Power Consumption Verification


Why does ESP32 reboot when it is woken up from Deep-sleep mode?

When ESP32 is in Deep-sleep mode, the digital core is powered off and the information stored in CPU will be lost. After ESP32 is woken up from Deep-sleep mode, it re-boots firmwares and re-loads them to the internal memory. The application information that requires to be reserved can be saved in RTC as RTC is still powered on in Deep-sleep mode. The reserved information can be loaded after wake-up.

Which sleep modes does ESP32 support? What is the difference between them?

ESP32 supports three sleep modes: Modem-sleep, Light-sleep, and Deep-sleep.

  • Modem-sleep: CPU works normally and the clock is configurable. The station (ESP32) automatically turns on after it is connected to the AP. After ESP32 enters Modem-sleep mode, the RF module is shut down, and the station remain connection to the AP. If ESP32 disconnects to the AP, it will not work in Wi-Fi Modem-sleep mode. In Modem-sleep mode, the CPU clock frequency can be lowered to further reduce the current consumption.

  • Light-sleep: CPU is suspended and the digital core clock is limited. When ESP32 is in Light-sleep mode, not only the RF module is closed, CPU and partial system clocks are also suspended. After ESP32 exits Light-sleep mode, the CPU resumes working.

  • Deep-sleep: The digital core is powered off and the information stored in CPU is lost. After ESP32 enters Deep-sleep mode, all modules are closed except for RTC. After it exits Deep-sleep mode, the entire system restarts, which is similar to the system reboot. ESP32 does not remain connection to the AP in Deep-sleep mode.

Can ESP32 in Deep-sleep mode be woken up by any RTC_GPIO?

Yes. For the configuration of RTC_GPIO, please refer to ESP32 datasheet > Chapter Pin Definitions > Section Pin Description.

What is the power consumption of ESP8266 when the CHIP_PU pin is at the low level?

  • CHIP_PU pin is the module EN pin. When the pin is set to the low level, the power consumption of the chip is about 0.5 μA.

  • In Table Power Consumption by Power Modes of ESP8266 Datasheet, shut down power mode means CHIP_PU is pulled down and the chip is disabled.