Helper function to format time register value to "HH:MM" string

Helper function to format date/time registers to ISO string

NOTE: my inverter (SPH4-10KTL3 BH-UP) only manages to read 64 registers in one read!

Helper function to verify register writes with retry Some Growatt firmwares commit values after a short delay

Constructor

Helper function to format complete time slot info

------------------------------------------------------- Check the Mqtt status and reconnect if necessary ---------------------------------------------