Firmware Tips and Tricks

Firmware
28

Getting out of DFU mode without manual resetting of overwriting the current firmware

NOTE: Tested with a Photon.

As specified in an old post titled [Getting out of DFU mode], and in the Photon documentation, the only ways to get out of the DFU mode are by manually reseting the Photon of by writing a firmware with the :leave option.

The trick here is to use the dfu-util writing a 0 byte firmware with the :leave option to force the reboot that gets out the Photon from the DFU mode, preserving the current firmware and keys configuration.

For the Photon:

$ dfu-util -d 2b04:d006 -a 0 -s 0x080A0000:leave -D /dev/null

For the Core:

$ dfu-util -d 1d50:607f -a 0 -s 0x08005000:leave -D /dev/null

The addresses specified are the respective userFirmware addresses of the Photon and Core, which firmwares are actually not overwritten.

On the other side we can add a function to our firmware to enter in DFU mode by code (without pressing any Reset+Setup button combination). The advantage is that we won’t need to leave access to the physical buttons to enter in DFU mode (remotely), then write custom data by USB to the internal or external memory using several calls to dfu-util without the :leave parameter, and finally force a reboot to get out of the DFU mode (using this trick).

// Force enter in DFU mode
int enterDFU(String param) {
    System.dfu();
    return 0;
}

or forcing a persistent DFU mode that will remain after a power-cycle, and only would get out by using the :leave option:

// Force enter in persistent DFU mode
int enterPersistentDFU(String param) {
    System.dfu(true);
    return 0;
}

This option could also be added in future releases of particle-cli, if you consider it of enough interest.

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