ModulinoDistance: add available() API

available() returns true is the distance is retrieved and is valid; get() returns now the last value read.

Author: facchinm

src/Modulino.h

@@ -412,26 +412,29 @@ class ModulinoDistance : public Module {
   operator bool() {
     return (tof_sensor != nullptr);
   }
-  float get() {
+  bool available() {
     if (tof_sensor == nullptr) {
-      return NAN;
+      return false;
     }
+    float ret = internal;
     uint8_t NewDataReady = 0;
     tof_sensor->VL53L4CD_CheckForDataReady(&NewDataReady);
     if (NewDataReady) {
       tof_sensor->VL53L4CD_ClearInterrupt();
       tof_sensor->VL53L4CD_GetResult(&results);
     }
     if (results.range_status == 0) {
-      return results.distance_mm;
+      internal = results.distance_mm;
     } else {
-      return NAN;
+      internal = NAN;
     }
+    return !isnan(internal);
   }
-  bool isValid(float distance) {
-    return !isnan(distance);
+  float get() {
+    return internal;
   }
 private:
   VL53L4CD* tof_sensor = nullptr;
   VL53L4CD_Result_t results;
+  float internal = NAN;
 };