This picture shows my current development ratnest of a moisture sensor connected to a LoRa unit. It’s a few extra components that have nothing to do with this project, but it’s a good reminder why I seldom do breadboard ratnests anymore. The wiring failure trate is very high, but in this case it worked out well as I needed to test the moisture sensor and the LoRa unit (bottom left). I will put out a PCB for this soon. I decided to use a Blackpill that is a dip 40 breakout with a STM32F401CC on it. It has space for a SPI FLASH/FRAM on the back and have RTC oscillator etc. For it’s low price it is good value and an easy way around the current component shortage.
STM32F401CC is not low power, but my main concern here is the other components.