Add ESP::deepSleep(us)

fixes: https://github.com/espressif/arduino-esp32/issues/51

cores/esp32/Esp.cpp

@@ -20,6 +20,7 @@
 #include "Arduino.h"
 #include "Esp.h"
 #include "rom/spi_flash.h"
+#include "esp_deep_sleep.h"
 #include <memory>
 
 //#define DEBUG_SERIAL Serial
@@ -80,6 +81,11 @@ unsigned long long operator"" _GB(unsigned long long x)
 
 EspClass ESP;
 
+void EspClass::deepSleep(uint32_t time_us)
+{
+    esp_deep_sleep(time_us);
+}
+
 uint32_t EspClass::getCycleCount()
 {
     uint32_t ccount;

cores/esp32/Esp.h

@@ -60,6 +60,7 @@ public:
 
     const char * getSdkVersion();
 
+    void deepSleep(uint32_t time_us);
 
     uint8_t getCpuFreqMHz();