user8787: I am trying to connect my arduino uno to GSM 900A with the help of this tutorial https://elementztechblog.wordpress.com/2014/10/10/interfacing-sim900a-gsm-modem-with-arduino/
but the calling is not being carried out.
The serial output is as following: 
Calling through GSM Modem
Called 
ÿÿÿÿ

and the code is 
#include <SoftwareSerial.h>

SoftwareSerial mySerial(10, 11); // RX, TX

void setup()

{

  Serial.begin(9600);
  Serial.println("Calling through GSM Modem");

  mySerial.begin(9600);
  delay(2000);
  mySerial.println("ATD99abc19965;"); 
  mySerial.println("ATH");
  Serial.println("Called ");
}

void loop() 
{

  if (mySerial.available()) {
    Serial.write(mySerial.read());
  }
}


user8033: You're really missing multiple parts here...
Check out this tutorial: http://tronixstuff.com/2014/01/08/tutorial-arduino-and-sim900-gsm-modules/

First of all, did you power up the SIM900A using its PWRKEY pin?
And can you send and receive AT commands?

How do you know that you have a valid GSM connection?
Did you try AT+CREG? and AT+CPIN?

Do you understand the AT commands you send?

You send ATD (with abc in the number?) and after that you immediately send ATH. Thus you would hang up directly after calling, and probably wouldn't even get to the actual calling part.

#include <SoftwareSerial.h>

SoftwareSerial sim900Serial(10, 11); // RX, TX

void setup()
{
   Serial.begin(9600);
   Serial.println("Calling through GSM Modem");
   sim900Serial.begin(9600);
   delay(2000);
   sim900Serial.println("ATD99abc19965;");
   delay(10000);
   sim900Serial.println("ATH");
   Serial.println("Call ended ");
}

void loop() {
   if (mySerial.available()){
      Serial.write(mySerial.read());
   }
}

Also, your code isn't very well formatted. Compare the code above with yours.

8787: <p>I am trying to connect my arduino uno to GSM 900A with the help of this tutorial <a href="https://elementztechblog.wordpress.com/2014/10/10/interfacing-sim900a-gsm-modem-with-arduino/" rel="nofollow">https://elementztechblog.wordpress.com/2014/10/10/interfacing-sim900a-gsm-modem-with-arduino/</a>
but the calling is not being carried out.</p>

<p>The serial output is as following: </p>

<pre><code>Calling through GSM Modem
Called 
ÿÿÿÿ
</code></pre>

<p>and the code is </p>

<pre><code>#include &lt;SoftwareSerial.h&gt;

SoftwareSerial mySerial(10, 11); // RX, TX

void setup()

{

  Serial.begin(9600);
  Serial.println("Calling through GSM Modem");

  mySerial.begin(9600);
  delay(2000);
  mySerial.println("ATD99abc19965;"); 
  mySerial.println("ATH");
  Serial.println("Called ");
}

void loop() 
{

  if (mySerial.available()) {
    Serial.write(mySerial.read());
  }
}
</code></pre>
 8033: <p>You're really missing multiple parts here...</p>

<p>Check out this tutorial: <a href="http://tronixstuff.com/2014/01/08/tutorial-arduino-and-sim900-gsm-modules/" rel="nofollow">http://tronixstuff.com/2014/01/08/tutorial-arduino-and-sim900-gsm-modules/</a></p>

<ul>
<li><p>First of all, did you power up the SIM900A using its PWRKEY pin?</p></li>
<li><p>And can you send and receive AT commands?</p></li>
</ul>

<p>How do you know that you have a valid GSM connection?
Did you try <code>AT+CREG?</code> and <code>AT+CPIN?</code></p>

<ul>
<li>Do you understand the AT commands you send?</li>
</ul>

<p>You send <code>ATD</code> (with <code>abc</code> in the number?) and after that you <em>immediately</em> send ATH. Thus you would hang up directly after calling, and probably wouldn't even get to the actual calling part.</p>

<hr>

<pre><code>#include &lt;SoftwareSerial.h&gt;

SoftwareSerial sim900Serial(10, 11); // RX, TX

void setup()
{
   Serial.begin(9600);
   Serial.println("Calling through GSM Modem");
   sim900Serial.begin(9600);
   delay(2000);
   sim900Serial.println("ATD99abc19965;");
   delay(10000);
   sim900Serial.println("ATH");
   Serial.println("Call ended ");
}

void loop() {
   if (mySerial.available()){
      Serial.write(mySerial.read());
   }
}
</code></pre>

<p>Also, your code isn't very well formatted. Compare the code above with yours.</p>
