ESP32 Forum

Posted: **Wed Nov 12, 2025 4:02 pm**

Is it possible to use esptool.py for flashing non-IDF bare metal (without bootloader and partition) binaries?
I tried:

esptool --chip esp32c3 erase-flash
esptool --chip esp32c3 elf2image --flash-mode dio --flash-freq 80m --flash-size 2MB --min-rev 3 --min-rev-full 3 --max-rev-full 199 -o fw.bin fw.elf
esptool --chip esp32c3 --before=default-reset --after=hard-reset write-flash --flash-mode dio --flash-freq 80m --flash-size 2MB 0x0 fw.bin

But application won't work:

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ESP-ROM:esp32c3-api1-20210207
Build:Feb  7 2021
rst:0x7 (TG0WDT_SYS_RST),boot:0xf (SPI_FAST_FLASH_BOOT)
Saved PC:0x40052b02
SPIWP:0xee
mode:DIO, clock div:1
load:0x3fc84000,len:0x28
load:0x40384300,len:0x33c
load:0x00000000,len:0xfc64
load:0x42000000,len:0x11f04
entry 0x420000a4
Guru Meditation Error: Core 0 panic'ed (Illegal instruction)
Core 0 register dump:
PC      : 0x420000a4  RA      : 0x4004a296  SP      : 0x3fcde560  GP      : 0x00000000
TP      : 0x00000000  T0      : 0x00000000  T1      : 0x00000000  T2      : 0x3fcde59c
S0      : 0x00021f10  S1      : 0x00000030  A0      : 0x00000011  A1      : 0x0000000a
A2      : 0x00000000  A3      : 0x6000001c  A4      : 0x00000000  A5      : 0x420000a4
A6      : 0x80000000  A7      : 0x00000010  S2      : 0x00000000  S3      : 0x3fce0000
S4      : 0x0000ffff  S5      : 0x3ff1c14c  S6      : 0x00021f04  S7      : 0x3fcdf000
S8      : 0x00000000  S9      : 0x00000000  S10     : 0x00000000  S11     : 0x00000000
T3      : 0x00000000  T4      : 0x00000080  T5      : 0x30000000  T6      : 0x00000000
MSTATUS : 0x00001881  MCAUSE  : 0x00000002  MTVAL   : 0x00000000  INTLEVEL: 0x00000001

Generated file looks ok:

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esptool v5.1.0
Image size: 139056 bytes
Detected image type: ESP32-C3

ESP32-C3 Image Header
=====================
Image version: 1
Entry point: 0x420000a4
Segments: 4
Flash size: 2MB
Flash freq: 80m
Flash mode: DIO

ESP32-C3 Extended Image Header
==============================
WP pin: 0xee (disabled)
Flash pins drive settings: clk_drv: 0x0, q_drv: 0x0, d_drv: 0x0, cs0_drv: 0x0, hd_drv: 0x0, wp_drv: 0x0
Chip ID: 5 (ESP32-C3)
Minimal chip revision: v0.3, (legacy min_rev = 3)
Maximal chip revision: v1.99

Segments Information
====================
Segment   Length   Load addr   File offs  Memory types
-------  -------  ----------  ----------  ------------
      0  0x00028  0x3fc84000  0x00000018  DRAM
      1  0x0033c  0x40384300  0x00000048  IRAM
      2  0x0fc64  0x00000000  0x0000038c  PADDING
      3  0x11f04  0x42000000  0x0000fff8  IROM

ESP32-C3 Image Footer
=====================
Checksum: 0x30 (valid)
Validation hash: 12500cf2deba948c85f3ec323412a970312022db3b076e034661a651b5f7c3b9 (valid)

Start address is okay:

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readelf -h fw.elf | grep Entry
  Entry point address:               0x420000a4

Same ELF can be flashed with (older version) of esp-flash-rs:

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espflash flash -p /dev/esp32 fw.elf

Is there a way to flash bare-metal non-IDF application ELF to the ESP32-C3 with official tools?

Posted: **Wed Nov 12, 2025 4:30 pm**

You need all the other files that go along with the firmware: partition table, 2nd stage bootloader, etc. There is a function in esptool (merge_bin) to merge all the contents into a single file for easy distribution.
If you want to replace just the firmware on a device without touching the auxiliary files, you can use the parttool.py, which will inspect the partition table for you and then copy it over.
If you have a good image on a device that you then want to distribute, you can also just use esptool read_flash to write the whole flash contents into a single file.

Posted: **Wed Nov 12, 2025 5:29 pm**

I have non-C bare metal application which I want to run from flash of the ESP32-C3. I don't want to use bootloader nor partitions.

Flashing that application to the MCU works with unofficial tools. I am interested in doing that with official esptool (take .elf, do "something with it" and flash it to the flash of the MCU via UART).

ESP32 Forum

esptool for bare flashing bare metal-binary?

esptool for bare flashing bare metal-binary?

Re: esptool for bare flashing bare metal-binary?

Re: esptool for bare flashing bare metal-binary?