Xiao-esp32c5 will not run without usb power

Products & Technology XIAO
,
1

I’m using Arduino to program a XIAO ESP32-C5, labeled 3/15/26.
I have a simple program up and running on Expansion Board v1.1 - when powered via USB C on the XIAO ESP32C5 module. I have a 3.7V LiPo battery connected correctly and it is charged to 4.15V.

The Arduino program does not use Serial.

When working, the program blinks the ESP32C5 user LED and writes to the I2C display on the expansion board. The ESP32C5 module has 3.39V on its 3V3 pin and 5.02V on USB5V pin.

The problem is: When I disconnect the USB-C from the ESP32C5, the program stops running. The ESP32C5 module has 3.39V on its 3V3 pin and 0V on USB5V pin. The I2C display keeps its last screen info.

I can power the ESP32C5 with a wall wort USB supply - and it works, it runs. It just doesn’t run of the battery alone.

I gotta be missing something, so if anyone can point me in a direction, I’m all ears.

2

are you sure the power switch on the expansion board is on?

also does your code have a serial! (serial + wait) command

serial! the exclimation point is wait meaning the code does not execute until a serial monitor connects.. HTH

3

Hi there,

So can you Use the code tgs above “</>” and paste your code in there,
We can look, I would bet the BSP or LIB version is the root cuase
Your display is a dead give away.

HTH
GL :slight_smile: PJ :v:

4

U8g2 is 2.36.19
Wire is 3.3.12
SPI is 3.3.12

#include <Arduino.h>
#include <U8x8lib.h>
#include <Wire.h>


// Libraries
// U8G2 by oliver, SSD1306 OLED display driver on expansion board


// Use HW I2C; adjust pin definitions if using XIAO nRF52840 or ESP32-C5 (SDA=D4, SCL=D5)
U8X8_SSD1306_128X64_NONAME_HW_I2C u8x8(/* reset=*/ U8X8_PIN_NONE, /* clock=*/ SCL, /* data=*/ SDA );   // OLEDs without Reset of the Display


void setup(void) {
  pinMode(LED_BUILTIN, OUTPUT);

//  Serial.begin(115200);

  u8x8.begin();
  u8x8.setFlipMode(0);
  u8x8.setFont(u8x8_font_chroma48medium8_r);

  u8x8.setCursor(0, 0);
  u8x8.print("XIAO Base Board");
  u8x8.setCursor(0, 2);
  u8x8.print("OLED Ready");
}

void loop(void) {

  // put your main code here, to run repeatedly:
  digitalWrite(LED_BUILTIN, LOW);
//  Serial.print("LED ON \n");
  u8x8.setCursor(0, 4);
  u8x8.print("LED ON  ");
  delay(2000);

  digitalWrite(LED_BUILTIN, HIGH);
//  Serial.print("LED OFF \n");
  u8x8.setCursor(0, 4);
  u8x8.print("LED OFF");
  delay(2000);

}

Thanks.

5

What type and capacity of battery are you using, and where is it connected?

6

Pkcell LP503562 1200mAh 3.7V connected to the Expansion Board battery JST connector.

7

OK, So , works plugged in or unplugged,

Keyboard and the floor…
:grin:
or battery ?

WIN_20261019_11_41_17_Pro
WIN_20261019_11_41_17_Pro1920×1080 285 KB

WIN_20261019_11_41_14_Pro
WIN_20261019_11_41_14_Pro1920×1080 286 KB

Had to press reset after the upload once unplugged.

HTH
GL :slight_smile: PJ :v:

(I flipped the display , my cable comes from the right) u8x8.setFlipMode(1);

8

OK, cool. I’m glad it works - on your desk PJ. ha

For clarity, it does not work on my desk.

Additional info:

  • I have tried 3 boards; Expansion, Round Display and a custom board - Only works with USB-C power for all 3 boards.
  • I have two ESP32-C5 modules and both exhibit the same issue.
9

check the battery power leads… the expansion board has + and - swaped from “typical” connectors

10

Hi there,

So , you are no crazy or the code is NOT bad, so. :grin: :+1:
If it was connected backards to the battery, then USB plugged in the Battery charger chip gives up the Ghost. You have any other Xiao’s on hand ?
I had this same scenario on a nRF52840 long ago, but exactly the same, CAN you tell if it charges the battery (meter) if the answer is NO, it’s not. then they are defective. “you may need to discharge the battery a little to get it to wake up”
hit support up for replacements. :crossed_fingers:

HTH
GL :slight_smile: PJ :v:

P.s. The nRF52840 like that, I have and it STILL works , no battery operation or charge but everything still works.

11

apply the 5V and ground directly to the pins, make sure the on off switch is not broken… several of my expansion boards the switch has broken due to shock damage. apply battery directly to the underside of the board

12

The Expansion Board v1.1 JST battery connector battery leads are good; + is plus and - is GND.

The switch works on the Expansion Board and the Round Display and are not broken.

Attaching the battery to the ESP32C5 BAT pins “works”, but it bypasses the power switch on the Expansion Board and the Round Display, so not a good solution.

For my custom board, I have attached +5V through a diode to the 5V pin and the same issue exists - only starts and runs with USB-C power applied.

Thanks for looking.

13

Yeah, I just tried an ESP32S3 with the Expansion Board example and it works as intended / expected.

After many USB-C plug/unplug iterations, the C5 occasionally worked without USB. Mostly not however. :frowning: Must be an edge condition somewhere.

Thanks.

14

This is my interpretation based on the circuit diagram.

When the expansion board is not receiving power from the USB
port, it generates 3.3V from the JST battery and supplies it to the XIAO’s 3V3 pin. However, since the 3V3_OUT pin on the XIAO_C5 is dedicated to outputting 3.3V, it cannot supply 3.3V to the XIAO’s internal circuitry. Therefore, the XIAO_C5 will not operate using the expansion board’s JST battery. The same issue occurs with the XIAO_nRF54LM20A.

15

WOW so this is a C5 thing…

16

Spot on.

A load switch, TPS22916CNYFPR, is labeled ‘backflow prevention’ on the XIAO ESP32C5 schematic block diagram.

There must be an edge case, or power supply bounce, or…, where removing USB power allows the load switch to remain enabled long enough to allow +3V3_OUT to backfeed to +3V3.

17

I confirmed with Seeed that in 2025 starting with the C5 the 3v3 is no longer an input voltage pin… SMH

18

Hi there,

So originally they only used it to power other sensors, USB and BAT were the main source of power. Wasn’t until someone got :grin: cute with the diode and back feeding the 3.3v directly ,then it was a 5v zener or something … started getting out of the rehlm.

So, I’m good with the way it used to work. makes more compatable to use it with a PMIC also. (you control the ON/OFF of the 3.3 volts for sensors & sleep)
:+1:

HTH
GL :slight_smile: PJ :v:

19

YES as my head was hitting the pillow i remembered the Great Diode Fudes

So you have to put a diode from the 3v3 to the 5v pin to allow power from the 3v3 pin to support power on 3v3 pin as in the expansion board battery power system.

this is because you can apparently apply 3v3 power to the 5v pin and it will pass thru the voltage regulator and power the XIAO.. BUT if you accidentally connect to USB the 5 v will backfeed

It pisses me off because they say.. “there was no standard” but the whole XAIO ecosystem is founded on the Expansion Board and the Book that was written in Germany to make the XIAO SAMD

Also it is a clone of the Adafruit Feather

So they distroy the whole ecosystem because someone was working on a toy gadget project… and they provided "USER FEEDBACK’ SMH

20

Good to know. Thank you.