Hey,
have a look at attachment Mega2560.jpg, PIN 19 is RXD on Arduino, while 18 is TXD.
On the other attachment Sim808.jpg, left PIN is TXD and right PIN is RXD (at least I interpret the info on the right like that)
It would make sense to connect RXD <-> TXD and TXD <-> RXD, but if I do so, the SIM808 start smoking - A LOT.
While if I connect RXD <-> RXD and TXD <-> TXD it works fine and Arduino can communicate with GSM module.
My question is simple: Why will the reasonable setup killing my SIM808???
Second question: Why is it smoking? Kinda loop? (I'm a programmer, not an electrician)
Thanks,
Recy
