ESP32 为什么 WiFi 连接导致深度睡眠后“Brownout detector was triggered”

Question

When reconnecting to WiFi after waking up from deep sleep, an error "Brownout detector was triggered" is thrown causing the partial restart of the ESP. The setup phase is then done again, but now WiFi succeed to connect.

How to properly reestablish a WiFi connection after a deep sleep?

    #include <WiFi.h>
    #include "esp_wifi.h"
    
    #define SSID    "myssid"
    #define PASS    "ssidpass"
    
    #define uS_TO_S_FACTOR 1000000ULL   /* Conversion factor for micro seconds to seconds */
    #define TIME_TO_SLEEP  10           /* Time ESP32 will go to sleep (in seconds) */
    
    RTC_DATA_ATTR int boot_count = 0;
    
    void setup() {
      Serial.begin(115200);
      delay(200);
      
      print_wakeup_reason();
      Serial.print("Boot count: "); Serial.println(boot_count);
    
      Serial.println("WiFi connection");
      WiFi.begin(SSID, PASS);
      int try_count = 0;
      while (WiFi.status() != WL_CONNECTED && try_count < 10) {
          try_count++;
          delay(1000);
          Serial.println("Connection...");
      }
      Serial.println("WiFi connected");
    
      WiFi.disconnect();
      esp_wifi_stop();
      Serial.println("Sleeping in 1s ...");
      delay(1000);
    
      esp_deep_sleep(TIME_TO_SLEEP * uS_TO_S_FACTOR);  
    }
    
    void loop() {
    }
    
    void print_wakeup_reason(){
      esp_sleep_wakeup_cause_t wakeup_reason;
    
      wakeup_reason = esp_sleep_get_wakeup_cause();
    
      switch(wakeup_reason)
      {
        case ESP_SLEEP_WAKEUP_EXT0 : Serial.println("Wakeup caused by external signal using RTC_IO"); break;
        case ESP_SLEEP_WAKEUP_EXT1 : Serial.println("Wakeup caused by external signal using RTC_CNTL"); break;
        case ESP_SLEEP_WAKEUP_TIMER : Serial.println("Wakeup caused by timer"); break;
        case ESP_SLEEP_WAKEUP_TOUCHPAD : Serial.println("Wakeup caused by touchpad"); break;
        case ESP_SLEEP_WAKEUP_ULP : Serial.println("Wakeup caused by ULP program"); break;
        default : Serial.printf("Wakeup was not caused by deep sleep: %d\n",wakeup_reason); break;
      }
    }

Corresponding serial monitor message:

ets Jun  8 2016 00:22:57

rst:0xc (SW_CPU_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0018,len:4
load:0x3fff001c,len:1044
load:0x40078000,len:8896
load:0x40080400,len:5816
entry 0x400806ac
Wakeup was not caused by deep sleep: 0
Boot count: 0
WiFi connection
Connection...
WiFi connected
Sleeping in 1s ...
ets Jun  8 2016 00:22:57

rst:0x5 (DEEPSLEEP_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0018,len:4
load:0x3fff001c,len:1044
load:0x40078000,len:8896
load:0x40080400,len:5816
entry 0x400806ac
Wakeup caused by timer
Boot count: 0
WiFi connection

Brownout detector was triggered

ets Jun  8 2016 00:22:57

rst:0xc (SW_CPU_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0018,len:4
load:0x3fff001c,len:1044
load:0x40078000,len:8896
load:0x40080400,len:5816
entry 0x400806ac
Wakeup was not caused by deep sleep: 0
Boot count: 0
WiFi connection
Connection...
WiFi connected
Sleeping in 1s ...
ets Jun  8 2016 00:22:57

rst:0x5 (DEEPSLEEP_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0018,len:4
load:0x3fff001c,len:1044
load:0x40078000,len:8896
load:0x40080400,len:5816
entry 0x400806ac
Wakeup caused by timer
Boot count: 0
WiFi connection

Brownout detector was triggered

I'm using a ESP-WROOM-32 (Chip is ESP32D0WDQ6 (revision 1)), on GNU Linux, with Arduino IDE 1.8.13, card library: Espressif System 1.0.4

Answer 1

This is a power problem. You need a more capable power supply to feed the ESP32. If using a USB-powered dev board, try replacing the USB cable and connecting it directly to a USB port on your computer. A powered USB hub might also help.

Answer 2

As my cable is undoubtedly good, I persevered and found this solution on the Net. Does the fault come from the component which is a copy and not an genuine? Mystery.

#include "soc/soc.h"
#include "soc/rtc_cntl_reg.h"

void initialize() {
    WRITE_PERI_REG(RTC_CNTL_BROWN_OUT_REG, 0);
}

Answer 3

I was having the same problem, has it has been mentioned that it is a power related problem I changed my power source from 2.0 to 3.0 and the problem was sorted out.

Answer 4

So I'm seeing this problem too. "Brownout detector was triggered" on my ESP32-S2-WROOMD (DevKit). It happens when WiFi.Begin is called but only when my ESP32 DevKit is loaded: meaning I am using the 3.3V rail for powering some GPIOs and I'm also using a 5V sensor.

Thinking the USB(2 and 3) ports weren't driving enough voltage/current I moved from the USB source to a separate regulated 5V power supply. This seemed to drive both the MCU and the peripheral lines well but I was still getting intermittent brown-outs.

Then I added a polarized 220uF capacitor across the 5V positive/negative source and that all but eliminated the issue for me. BUT is still happens occasionally and unfortunately randomly.

My rig includes an EPROG/JTAG debugger board with PlatformIO. Thinking the board might also be contributing I disconnected the debug board and that seems to have solved my problem (I didn't want to try to disable the brownout detector btw).

So, my thinking candidly is that the ESP32-S2 is very sensitive and finicky to power fluctuations which don't normally occur when the MCU is standing alone or simply connected with a sensor or two, but when you "load" it and there are power fluctuations (even when powered externally and not via USB) the chip has issues. BTW, I even dialed up the regulated power source to 5.5V to see if additional juice would solve the problem and still didn't 100% cure.

Thinking of moving to the newer S3....

Answer 5

In the search for the lowest consumption, I finally proceeded to various optimizations. And I came to deep sleep the ESP after disabling WiFi, and I take the ESP out of deep sleep with the WiFi still disabled. I reactivate the WiFi before using it. The ESP wake-up time is not a problem, low consumption is my priority. And it works without a problem, without even using the first solution I posted.