[BUG] ESP32-C3 Boot Loop (RTCWDT_RTC_RST) on Shelly 1PM Mini Gen3

[jarcos-al]

Hello,

I'm experiencing a persistent boot loop (rst:0x10 RTCWDT_RTC_RST) on a new Shelly 1PM Mini Gen3, which uses an ESP32-C3 chip.

Crucial Diagnostic Information:

The hardware is confirmed to be 100% functional. The problem is specific to the Tasmota firmware.

• A minimal "Blink" sketch from the Arduino IDE works perfectly.

• A full ESPHome configuration also compiles, flashes, and runs perfectly on the device.

Troubleshooting Steps Performed:

I have exhaustively tried to solve this issue without success. The boot loop persists after every single one of these steps:

1. Performing a full erase_flash before every attempt.

2. Using the latest official pre-compiled Tasmota release (tasmota32c3.bin and tasmota32c3.factory.bin).

3. Compiling from the latest source code.

4. Forcing board_build.flash_mode = dio.

5. Testing different upload speeds (e.g., 921600 and 115200).

6. Compiling without a default device template applied.

7. Compiling a "scorched earth" minimal build with most features (WEBSERVER, MQTT, SCRIPT, etc.) disabled via user_config_override.h.

None of the above has changed the outcome. The device enters a boot loop immediately after flashing Tasmota.

Boot Loop Log:

ESP-ROM:esp32c3-api1-20210207
Build:Feb 7 2021
rst:0x10 (RTCWDT_RTC_RST),boot:0xd (SPI_FAST_FLASH_BOOT)
SPIWP:0xee
mode:DIO, clock div:1
load:0x3fcd5820,len:0x98
load:0x403cc710,len:0x874
load:0x403ce710,len:0x21bc
entry 0x403cc710

...
It seems there is a fundamental incompatibility between the Tasmota core and this specific hardware revision. I'm happy to provide more information or perform further tests if needed.

Thank you for your hard work on this project.

[s-hadinger]

The logs you are showing are early boot processes, Tasmota seems to not have even started. Did you try earlier versions with and without cdc?

[sfromis]

You did not give details of exactly how you were doing the flashing. The Tasmota Web Installer recommended, leaving the firmware variant to default (will automatically detect chip variant), only selecting the serial port when prompted.

[jarcos-al]

I also tried the option of flashing via Tasmota Web Installer, getting the same result. El El lun, 11 ago 2025 a las 9:15, sfromis ***@***.***> escribió:

…

You did not give details of exactly *how* you were doing the flashing. The Tasmota Web Installer <https://tasmota.github.io/install/> recommended, leaving the firmware variant to default (will automatically detect chip variant), only selecting the serial port when prompted. — Reply to this email directly, view it on GitHub <#23776 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AQS2A4C4EKZ5URLSTVTLEGT3NA7KLAVCNFSM6AAAAACDR6YOVGVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTIMBWHA3DCOA> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[sfromis]

Is your Shelly 1PM Mini Gen3 with support for Matter? In that case, it may have boot security preventing firmware replacement.

[jarcos-al]

No, it had the official Shelly firmware version 1.5.1.

[jarcos-al]

I will try this option. I will comment on the results. El El lun, 11 ago 2025 a las 8:02, s-hadinger ***@***.***> escribió:

…

The logs you are showing are early boot processes, Tasmota seems to not have even started. Did you try earlier versions with and without cdc? — Reply to this email directly, view it on GitHub <#23776 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AQS2A4B3XN5TAAPD3XD4SET3NAWYLAVCNFSM6AAAAACDR6YOVGVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTIMBWHAZDEMY> . You are receiving this because you authored the thread.Message ID: ***@***.***>