How to call a void function within if statement (Arduino) - c++

Question

I wrote a code supposed to do the following: if I press one button while in loop void btnpress(), the program is sent to another function void blink2(), and then one led goes on and after 3 secs the led should go off, and it should also return to void btnpress() again via btnpress();.
The issue is that if i press the button and release, the led goes on and stay still infinitely on, program seems not to execute the following last parts digitalWrite(LED_BUILTIN, LOW); and btnpress();.
const int btnpin = 9;
int btnstate = 0;
unsigned long currentTime;
unsigned long previousTime;
const long period = 3000;
// the setup
void setup()
{
pinMode(LED_BUILTIN, OUTPUT);
pinMode(btnpin, INPUT);
Serial.begin(9600);
}
// the loop
void loop()
{
btnpress();
}
void btnpress()
{
Serial.println("Press button");
delay(500);
btnstate = digitalRead(btnpin);
if (btnstate == HIGH) {
previousTime = millis();
blink2();
}
}
void blink2()
{
if (currentTime - previousTime >= period) {
Serial.println("Led on");
previousTime = currentTime;
digitalWrite(LED_BUILTIN, HIGH); // turn the LED on
}
else {
Serial.println("Led off");
digitalWrite(LED_BUILTIN, LOW);
btnpress();
}
}

Answer 1

if I press one button while in loop void btnpress(), the program is
sent to another function void blink2(), and then one led goes on and
after 3 secs the led should go off, and it should also return to void
btnpress() again via btnpress();
According to this statement, I can suggest you to use the following code just to be sure if your functions are working according to your reqirement.
const int btnpin = 9;
int btnstate = 0;
//unsigned long currentTime;
//unsigned long previousTime;
const long period = 3000;
// the setup
void setup()
{
pinMode(LED_BUILTIN, OUTPUT);
pinMode(btnpin, INPUT);
Serial.begin(9600);
}
// the loop
void loop()
{
btnpress();
}
void btnpress()
{
Serial.println("Press button");
delay(500);
btnstate = digitalRead(btnpin);
if (btnstate == HIGH) {
// previousTime = millis();
blink2();
}
}
void blink2()
{
Serial.println("Led on");
digitalWrite(LED_BUILTIN, HIGH);
delay(3000);
Serial.println("Led off");
digitalWrite(LED_BUILTIN, LOW);
//btnpress(); It's already inside the Void loop
}
If it's working well then function call is okay.
And there has no issue with "How to call a void function within if statement (Arduino)"
The problem may be inside your if statement,
if (currentTime - previousTime >= period) {
Serial.println("Led on");
previousTime = currentTime;
digitalWrite(LED_BUILTIN, HIGH); // turn the LED on
}
here, the currentTime is not Defined.