Hi,
I'm new to forum and pi so please forgive stupid questions. I've a pi3 with which I'm building a weather station. I'm running it headless over a wireless network and windows PC for setup etc. To transmit data I plan to use a Adafruit Fona SIM 808 with GPS. I've wired it up as per tutorial, disabled serial port in raspi-config etc. On boot I tried using "screen" to access ttyS0 with "AT" command. Sometimes is comes back "OK" on first request then further commands get no response (including "AT" again). Sometimes is gives no response at all. Any ideas why and how to fix?