M5Stack Core2 boot loop after flashing CircuitPython 10.1+

[oenone]

I have an M5Stack Core2 and tried to flash the latest CircuitPython images, namely 10.2.0, 10.3.0-alpha1, and 10.1.4 - all of them resulted in a boot loop right after the output Serial console setup:

Serial console setup
ets Jul 29 2019 12:21:46

rst:0xc (SW_CPU_RESET),boot:0x17 (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:0x3fff0040,len:496
load:0x40078000,len:14128
load:0x40080400,len:3224
entry 0x40080568
Serial console setup

The newest version that successfully is booting, is 10.0.3:

Serial console setup
Adafruit CircuitPython 10.0.3 on 2025-10-17; M5Stack Core2 with ESP32
Board ID:m5stack_core2
UID:8712486A80C3
MAC:00:00:00:00:70:54

Auto-reload is on. Simply save files over USB to run them or enter REPL to disable.
code.py output:
Hello World!

Code done running.

Press any key to enter the REPL. Use CTRL-D to reload.

Adafruit CircuitPython 10.0.3 on 2025-10-17; M5Stack Core2 with ESP32
>>> 

I used esptool with default config to flash the images.

Did I miss a step or option?

[dhalbert]

Try a build artifact from #10922, in particular: https://github.com/adafruit/circuitpython/actions/runs/25389901159/artifacts/6813091322 for this board.

Do you see the same problem with other plain ESP32 boards?

[oenone]

the linked build results in boot loop, too.

I tried to find a board with similar MCU on the downloads page, and tried the "TTGO T-Display ESP32 16M by [LILYGO]" one - this doesn't enter the loop after flashing the 10.2.0 image:

Serial console setup
Adafruit CircuitPython 10.2.0 on 2026-04-22; LILYGO TTGO T-DISPLAY v1.1 with ESP32
Board ID:lilygo_ttgo_tdisplay_esp32_16m
UID:8712486A80C3
MAC:5C:F0:FC:3F:50:2E

Auto-reload is on. Simply save files over USB to run them or enter REPL to disable.
code.py output:
Hello World!

Code done running.

Press any key to enter the REPL. Use CTRL-D to reload.

[dhalbert]

The startup code for this board is quite complicated: https://github.com/adafruit/circuitpython/blob/main/ports/espressif/boards/m5stack_core2/board.c.

The way to debug this would probably be to make a debug build and look at the log output, and/or divide-and-conquer on the startup code and settings. It will be on our list. If you make builds yourself already you could try some of these things.

Also I'd do a bisect with versions between 10.0.3 and 10.1.4 to find which version transition started the crashing.

[oenone]

The 10.2.0 image for M5Stack Core (without the 2) works, too. I'll try to figure out how I can be more helpful to fix this, feel free to tell me how I can assist.