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Flash STM32 Devices

Flashing Methods for STM32 Devices​

Flashing an STM32WL board takes two steps: get the board ready to flash, then write the firmware. A UART flash uses the chip's built-in ROM bootloader; an SWD programmer writes to flash directly. Meshtastic firmware for STM32WL targets is distributed as firmware-<target>-X.X.X.xxxxxxx.bin and flashed to 0x08000000; the .elf in the same release also works with STM32CubeProgrammer.

For the BOOT0 pin location, UART pins, and any board-specific steps, see the documentation for your board.

Getting the Board Ready to Flash​

STM32WL has no USB DFU mode. For a UART flash, the ROM bootloader can be entered from a Meshtastic client or with the BOOT0 pin. For an SWD flash, the programmer resets and connects to the board itself.

Flashing from Web Flasher​

Browser-based flashing is a work-in-progress and not available for STM32 targets yet.

Flashing over UART​

A USB-TTL serial adapter can flash STM32WL over UART without an SWD programmer, once the board is in the ROM bootloader.

Flashing over SWD​

An SWD programmer such as an ST-LINK writes firmware straight to flash over the SWD pins, without using BOOT0 or the ROM bootloader.

Flashing over USB​

STM32WL has no USB peripheral, so there is no USB DFU mode. A UART flash (through the ROM bootloader) and an SWD flash are the only options.

Any USB port connects to an internal USB-to-UART bridge and can be used for UART flashing, unless that bridge is not wired to a bootloader UART. On the Wio-E5 it is not, though two jumper wires can bridge it to one; see the Wio-E5 page.

Removing Readout Protection​

Some boards, such as the Wio-E5, ship with flash readout protection enabled. STM32CubeProgrammer connects but cannot read or write flash until readout protection is removed.