Arduino command timeout - arduino

Question

I'm currently working with a Arduino to forfill one of my DIY projects.
As it currently stands, I have my fingerprint scanner (GT-511C3) connected to my Arduino and that works great. I'm able to verify enrolled fingerprints.
The verifying of the finterprints happends via Raspberry Pi command (whom is initiated by a button press)
Logically, this means, when the button is pressed, the Raspberry Pi sends a 'validate' command to the Arduino, whom in return ask the Fingerprint scanner to run the validate command.
However, I would like to have a timeout after the validate command it sent. The timeout needs to make sure that if the button pressed (and the validate command is initated) but no one puts their finger on the machine it timeouts and reverts back to a state where it waits for the validate command.
I'm not able to complete this. This is the code I've tried:
#include "FPS_GT511C3.h"
#include "SoftwareSerial.h"
FPS_GT511C3 fps(4, 5);
int val = 0;
void setup()
{
Serial.begin(9600);
delay(100);
fps.Open();
fps.SetLED(false);
}
void loop(){
if (Serial.available() > 0) {
Continue:
if(Serial.find("validate")){
fps.SetLED(true);
do {
++val;
delay(100);
}
while(fps.IsPressFinger() == false || val > 150);
if(val <= 150){
fps.SetLED(false);
goto Continue;
}
if (fps.IsPressFinger()){
fps.CaptureFinger(false);
int id = fps.Identify1_N();
if (id <200)
{
Serial.print("Verified ID:");
Serial.println(id);
fps.SetLED(false);
}
else
{
Serial.println("Finger not found");
fps.SetLED(false);
}
}
else
{
Serial.println("Please press finger");
}
delay(100);
}
}
}
The code otherwise works fine, if the finger is placed and validated, it turns off and goes back to waiting for another validate command.
Any help would be greatly appreciated!

Answer 1

First, get rid of the label and goto. There is no justification for it here; it's considered bad programming practice and shouldn't be used unless you know exactly what you're doing. Only in Assembly is it okay to use goto (equivalent to JMPs) liberally.
Next, your while condition is wrong. If you try to interpret it, you'll notice it doesn't make any sense:
Wait for as long as nobody has placed a finger or if the timeout has expired.
What you probably want is:
Wait for as long as nobody has placed a finger and the timeout has not expired.
which translates to:
while(fps.IsPressFinger() == false && val < 150);
The IF condition that follows, is also wrong and should mean:
if the timeout has expired
translating to:
if(val >= 150){
fps.SetLED(false);
val = 0;
continue;
}
Notice the use of the continue keyword which restarts a loop. To make it legit, change if (Serial.available() > 0) to while (Serial.available() > 0).