My quick notes regarding a SIM800L module on an inexpensive SIM800L EVB “SIM800LV2.2” carrier board from eBay. Communicates happily with a computer through a generic USB<>TTL converter, 5V logic levels and 5V power at 9600 baud. Carrier board includes a TTL level shifter and 2 diodes in series to drop the voltage from 5V to ~3.6V.

Command snippets

Sending SMS

AT+CMGF=1                # Set modem to text mode
AT+CMGS="phone_number"   # Start composing a message to phone_number

The second command will open a message composing mode, CTRL+Z to send.

Receiving SMS

AT+CMGF=1       # Set modem to text mode
AT+CMGL         # List unread received texts
AT+CMGL="ALL"   # List all received texts, read or not
AT+CMGR=<id>    # Get a message with id


ATD+ phone_number;  # Dial phone_number
ATH                 # Hang up
ATA                 # Accept incoming call

Misc commands

AT+CNETSCAN      # Scanning for neighbouring cells
AT+GSV           # Show module information
AT+CNUM          # Show SIM phone number
AT+CSQ           # Show signal levels
AT+CCLK          # Show current date/time
AT+COPS?         # Show which operator the module is connected to

Full AT commands documentation for this chipset: SIM800_Series_AT_Command_Manual_V1.09