Add methods to check if there's an IRQ handler (#764)

Author: LinoBarreca

Diff for: cores/arduino/HardwareTimer.cpp

@@ -701,6 +701,28 @@ void HardwareTimer::detachInterrupt(uint32_t channel)
   callbacks[channel] = NULL;
 }
 
+/**
+  * @brief  Checks if there's an interrupt callback attached on Rollover event
+  * @retval returns true if a timer rollover interrupt has already been set
+  */
+bool HardwareTimer::hasInterrupt()
+{
+  return callbacks[0] != NULL;
+}
+
+/**
+  * @brief  Checks if there's an interrupt callback attached on Capture/Compare event
+  * @param  channel: Arduino channel [1..4]
+  * @retval returns true if a channel compare match interrupt has already been set
+  */
+bool HardwareTimer::hasInterrupt(uint32_t channel)
+{
+  if ((channel == 0) || (channel > (TIMER_CHANNELS + 1))) {
+    Error_Handler();  // only channel 1..4 have an interrupt
+  }
+  return callbacks[channel] != NULL;
+}
+
 /**
   * @brief  Generate an update event to force all registers (Autoreload, prescaler, compare) to be taken into account
   * @note   Refresh() can only be called after a 1st call to resume() to be sure timer is initialised.

Diff for: cores/arduino/HardwareTimer.h

@@ -110,9 +110,11 @@ class HardwareTimer {
     //Add interrupt to period update
     void attachInterrupt(void (*handler)(HardwareTimer *)); // Attach interrupt callback which will be called upon update event (timer rollover)
     void detachInterrupt();  // remove interrupt callback which was attached to update event
+    bool hasInterrupt();  //returns true if a timer rollover interrupt has already been set
     //Add interrupt to capture/compare channel
     void attachInterrupt(uint32_t channel, void (*handler)(HardwareTimer *)); // Attach interrupt callback which will be called upon compare match event of specified channel
     void detachInterrupt(uint32_t channel);  // remove interrupt callback which was attached to compare match event of specified channel
+    bool hasInterrupt(uint32_t channel);  //returns true if an interrupt has already been set on the channel compare match
 
     void timerHandleDeinit();  // Timer deinitialization