SAMD21 and a lot of compiler warnings

[CptHolzschnauz]

SAMD21 boards like the mkr series are not compatible.

[CptHolzschnauz]

Dear DF Robot Author Tang
I just went over the code. Please make it compatible with SAMD21 boards because it's hard to find a I2C wifi breakout.
It's not much (some wire.h problems / Software serial away examples) and you know your code best.

A lean version without all the thingspeak, onenet etc. routines would be very nice.
Just http and mqtt, UART / I2C seperate would be perfect, easier to read and maintain, also better for schooling etc.
THANK YOU in advance!