Send SMS from Arduino Uno+Shiel sim900 Quadband

Hi alls

I am trying to send SMS from my shield SIM900 GSM Quadband connected to Arduino Uno without much success so far. The truth is that achieving sending with USB connection from the serial monoitor using the “SendSMS” code given in examples. However, when trying to send without USB connection and connecting the Arduino Uno board to a power 12V 2A, SMS not sent. Then I leave the code I use and link to the website where I got it.

Thank you very much for your attention. I would appreciate very much your help. :wink:

#include <SoftwareSerial.h>
SoftwareSerial SIM900(7, 8);

void setup()
delay(20000); // give time to log on to network.

void SIM900power()
// software equivalent of pressing the GSM shield “power” button
digitalWrite(9, HIGH);
digitalWrite(9, LOW);

void sendSMS()
SIM900.print(“AT+CMGF=1\r”); // AT command to send SMS message
SIM900.println("AT + CMGS = “+654321000"”); // recipient’s mobile number, in international format
SIM900.println(“Hello, world. This is a text message from an Arduino Uno.”); // message to send
SIM900.println((char)26); // End AT command with a ^Z, ASCII code 26
delay(5000); // give module time to send SMS
SIM900power(); // turn off module

void loop()
do {} while (1);

Which shield?

Than you for your reply. You can see the shield in this page:

How have you got the Rx/Tx jumpers set? That shield (TinySine) uses D2 & D3 to communicate.

Then modify your code:

SoftwareSerial SIM900(2, 3);

Thank you danable!!!
I haven´t problem abaut Rx/Tx jumpers, but I modified my code as your recommendation and works.

Thank you very much!!