Add instantly option to deepSleep

cores/esp8266/Esp.cpp

@@ -114,6 +114,13 @@ void EspClass::deepSleep(uint64_t time_us, WakeMode mode)
     esp_yield();
 }
 
+void EspClass::deepSleepInstant(uint64_t time_us, WakeMode mode)
+{
+    system_deep_sleep_set_option(static_cast<int>(mode));
+    system_deep_sleep_instant(time_us);
+    esp_yield();
+}
+
 //this calculation was taken verbatim from the SDK api reference for SDK 2.1.0.
 //Note: system_rtc_clock_cali_proc() returns a uint32_t, even though system_deep_sleep() takes a uint64_t.
 uint64_t EspClass::deepSleepMax()

cores/esp8266/Esp.h

@@ -93,6 +93,7 @@ class EspClass {
         void wdtFeed();
 
         void deepSleep(uint64_t time_us, RFMode mode = RF_DEFAULT);
+        void deepSleepInstant(uint64_t time_us, RFMode mode = RF_DEFAULT);
         uint64_t deepSleepMax();
 
         bool rtcUserMemoryRead(uint32_t offset, uint32_t *data, size_t size);

doc/libraries.rst

@@ -73,6 +73,8 @@ Some ESP-specific APIs related to deep sleep, RTC and flash memories are availab
 
 ``ESP.deepSleep(microseconds, mode)`` will put the chip into deep sleep. ``mode`` is one of ``WAKE_RF_DEFAULT``, ``WAKE_RFCAL``, ``WAKE_NO_RFCAL``, ``WAKE_RF_DISABLED``. (GPIO16 needs to be tied to RST to wake from deepSleep.) The chip can sleep for at most ``ESP.deepSleepMax()`` microseconds.
 
+``ESP.deepSleepInstant(microseconds, mode)`` works similarly to ``ESP.deepSleep`` but  sleeps instantly without waiting for WiFi to shutdown.
+
 ``ESP.rtcUserMemoryWrite(offset, &data, sizeof(data))`` and ``ESP.rtcUserMemoryRead(offset, &data, sizeof(data))`` allow data to be stored in and retrieved from the RTC user memory of the chip respectively. Total size of RTC user memory is 512 bytes, so ``offset + sizeof(data)`` shouldn't exceed 512. Data should be 4-byte aligned. The stored data can be retained between deep sleep cycles. However, the data might be lost after power cycling the chip.
 
 ``ESP.restart()`` restarts the CPU.