Allow disabling the use of delay() calls.

src/IRremoteESP8266.h

@@ -174,6 +174,12 @@
 #define DECODE_AC false   // We don't need that infrastructure.
 #endif
 
+// Use millisecond 'delay()' calls where we can to avoid tripping the WDT.
+// Note: If you plan to send IR messages in the callbacks of the AsyncWebserver
+//       library, you need to set ALLOW_DELAY_CALLS to false.
+//       Ref: https://github.com/markszabo/IRremoteESP8266/issues/430
+#define ALLOW_DELAY_CALLS true
+
 /*
  * Always add to the end of the list and should never remove entries
  * or change order. Projects may save the type number for later usage

src/IRsend.cpp

@@ -117,13 +117,14 @@ void IRsend::enableIROut(uint32_t freq, uint8_t duty) {
   offTimePeriod = period - onTimePeriod;
 }
 
+#if ALLOW_DELAY_CALLS
 // An ESP8266 RTOS watch-dog timer friendly version of delayMicroseconds().
 // Args:
 //   usec: Nr. of uSeconds to delay for.
 void IRsend::_delayMicroseconds(uint32_t usec) {
-  // delayMicroseconds is only accurate to 16383us.
+  // delayMicroseconds() is only accurate to 16383us.
   // Ref: https://www.arduino.cc/en/Reference/delayMicroseconds
-  if (usec <= 16383) {
+  if (usec <= MAX_ACCURATE_USEC_DELAY) {
 #ifndef UNIT_TEST
     delayMicroseconds(usec);
 #endif
@@ -136,6 +137,22 @@ void IRsend::_delayMicroseconds(uint32_t usec) {
 #endif
   }
 }
+#else  // ALLOW_DELAY_CALLS
+// A version of delayMicroseconds() that handles large values and does NOT use
+// the watch-dog friendly delay() calls where appropriate.
+// Args:
+//   usec: Nr. of uSeconds to delay for.
+//
+// NOTE: Use this only if you know what you are doing as it may cause the WDT
+//       to reset the ESP8266.
+void IRsend::_delayMicroseconds(uint32_t usec) {
+  for (; usec > MAX_ACCURATE_USEC_DELAY; usec -= MAX_ACCURATE_USEC_DELAY)
+#ifndef UNIT_TEST
+    delayMicroseconds(MAX_ACCURATE_USEC_DELAY);
+  delayMicroseconds(static_cast<uint16_t>(usec));
+#endif  // UNIT_TEST
+}
+#endif  // ALLOW_DELAY_CALLS
 
 // Modulate the IR LED for the given period (usec) and at the duty cycle set.
 //

src/IRsend.h

@@ -25,6 +25,9 @@
 #define PERIOD_OFFSET -3
 #define DUTY_DEFAULT 50
 #define DUTY_MAX 100  // Percentage
+// delayMicroseconds() is only accurate to 16383us.
+// Ref: https://www.arduino.cc/en/Reference/delayMicroseconds
+#define MAX_ACCURATE_USEC_DELAY 16383U
 
 // Classes
 class IRsend {