This is a port of the Open DFU Bootloader by Nordic Semiconductor to the Lilygo T-Echo.
With this bootloader flashed to your T-Echo, you can update the firmware using the USB-C connector and nrfutil.
Suppose you have built a new firmware version and want to flash it to a device
where this bootloader is already installed. To do that, you first need to
create an update image. A script is provided to simplify that (example for the
lora-aprs firmware):
scripts/create_package.sh ../lora-aprs/_build/nrf52840_xxaa.hex test.zipTo flash an image, you first need to invoke the bootloader as follows:
- Press and hold the lower push button on the T-Echo.
- Momentarily press the upper push button (reset).
- Release all buttons.
The LED should now be fading in green to indicate that the bootloader is active.
Connect the T-Echo to your computer via USB and check dmesg for the interface
name (should be something like /dev/ttyACM0). Then run the flash script:
scripts/flash_package.sh /dev/ttyACM0 test.zipThis bootloader does not provide any security for firmware updates. Even though the packages are signed that signature is not checked by the bootloader. So basically anyone with physical access to your device can flash any firmware.
For simplicity (to make the scripts above directly usable) a default private key, which is used to sign the packages, is provided in this repository.
However, when the bootloader itself is update through DFU, the signature is checked. So, if you want to make sure only you can overwrite the bootloader via USB, you must not use the default key and generate your own keypair instead.
If you really need/want signature checks for regular firmware updates, feel free to port the Secure Bootloader for the T-Echo based on this version and generate your own keypair.
As the modifications from Nordic’s version of the Open DFU Bootloader are minimal, this version is licensed under there license. See the file headers for details.