diff --git a/include/espressif/esp_system.h b/include/espressif/esp_system.h
index e37263e..155489e 100644
--- a/include/espressif/esp_system.h
+++ b/include/espressif/esp_system.h
@@ -42,6 +42,7 @@ enum sdk_sleep_type sdk_wifi_get_sleep_type(enum sdk_sleep_type);
 
 void sdk_system_restore(void);
 void sdk_system_restart(void);
+bool sdk_system_deep_sleep_set_option(uint8_t option);
 void sdk_system_deep_sleep(uint32_t time_in_us);
 
 uint32_t sdk_system_get_time(void);
@@ -57,6 +58,32 @@ bool sdk_system_rtc_mem_read(uint8_t src, void *dst, uint16_t n);
 bool sdk_system_rtc_mem_write(uint8_t dst, const void *src, uint16_t n);
 
 void sdk_system_uart_swap(void);
+void sdk_system_uart_de_swap(void);
+
+#define SYS_CPU_80MHZ   80
+#define SYS_CPU_160MHZ  160
+/*
+   Set CPU frequency in MHz. All peripheral devices are clocked by independent
+   system bus, and CPU frequency change will not affect them.
+ */
+bool sdk_system_update_cpu_freq(uint8_t freq);
+uint8_t sdk_system_get_cpu_freq(void);
+
+/*
+   Measure voltage on the TOUT pin, 1V max. Returns 10 bits ADC value (1/1024V).
+   Voltage range 0 .. 1.0V. RF must be enabled.
+   Example:
+      printf ("ADC voltage %.3f", 1.0 / 1024 * sdk_system_adc_read());
+ */
+uint16_t sdk_system_adc_read(void);
+/*
+   Measure power voltage. Returns 10 bits ADC value (1/1024V).
+   TOUT pin must be floating and RF must be enabled.
+   Example:
+      printf ("Power voltage %.3f", 1.0 / 1024 * sdk_system_get_vdd33());
+ */
+uint16_t sdk_system_get_vdd33(void);
+
 
 #ifdef	__cplusplus
 }