Adding deep sleep example.

The program is a simple loop: Read VDD, sleep for 5 second.

examples/deepsleep/Makefile

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+ROOT = ../..
+
+#FLASH_SIZE=512
+#OTA=0
+
+include $(ROOT)/Makefile.common

examples/deepsleep/readme.md

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+To read VDD
+-------------------
+
+The 107th byte in esp_init_data_default.bin (0~127byte) is named as "vdd33_const" , when TOUT pin is suspended vdd33_const must be set as 0xFF, that is 255.
+
+Should change byte 107th of esp_init_data_default.bin to run this program.
+
+With vi:
+:%!xxd
+[edit]
+:%!xxd -r
+:wq
+
+To wakeup from deep sleep
+------------------
+
+Connect GPIO16 to Reset pin

examples/deepsleep/user/user_config.h

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+#ifndef _USER_CONFIG_H_
+#define _USER_CONFIG_H_
+
+#endif

examples/deepsleep/user/user_main.c

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+#include "ets_sys.h"
+#include "os_type.h"
+#include "osapi.h"
+#include "user_config.h"
+#include "user_interface.h"
+
+#include "driver/uart.h"
+
+#define INFO(...) os_printf(__VA_ARGS__)
+#define __SET__DEEP_SLEEP__WAKEUP_NO_RF__  system_deep_sleep_set_option(4)
+#define __SET__DEEP_SLEEP__WAKEUP_NORMAL__ system_deep_sleep_set_option(1)
+
+static ETSTimer report_timer;
+
+void ICACHE_FLASH_ATTR
+read_vdcc()
+{
+  uint16_t vdd33 = system_get_vdd33();
+  uint16_t vdd = vdd33*100/1024;
+  INFO("VDD = %d.%d\n", vdd/100, vdd%100);
+}
+
+//Init function 
+void ICACHE_FLASH_ATTR
+user_init()
+{
+  // UART setup
+  uart_init(BIT_RATE_115200, BIT_RATE_115200);
+  os_delay_us(2000000);     // 1 sec
+
+  read_vdcc();
+  __SET__DEEP_SLEEP__WAKEUP_NORMAL__; 
+  system_deep_sleep(5000000);
+}
+