Hello everyone,
I'm quite new to ESP32 development. I've been using this devkit for a few small projects and everything was going smoothly until I decided to run it on battery. In particular, the ESP32 devkit I'm using, when connected to a battery, seems to have issues when trying to connect to the Wifi.
I'm using a 9V battery connected to a MB-V2 power supply to convert the output voltage to 3.3.V. The power supply board has the following specifics:
- Input voltage: 6.5-9v (DC) via 5.5mm x 2.1mm plug
- Output voltage: 3.3V/5v
- Maximum output current: 700 mA
- Independent control rail output: 0v, 3.3v, 5v to breadboard
As you can see in the picture, my multimeter measures an output voltage of about 3.3V
I built a sample project for debugging, here's the schematics:
The battery is connected to the power supply which outputs 3.3V and powers the ESP32 through its 3.3V pin. I don't have a schematic for this specific devkit I'm using so the devkit used in the schematics is the DOIT one, hence all of the pins are off. The code is quite simple, though, so it hopefully can clear things a bit:
#include <WiFi.h>
const int uS_TO_S_FACTOR = 1000000;
const int TIME_TO_SLEEP = 3;
const int RED_LED_PIN = 32;
const int BLUE_LED_PIN = 25;
const int YELLOW_LED_PIN = 26;
const char SSID[] = "SSID";
const char PASS[] = "PASS";
void startupSequence(){
digitalWrite(RED_LED_PIN, LOW);
digitalWrite(BLUE_LED_PIN, LOW);
digitalWrite(YELLOW_LED_PIN, LOW);
// Sequence
digitalWrite(RED_LED_PIN, HIGH);
digitalWrite(BLUE_LED_PIN, HIGH);
digitalWrite(YELLOW_LED_PIN, HIGH);
delay(1000);
digitalWrite(RED_LED_PIN, LOW);
digitalWrite(BLUE_LED_PIN, LOW);
digitalWrite(YELLOW_LED_PIN, LOW);
delay(500);
}
void setup(){
Serial.begin(115200);
while(!Serial){}
pinMode(RED_LED_PIN, OUTPUT);
pinMode(BLUE_LED_PIN, OUTPUT);
pinMode(YELLOW_LED_PIN, OUTPUT);
startupSequence();
delay(500);
digitalWrite(RED_LED_PIN, HIGH);
delay(1000);
Serial.print("Connecting to ");
Serial.println(SSID);
WiFi.begin(SSID, PASS);
while ((WiFi.status() != WL_CONNECTED) && (millis()<10000)) {
Serial.print(".");
delay(500);
}
Serial.print("Connected. IP: ");
Serial.println(WiFi.localIP());
digitalWrite(RED_LED_PIN, LOW);
if(WiFi.status() == WL_CONNECTED) //Run this only the first time
{
Serial.println("Connected");
digitalWrite(YELLOW_LED_PIN, HIGH);
} else
{
Serial.println("Not connected");
digitalWrite(BLUE_LED_PIN, HIGH);
}
delay(3000);
digitalWrite(BLUE_LED_PIN, LOW);
digitalWrite(YELLOW_LED_PIN, LOW);
Serial.println("Going to sleep");
esp_sleep_enable_timer_wakeup(TIME_TO_SLEEP * uS_TO_S_FACTOR);
esp_deep_sleep_start();
}
void loop(){}
In the code, the ESP32 first lights up all LEDs, then it lights up the red LED while it tries to connect to the Wifi. After at most 10 secs, it lights up the yellow LED if it successfully connected, otherwise it lights up the blue LED. Also, as a last thing I send the ESP32 into deep sleep, as my intention was to measure its power consumption during sleep.
When connected to the PC, everything runs smoothly, while when connected to the battery the ESP32 (apparently) never exits the while loop and the red LED stays always on. The RED led then starts flickering and the power LED start blinking. Resetting it throught the RST button on the devkit causes the power LED to start blinking and the red LED never lights up. This continues until I cut off the power, then the code seems to start again from the beginning (i.e. the startup sequence) and the this behavior repeats.
I've read a few posts about similar issues with ESP32 devkits, but the problem was always about batteries not having high enough voltage, which doesn't seem to be my case. What could be causing the issue?
