Examples > GSM library
This sketch send a SMS message from an Arduino with a connected GSM shield. using the serial monitor, you'll enter the number to connect with, and the message to send.
First, import the GSM library
SIM cards may have a PIN number that enables their functionality. Define the PIN for your SIM. If your SIM has no PIN, you can leave it blank :
#define PINNUMBER ""
Initialize instances of the classes you're going to use. You're going to need both the GSM and GSM_SMS class.
setup, open a serial connection to the computer. After opening the connection, send a message indicating the sketch has started.
Create a local variable to track the connection status. You'll use this to keep the sketch from starting until the SIM is connected to the network :
Connect to the network by calling
gsmAccess.begin(). It takes the SIM card's PIN as an argument. By placing this inside a
while() loop, you can continually check the status of the connection. When the modem does connect,
gsmAccess() will return
GSM_READY. Use this as a flag to set the
notConnected variable to
false. Once connected, the remainder of
setup will run.
setup with some information to the serial monitor.
Create a function named
readSerial of type
int. You'll use this to iterate through input from the serial monitor, storing the number you wish to send an SMS to, and the message you'll be sending. It should accept a
char array as an argument.
Create a variable to count through the items in the serial buffer, and start a
while loop that will continually execute.
As long as there is serial information available, read the data into a variable named
If the character being read is a newline, terminate the array, clear the serial buffer and exit the function.
If the incoming character is an ASCII character other than a newline or carriage return, add it to the array and increment the index. Close up the
while loops and the function.
loop, create a
char array named
remoteNumber to hold the number you wish to send an SMS to. Invoke the
readSerial function you just created, and pass
remoteNumber as the argument. When
readSerial executes, it will populate
remoteNumber with the number you wish to send the message to.
Create a new
char array named
txtMsg. This will hold the content of your SMS. Pass
readSerial to populate the array.
sms.beginSMS() and pass it
remoteNumber to start sending the message,
sms.print() to send the message, and
sms.endSMS() to complete the process. Print out some diagnostic information and close the
loop. Your message is on its way!
Once your code is uploaded, open the serial monitor. Make sure the serial monitor is set to only send a newline character on return. When prompted to enter the number you wish to call, enter the digits and press return. You'll then be asked to enter your message. Once you've typed that, press return again to send it.