peterjazenga nope, note the name psram, it is RAM, it cannot store data without power

peterjazenga some pins are 5v tolerant, applying 5v to other pins will kill the device it's onboard regulator allows you to use 5v sluts to the vin pin but never exceed 3.3v on the 3.3v pins

peterjazenga Arduino IDE meh but it depends on the goal, at software is powerful but also a complete pain to setup any project, for smaller projects, it's fine I'm using it with ADC DMA, complex timer controls and more without issue

peterjazenga stm32f103 has 3 serial ports, also supports 1 usb device port, can emulate keyboard, mouse and far more best programmed with st-link

peterjazenga NO This is AC only, the current transformer only handles AC, solar panels supply DC The output voltage of Solar panels varies widely depending on time of day, cloud and of course the type of installation but voltages up to 600v on larger arrays are not uncommon, this unit cannot measure those voltages

peterjazenga eg8010 is the control chip, Google it, as I haven't needed to use serial, I can't be more specific also it's logic level not rs232 voltage levels

peterjazenga Pumps do not heat water it is clear from the description details that the pump can handle water up to 100°C so it is suitable for circulating hot water

peterjazenga It is analog, it can be used with Arduino, STM32 or ESP32 for example but to measure AC current properly you must have a fundamental understanding of how it works, understand how to put a load resistor on this device, how to create a floating reference potential and do fast ADC You cannot use this device with slow ADC such as the ADS1115 Before using this, google, there are many examples of using this kind of sensor with Arduino and other boards