Why is my fingerprint sensor not responding to my arduino code? - arduino

Question

I have bought a GT-511C1R fingerprint scanner, to work in combination with my Arduino Mega. I used this example: http://www.homautomation.org/2014/10/11/playing-with-finger-print-scanner-fps-on-arduino/
But when i try to blink the led using the default code which came with the library
#include "FPS_GT511C3.h"
#include "SoftwareSerial.h"
// Hardware setup - FPS connected to:
// digital pin 4(arduino rx, fps tx)
// digital pin 5(arduino tx - 560ohm resistor fps tx - 1000ohm resistor - ground)
// this brings the 5v tx line down to about 3.2v so we dont fry our fps
FPS_GT511C3 fps(4, 5);
void setup()
{
Serial.begin(9600);
fps.UseSerialDebug = true; // so you can see the messages in the serial debug screen
fps.Open();
}
void loop()
{
// FPS Blink LED Test
fps.SetLED(true); // turn on the LED inside the fps
delay(1000);
fps.SetLED(false);// turn off the LED inside the fps
delay(1000);
}
it doesn't do anything. On my serial monitor i get:
FPS - Open
FPS - SEND: "55 AA 01 00 00 00 00 00 01 00 01 01"
but the LED of the finger scanner stays off. In combination with my Arduino Uno it does work. What can be the problem?
EDIT: After the answer of changing the pins, it worked just 1 time via pin 10 and 11. After removing the power, it didn't work anymore. Also not on other pins.

Answer 1

Not all pins are supported for SoftwareSerial on the Mega; the RX pin must be an interrupt-on-change pin. The list of such pins:
10, 11, 12, 13, 50, 51, 52, 53, 62, 63, 64, 65, 66, 67, 68, 69
Basically, change the pins in your object to, say, 10 and 11. I would suggest using the hardware serial ports, which the Mega has in abundance, but from my brief perusal, your library seems hardwired to use SoftwareSerial and isn't so easily adapted.