user4889: I come to you again because I have a problem with the Arduino SoftwareSerial library. With a basic example I fail to see results in the serial monitor.
The basic code example:
#include <SoftwareSerial.h>
SoftwareSerial mySerial(10, 11);
void setup() {
  mySerial.begin(4800);
}
void loop() {
    mySerial.println("HELLO");
    delay(100);
}

I guess it should show the string "HELLO" on the serial port, but nothing appears. I have found that the baud setting is correct. The hardware is simple. Only an Arduino Uno v3 without any connected component.

user42: If your Arduino is connected via the built-in USB port then you need to use the hardware serial port (pins 0 and 1). To do that, call Serial.begin(..) and Serial.println(..), instead of mySerial....
SoftwareSerial is used when you want to connect via serial on some other pins. It allows your program to emulate serial input/output in software instead of relying on dedicated hardware. In this case, your program is trying to setup software serial on pins 10 and 11. That won't show up on the serial monitor because it's not connected to those pins.

user3866: Addition to Peter R. Blommfield
What is your problem?
Connect your device, run this sketch and you are good to go :)
/* TEST */
#include <SoftwareSerial.h>

/* Connect device Rx - 10, Tx - 11 */
SoftwareSerial mySerial(10, 11);


void setup() {
  Serial.begin(9600);   // This will communicate with PC via USB
  mySerial.begin(4800); // This will communicate with device via 10,11 pins with 4800 baud rate
}
void loop() {
    Serial.println("HELLO");   // Sends string to PC to Serial Monitor
    mySerial.println("HELLO"); // Sends string to device
    delay(100);                // Waits here 100ms and then goes on
}


4889: 

<p>I come to you again because I have a problem with the Arduino SoftwareSerial library. With a basic example I fail to see results in the serial monitor.</p>

<p>The basic code example:</p>

<pre class="lang-C++ prettyprint-override"><code>#include &lt;SoftwareSerial.h&gt;
SoftwareSerial mySerial(10, 11);
void setup() {
  mySerial.begin(4800);
}
void loop() {
    mySerial.println("HELLO");
    delay(100);
}
</code></pre>

<p>I guess it should show the string "HELLO" on the serial port, but nothing appears. I have found that the baud setting is correct. The hardware is simple. Only an Arduino Uno v3 without any connected component.</p>
 42: <p>If your Arduino is connected via the built-in USB port then you need to use the hardware serial port (pins 0 and 1). To do that, call <code>Serial.begin(..)</code> and <code>Serial.println(..)</code>, instead of <code>mySerial...</code>.</p>

<p><code>SoftwareSerial</code> is used when you want to connect via serial on some other pins. It allows your program to emulate serial input/output in software instead of relying on dedicated hardware. In this case, your program is trying to setup software serial on pins 10 and 11. That won't show up on the serial monitor because it's not connected to those pins.</p>
 3866: <p>Addition to <code>Peter R. Blommfield</code></p>

<p>What is your problem?</p>

<p>Connect your device, run this sketch and you are good to go :)</p>

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

/* Connect device Rx - 10, Tx - 11 */
SoftwareSerial mySerial(10, 11);


void setup() {
  Serial.begin(9600);   // This will communicate with PC via USB
  mySerial.begin(4800); // This will communicate with device via 10,11 pins with 4800 baud rate
}
void loop() {
    Serial.println("HELLO");   // Sends string to PC to Serial Monitor
    mySerial.println("HELLO"); // Sends string to device
    delay(100);                // Waits here 100ms and then goes on
}
</code></pre>
