HardwareTimer: Fix frequency computation when there is no more signal

When HardwareTimer is used in input capture mode,
we need to handle the case where timer counter rollover.
Let's set values to 0 in both examples:
* InputCapture
* Frequency_Dutycycle_measurement

FIX 789

Author: ABOSTM

examples/Peripherals/HardwareTimer/Frequency_Dutycycle_measurement/Frequency_Dutycycle_measurement.ino

@@ -38,6 +38,13 @@ void TIMINPUT_Capture_Rising_IT_callback(HardwareTimer*)
   LastPeriodCapture = CurrentCapture;
 }
 
+/* In case of timer rollover, frequency is to low to be measured set values to 0
+   To reduce minimum frequency, it is possible to increase prescaler. But this is at a cost of precision. */
+void Rollover_IT_callback(HardwareTimer*)
+{
+  FrequencyMeasured = 0;
+  DutycycleMeasured = 0;
+}
 
 /**
     @brief  Input capture interrupt callback : Compute frequency and dutycycle of input signal
@@ -103,6 +110,7 @@ void setup()
   MyTim->setOverflow(0x10000); // Max Period value to have the largest possible time to detect rising edge and avoid timer rollover
   MyTim->attachInterrupt(channelRising, TIMINPUT_Capture_Rising_IT_callback);
   MyTim->attachInterrupt(channelFalling, TIMINPUT_Capture_Falling_IT_callback);
+  MyTim->attachInterrupt(Rollover_IT_callback);
 
   MyTim->resume();
 

examples/Peripherals/HardwareTimer/InputCapture/InputCapture.ino

@@ -27,6 +27,12 @@ void InputCapture_IT_callback(HardwareTimer*)
   LastCapture = CurrentCapture;
 }
 
+/* In case of timer rollover, frequency is to low to be measured set value to 0
+   To reduce minimum frequency, it is possible to increase prescaler. But this is at a cost of precision. */
+void Rollover_IT_callback(HardwareTimer*)
+{
+  FrequencyMeasured = 0;
+}
 
 void setup()
 {
@@ -53,6 +59,7 @@ void setup()
   MyTim->setPrescaleFactor(PrescalerFactor);
   MyTim->setOverflow(0x10000); // Max Period value to have the largest possible time to detect rising edge and avoid timer rollover
   MyTim->attachInterrupt(channel, InputCapture_IT_callback);
+  MyTim->attachInterrupt(Rollover_IT_callback);
   MyTim->resume();
 
   // Compute this scale factor only once