Chapter 6
Test verication
6.1 Power Consumption Verication
6.1.1 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 o and the information stored in CPU
will be lost. After ESP32 is woken up from Deep-sleep mode, it re-boots rmwares 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.
6.1.2 What sleep modes does ESP32 support? What is the dierence between them?
ESP32 supports three sleep modes: Modem-sleep, Light-sleep, and Deep-sleep.
• Modem-sleep: CPU works normally and the clock is congurable. The station (ESP32) automat-
ically turns on after it is connected to the AP. After ESP32 enters Modem-sleep mode, the RF
module is shut down, and the station remains connected 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 o 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 connected
to the AP in Deep-sleep mode.
Please refer to Table 8: Power Consumption by Power Modes in ESP32 datasheet for the corresponding
sleep power consumption.
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