Brownout during wifi startup

[tehKaiN]

Hardware:

Board: ESP-WROOM-32 + breakout board
Core Installation/update date: 8/jun/2016
IDE name: Platform.io
Flash Frequency: ?40Mhz?
Upload Speed: 115200

Description:

I'm developing ESP32-based module for board which has 500mA 3v3 power supply.

After using code attached below, each time during WiFi startup I get brownout. On scope there is quite big voltage drop. This doesn't happen on a breadboard with larger capacitor attached (470uF), so you could assume that's the problem, however AT firmware from https://github.com/espressif/esp32-at works flawlessly under same electrical conditions and starts WiFi without any problems. Unfortunately this firmware is closed source, so my question is: what can I do differently to reduce init voltage drop to have same results as in AT firmware?

I've tried esp_wifi_set_max_tx_power but it works only after esp_wifi_start() but then it's too late to make any difference.

Also, at first I've tried using Arduino functions for Wifi, but they result in brownouts too.

Sketch:

#include <Arduino.h>
#include "esp_wifi.h"

#define SSID "ESP32AP"

void setup() {
	wifi_init_config_t wifiInitializationConfig = WIFI_INIT_CONFIG_DEFAULT();

	esp_wifi_init(&wifiInitializationConfig);

	esp_wifi_set_storage(WIFI_STORAGE_RAM);

	esp_wifi_set_mode(WIFI_MODE_AP);

	wifi_config_t ap_config;
	strcpy((char *)ap_config.ap.ssid, SSID);
	ap_config.ap.channel = 0;
	ap_config.ap.authmode = WIFI_AUTH_OPEN;
	ap_config.ap.ssid_hidden = 0;
	ap_config.ap.max_connection = 1;
	ap_config.ap.beacon_interval = 100;

	esp_wifi_set_config(WIFI_IF_AP, &ap_config);

	esp_wifi_start();
}

void loop()
{
}

Debug Messages:

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:0x3fff0010,len:4                     
load:0x3fff0014,len:588                    
load:0x40078000,len:0                
load:0x40078000,len:9768                          
entry 0x400789b8

[me-no-dev]

The Arduino WIFi.* call the same IDF functions above, so difference will not matter. In AT probably the power is lowered in another way.

I can advise you to do two things:

• get better LDO that can handle more current so it does not lead to such voltage drop
• submit an issue in IDF's repository, so engineers can look at the AT firmware and see what is different (the firmware might also be compiled with older IDF/sdkconfig and not having the brownout code inside)

[PRO2XY]

Hey! I was facing the same issue with brownout detector restarting the ESP32.
I'm pretty sure it might be a hardware issue, even though I have ruled out the power supply capacity, solder joints, capacitors, etc. I am thinking maybe it's some bad solder joint inside the ESP-WROOM-32 module itself. I intend to take the metal shield off and check for the same, and if nothing else, then solder the VDD3P3_RTC up to 3V3 pad on the module directly. Or maybe some other black magic.

But, until then I used this as a workaround, and thought it may be of help to you.
#include "soc/soc.h"
#include "soc/rtc_cntl_reg.h"
void setup(){
WRITE_PERI_REG(RTC_CNTL_BROWN_OUT_REG, 0); //disable brownout detector
.... other stuff ...

Needless to say that this will disable the brownout detector completely, so if you do have power related issue you will just get GURU MEDITATION ERROR(s) of sorts. (I wonder how the name came to be so..!)

Edit: Maybe #675 could use this too.

[Redferne]

Amiga 4ever! 😎

[tehKaiN]

@PRO2XY That solved a problem for me. Thanks!

[Bartimaeus-]

I had a similar problem when trying to use the WiFi when powered from USB on a dev board that had inputs for USB power and 12v. The inputs went to the same LDO through some OR'ing diodes:

When the board was powered from 5v, there was enough of a drop across the OR'ing diode to cause the 3.3v output to dip to 2.3v:

If your board has a similar setup then choosing different diodes could fix the problem, but as @me-no-dev suggested getting a better LDO (or better yet a switching power supply) is a better long term solution. My short term solution was to power the board from a bench supply set to 5.5v so the drop across the diode wouldn't affect the output of the LDO.

The workaround posted by @PRO2XY is not an actual fix to this problem, it just hides some of the symptoms. Turning off the brownout detector is like taking the batteries out of a carbon monoxide alarm because you're getting a headache. There are all sorts of unpredictable behavior that can start showing up in a brownout condition that may not be caught be other alarm functions (that's why the brownout detection exists). Just a word of caution for those who might not know any better reading this thread.

[what78what]

@PRO2XY, great post, thanks! Helped.

[PRO2XY]

What @Bartimaeus- has written about BOD is true. It is only going to mask the problem and let you go a little further. It is not going to solve anything at all!
I can say with almost 100% certainty that anyone looking for a solution in this thread has an issue with the power supply circuit, and most probably it is what @Bartimaeus- noted in his comment.

[szuercher]

If you soldered by your self, also check the GND connection, they are hard to solder. Soldering GND on the thermal pad solve my problem.

[StuartsProjects]

I had built myslef a nice little board for an ESP32, with a LoRa device, 2kbyte FRAM, TC74 temperature sensor and 0.98" OLED display the sleep current is 8uA. The regulator was a HCT7333 (250mA) which worked fine until I tried the WiFi, this regulator could not cope with the startup current pulse and a brownout resulted.

Fortunatly the PCB also allowed for a MCP1825 (500mA) regulator to be fitted which can cope with the current pulse although its standby current is a little too high at 120uA.

[bobesp32]

I HAD THE SAME EXACT PROBLEM, MY FIX WAS EASY, ALL I DID WAS USE A NEW (AND BETTER) USB CABLE - MY PROBLEM WAS GONE!
HOPE THIS HELPS.

[cybergogo]

Hi all,
just wanted to share my experience.
i'm using an ESP-32S, classic, with the white breakout PCB which only has 2 buttons and resistors.
Had huge difficulty to make it work, crashing at each wifi init.
Was using an LM2596 voltage regulator, no luck. Added various capacitors, no luck.
In the end, an AMS1117-3.3v solved the issue. maybe the variable LM2596 was too variable. I don't know, but it works now...

[philbowles]

@PRO2XY : The Guru Meditation is an error notice displayed by early versions of the Commodore Amiga computer when they crashed. It is analogous to the "Blue Screen of Death" in Microsoft Windows operating systems, or a kernel panic in Unix