Today my two Delock 11827 "WLAN Power Socket Switch"es arrived and after I successfully configured them for my WiFi, I checked the installed tasmota version, which identified itself as 6.5.0. So it was quite old and deserves an update.
At the time of writing this, version 10.0.0 was the current release (http://ota.tasmota.com/tasmota/release/)
tasmota follows a strict upgrade-flow when doing upgrades over several major versions. The ususal upgrade-flow will not work straight with the plug, as due to limited flash-memory we have to take the long road by flashing the minimal versions before upgrading to the full version. The flow will look like this:
6.5.0 --> 6.7.1 --> 8.5.1 (minimal) --> 8.5.1 --> 9.1.0 (minimal) --> 9.1.0* --> 10.0.0** (minimal) --> 10.0.0**
You'll find the releases on the tasmota github: https://tasmota.github.io/docs/Download/
* I did not use the intermediate release 9.3.1, as it did not install properly
** The current version of tasmota does not have the version number in the filename
Use the "bin"-versions for minimal and full (example for current version). Simply copy the respective OTA-URL and paste it to the OTA-field in the firmware upgrade webinterface of the plug.
1. Update with the latest Delock firmware
Delock provides the firmware for the 11827 on their webserver. As I was not able to find a link on their entire website, I put it here: https://www.delock.de/download/firmware/11827de.bin
The filename does not indicate a version, but actually it contained an upgrade to 7.2.0 to the original 6.5.0.
I downloaded the file and flashed the first plug via the webinterface, not using the OTA option. The second one I did with the OTA upgrade using the same link. Both worked fine.
2. Start the upgrade-flow
Reset the plug
Flash minimal version first
This takes a moment and the web-interface will become unresponsive in a time. After it comes back, the screen shows a warning about the minimal-firmware-version:





