PWM delay without blocking the code

Question

I want my LED to turn on gradually without using the delay() function and blocking the code.

Here's the code i came up with:

int led_pin = 6;
unsigned long millisTimer = 0;
int PWMdelay = 5000;
int condition = 0;
int i = 0;
void setup() {
 pinMode(led_pin, OUTPUT);
}
void loop() {
 if(condition == 1){
 if ((millis() - millisTimer) > PWMdelay){
 if(i<255){
 i++;
 millisTimer = millis();
 }
 }
 analogWrite(led_pin, i);
 }
}

Is this the "right way" of slowing the PMW duration from 0 to 255 or there are alternative/better/easier ways?

• chrisl: Seems ok for fade in timer. Why are you doing the else with i--? Do you want to fade out the LED after the fade in? That does not work this way, since it will only vary between 254 and 255.
• Juraj: the Fade example in IDE uses delay, but shows how to go up and then down. and put millisTimer = millis(); outside if-else
• Sim Son: From my personal definition, the "right way" is a way that works. So, does it work? Your approach is a common way to do tasks without delay (like in the BlinkWithoutDelay example)
• Juraj: see the Fade example and the BlinkWithoutDelay example in IDE Examples menu
• Sim Son: That's fine, I do it the same way

Answer 1

Here is my take at this - I've followed the example code mentioned by other members and here is "FadeWithoutDelay"

const int ledPin = 11;
unsigned long previousMillis = 0; // will store last time LED was updated
const long interval = 100; // fade interval (milliseconds)
int brightness = 0; // how bright the LED is
int fadeAmount = 5; // how many points to fade the LED by
void setup() 
{
 pinMode(ledPin, OUTPUT); // set the digital pin as output:
}
void loop() 
{
 unsigned long currentMillis = millis();
 if (currentMillis - previousMillis >= interval) 
 {
 previousMillis = currentMillis; // save the last state
 analogWrite(ledPin, brightness); // Set the brightness
 brightness = brightness + fadeAmount; // change the brightness for next time through the loop
 // reverse the direction of the fading at the ends of the fade:
 if (brightness <= 0 || brightness >= 255) 
 {
 fadeAmount = -fadeAmount;
 }
 }
}