What does gsmAccess() function do (GSM.h and Arduino)

I have a module which connects and sends ussd through arduino+GSM shield. I am kind of fuzzy on the following two commands which are commented with ??. (line 4 and line 7).

Can someone explain what these two do?

And plus gsmAccess.getStatus() == 3; what are the other values that this function can return apart from 3?

#include <GSM.h> #include <GSM3ShieldV1DirectModemProvider.h> GSM3ShieldV1DirectModemProvider modemAccess; GSM gsmAccess(true); // ?? void sendCommand(String com){ // com is "AT+CUSD=1,\"#366#\",\0" if(gsmAccess.getStatus() == 3) // ?? Serial.println(modemAccess.writeModemCommand(com,comDelay)); else{ connectModule(); sendCommand(com); } } 

1 Answer

The line:

GSM gsmAccess(true); 

initializes the GSM library to enable an Arduino to act as though it were a mobile (cell) phone. The true parameter puts the library into debug mode which will print out all the AT commands from the modem (reference).

The line:

if (gsmAccess.getStatus() == 3) 

is checking that the GSM library is ready to send commands. The 3 is the code for GSM_READY as defined in the source code

For clarity it would be better to write this line as:

if (gsmAccess.getStatus() == GSM_READY) 

The other statuses (defined in the same source file) are:

0: ERROR 1: IDLE 2: CONNECTING 3: GSM_READY 4: GPRS_READY 5: TRANSPARENT_CONNECTED 6: OFF