implemented async PM sensor sampling

firmware/src/main.cpp

@@ -14,11 +14,16 @@ Sensor *pmSensor;
 BluetoothServer *server;
 bool makeDiscoverable = false;
 
-
+//interrupt handler for sensor being pressed
 void IRAM_ATTR startBleServerAdvertising() {
     makeDiscoverable = true;
 }
 
+//helper function to create task for PM measurement
+void startPmAsyncSampling(void * param){
+    ((PmSensor *) pmSensor)->startAsyncSampling();
+}
+
 void setup() {
     //initialize a Serial Connection
     Serial.begin(BAUD_RATE);
@@ -38,17 +43,25 @@ void setup() {
     attachInterrupt(digitalPinToInterrupt(INTERRUPT_MAKE_DISCOVERABLE_PIN),
                     startBleServerAdvertising,
                     RISING);
+
+    //start an async task for measuring PM so the sensor won't block the whole system
+    xTaskCreate(
+            startPmAsyncSampling,
+            "Async PM sampling",
+            1024,
+            nullptr,
+            1,
+            nullptr
+    );
 }
 
 void loop() {
+    //check if the button has been pressed and handle appropriately
     if (makeDiscoverable) {
         server->startAdvertising();
         makeDiscoverable = false;
     }
 
-    //setup PM sensor measurement TODO: This blocks for 120 seconds and needs to be executed asynchronously
-    //((PmSensor *) pmSensor)->startAsyncSampling();
-
     //obtain measurement from BMP280 Sensor
     sensor_data_t sample = ((BmpSensor *) bmpSensor)->sampleLowEnergy();
     server->setPressure(sample.pressure);
@@ -62,6 +75,7 @@ void loop() {
                   sample.temperature,
                   pmSample.pm10,
                   pmSample.pm25);
+
     //wait for one measurement cycle
     delay(SLEEP_TIME * 1000);
 }

firmware/src/sensors/PmSensor.cpp

@@ -21,19 +21,35 @@ PmSensor::PmSensor() {
     this->PmSensor::sensor_setup();
 }
 
-void PmSensor::startAsyncSampling() {
+[[noreturn]] void PmSensor::startAsyncSampling() {
 
-    this->enableStandbyMode();
-    PmSensor::sensorWait(SLEEP_TIME);
+    Serial.println("Started async task for PM sensor sampling.");
 
+    while (true) {
         this->wakeUp();
-    sds011.perform_work();
+
+        //attach a callback on what to do when data sampling is complete
+        sds011.on_query_data_auto_completed([this](int n) {
+            Serial.println("Sampled new PM data.");
+            int pm25;
+            int pm10;
+            if (sds011.filter_data(n, pm25_table, pm10_table, pm25, pm10) &&
+                !isnan(pm10) && !isnan(pm25)) {
+                //set the right values
+                this->latestPM10 = float(pm10) / 10;
+                this->latestPM25 = float(pm25) / 10;
+            }
+        });
 
         if (!sds011.query_data_auto_async(pm_tablesize, pm25_table, pm10_table)) {
             Serial.println("measurement capture start failed");
         }
 
         PmSensor::sensorWait(MEASURE_TIME);
+
+        this->enableStandbyMode();
+        PmSensor::sensorWait(SLEEP_TIME);
+    }
 }
 
 /**
@@ -41,6 +57,7 @@ void PmSensor::startAsyncSampling() {
  */
 void PmSensor::enableStandbyMode() {
     if (sds011.set_sleep(true)) { this->state = SensorState::ASLEEP; }
+    Serial.println("PM sensor went to sleep mode.");
 }
 
 /**
@@ -48,6 +65,7 @@ void PmSensor::enableStandbyMode() {
  */
 void PmSensor::wakeUp() {
     if (sds011.set_sleep(false)) { this->state = SensorState::AWAKE; }
+    Serial.println("PM sensor woke up.");
 }
 
 /**
@@ -64,18 +82,6 @@ void PmSensor::sensor_setup() {
     //put the sensor into standby mode initially
     this->PmSensor::enableStandbyMode();
     Serial.println("SDS011 sensor initialized to standby mode.");
-
-    //attach a callback on what to do when data sampling is complete
-    sds011.on_query_data_auto_completed([this](int n) {
-        int pm25;
-        int pm10;
-        if (sds011.filter_data(n, pm25_table, pm10_table, pm25, pm10) &&
-            !isnan(pm10) && !isnan(pm25)) {
-            //set the right values
-            this->latestPM10 = float(pm10) / 10;
-            this->latestPM25 = float(pm25) / 10;
-        }
-    });
 }
 
 /**
@@ -85,7 +91,7 @@ void PmSensor::sensor_setup() {
 void PmSensor::sensorWait(int time) {
     uint32_t deadline = millis() + time * 1000;
     while (static_cast<int32_t>(deadline - millis()) > 0) {
-        delay(1000);
+        vTaskDelay(1000 / portTICK_PERIOD_MS);
         sds011.perform_work();
     }
 }

firmware/src/sensors/PmSensor.h

@@ -17,7 +17,7 @@ public:
 
     sensor_data_t sample() override;
 
-    void startAsyncSampling();
+    [[noreturn]] void startAsyncSampling();
 
 
     void enableStandbyMode() override;