  // stop measuring when signal is high
+
+        return true;
+    }
+
+    bool is_busy() {
+        return _busy;
+    }
+
+private:
+    // Start Timer
+    void start(void) {
+        t.start();
+    }
+
+    // Stop Timer
+    void stop(void) {
+        t.stop();
+    }
+
+    // calculate sensor value
+    void calculate() {
+        // run measurements
+        int lpo = t.read_us();
+        float ratio = t.read_us() / (30000 * 10.0);
+        float concentration = 1.1 * pow(ratio,3) -3.8 * pow(ratio, 2) + 520 * ratio + 0.62;
+        _cb(lpo, ratio, concentration);
+
+        _busy = false;
+    }
+
+    InterruptIn _input;
+    Callback<void(int, float, float)> _cb;
+
+    bool _busy;
+
+    Timer t;                    // measure amount of time signal is low
+    Timeout m;                   // every 30 seconds calculate measurement
+};
+
+#endif // _DUST_SENSOR_H