User Manual

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The next two lines write back a confirmation message to the Serial Monitor.
Serial.print("Turned on LED ");
Serial.println(led);
The first line uses Serial.print rather than Serial.println. The different between the
two is that Serial.print does not start a new line after printing whatever is in its
parameter. We use this in the first line, because we are printing the message in two
parts. Firstly the general bit: 'Turned on LED ' and then the number of the LED.
The number of the LED is held in an 'int' variable rather than being a text string.
Serial.print can take either a text string enclosed in double-quotes, or an 'int' or for
that matter pretty much any type of variable.
After the 'if' statement that handles the case, when a single digit has been handled,
there is a second 'if' statement that checks to see if 'ch' is the letter 'x'.
if (ch == 'x')
{
leds = 0;
updateShiftRegister();
Serial.println("Cleared");
}
If it is, then it clears all the LEDs and sends a confirmation message.