Long time, no see! For different reasons, the project was on hold obviously.
There were a few working prototypes but not time for further development.
But good news: Together with my brother we revisited the project in our winter vacations and took advantage of new components that are available nowadays.
In detail: we now use an ESP32 instead of the ESP8266 and were able to ditch the additional AVR. The job of the AVR is now done by the inbuilt ULP (ultra low power) co-processor of the ESP32! We use the knowledge @derflob has gathered with his ultra low power soil monitor.
Also, we settled down to a 18650 LiFePO4 battery. With its maximal voltage of 3.6V it is a perfect fit for the ESP32 to use without an additional LDO. They are now available with real 1800 mAh.
We also integrated an USB-C charging port and an USB to serial chip.
There are sensors for humidity and pressure (BME280 as before) and a better sensor for temperature (TMP117). Also the light sensor was updated to an OPT3001. For PIR sensor we use the EKMA and the successor EKMB as there are no other reliable and easy to use low power PIRs
And for the sake of "why not?" there is also an accelerometer (KX023-1025).
Here is a first glimpse of the pcb (the big void is for the battery) and protoypes are already ordered!
We will keep you updated!
See also our blog at https://blog.m3k.cc