Arduino UNO & SIM900 -AT communicaton problem

AWOL:

are never any readable text.

...usually implies either a speed mismatch, or a line inversion.

I checked these speeds and matched them to the speed of the Efcom Pro (what it says in the product description... is there any way to check it?):

  • serial port (in Windows hardware manager)
  • serial monitor

Do I need to check in other places as well?

looks more like the -1 that a serial read rturns if there is no data to read.

The thing is, it sends this only when the chip is powered on, then it stops. So I interpret it as the "hello, i'm ready signal" of the chip...