Non-blocking delay not looping in switch() case

Projects Programming
1

Hi, I'm using non-blocking delay in a switch() case and the delay is not looping?

In the example below I would expect the serial monitor to switch between YES / NO every 5000 milliseconds. But it just switches from YES to NO once. Do I need a while statement of have I made a mistake in the code?

The switch(newPos) case is selected using a rotary encoder.

void loop() {
  
  // State machine
  preset();

  // delay between changing presets
  delay(10);

}  // loop

void preset() {

  unsigned long previousMillis = 0;
  const long interval = 5000;

  // State machine
  switch (newPos) {

    case 1:
        // Preset 1
        // ...
        break;

    case 2: {
        // Preset 2
        unsigned long currentMillis = millis();

        if (currentMillis - previousMillis >= interval) {
          previousMillis = currentMillis;
          Serial.println("YES");
        } else {
          Serial.println("NO");
        }

      }
      break;
  } // state machine

} // preset
2

Well there's your problem.

/Users/john/Documents/Arduino/sketch_oct12a/sketch_oct12a.ino: In function 'void preset()':
sketch_oct12a:16:11: error: 'newPos' was not declared in this scope
   switch (newPos)
           ^~~~~~
exit status 1
'newPos' was not declared in this scope
3

I added some to get it to compile. As I did I noticed that your 'previousMillis' veriable is not static or global so it gets set to 0 each time you enter preset().

4

Hi John,

Excellent, thanks.

The 'unsigned' previousMillis seems to be the issue. I changed it to 'static' and inserted the Blink Without Delay code to test and the LED flashes when I select the switch(newPos) case using the rotary encoder.

I'm controlling a DC motor so what I've done for the moment is to insert the start / stop commands in the 'blink' code. What would be the more elegant way of doing this and removing the LED from the circuit?

// if the LED is off turn it on and vice-versa:
if (ledState == LOW) {
  ledState = HIGH;
  myMotor->run(FORWARD);
  myMotor->setSpeed(blower * newPos);
} else {
  ledState = LOW;
  myMotor->run(RELEASE);
}

// set the LED with the ledState of the variable:
digitalWrite(ledPin, ledState);
5

... actually having the LED in the circuit will be useful as I'm creating a random delay and the visual feedback will be valuable.