Arduino Forum > Products > Arduino GSM Shield > About the SIM900A module Alerts

Hello

I am using Arduno UNO with a GSM module (SIM900A). The module is powered by the 5V outputs of the UNO. The 5RX and 5TX pins are connected to pins 11 and 9 of the Arduino UNO board, I used the SoftwareSerial.h library. My code works fine I managed to send and receive my messages from the Arduino board without any problem.
But when I power with an external power supply nothing gives more when I use another aptops to power nothing gives the device only works when connected to my machine. Please, I need help. I am running out of ideas.

#include <SoftwareSerial.h>
SoftwareSerial mySerial(9, 11); // RX | TX
int Chambre1 = 7;
int strCumul
void setup()
{
SIM900A.begin(9600); // opens serial port, sets data rate to 9600 bps
pinMode(Chambre1, OUTPUT);
SIM900A.println("AT+CNMI=2,2,0,0,0"); // Commande AT pour recevoir un SMS en direct
SIM900A.println("AT+CMGF=1"); //Définit le module GSM en mode texte
strCumul = "";

}
void loop()
{
if (SIM900A.available()>0)
{
// Serial.println (strCumul.indexOf("ledOn")); // teste de la valeur retourner
strCumul.concat(char(SIM900A.read())); //Lire et cumuler les caract
delay(100);

// allumer la la chambre 1
if ((strCumul.indexOf("CH1_ON")>0))
{
SIM900A.println("AT+CMGF=1"); //Définit le module GSM en mode texte
delay(1000); // Delay of 1000 milli seconds or 1 second
SIM900A.println("AT+CMGS="+237696414636"\r"); // numéro
delay(1000);
SIM900A.println(Msg);//Le texte SMS que vous voulez envoyer
delay(100);
SIM900A.println((char)26);// Code ASCII de CTRL + Z
delay(1000);

digitalWrite(Chambre1,HIGH);
SIM900A.println("AT+CMGD=1,4"); // effacer le SMS de la Carte SIM
strCumul = "";
}
}
}