[SOLVED] SIM900 strange behaviour

You may see it on screenshot. On “AT&F=0” nothing happens.

Fixed it by “AT&F0” command when SIM ejected. But what it was?

It's a power supply issue. 0.5 Ah is too low for SIM900+PIR+Relay.

I attached my HM-10 configuration code:

That does not tell us what you typed into the application that is sending data to the Arduino.


Again, we have no idea what kind of data you are sending. "12, 23!" will parse much faster than "12, 23". The lack of a non-digit at the end means that parseInt() will keep waiting, hoping for more digits to arrive.