Hello everyone. I'm just wondering if this can be done and if yes, where can I find an example. I've tried a millis form and a for loop with no luck.
I can fade an LED in and out using either method. What I am trying to achieve is this;
Led one fades in, when it reaches max pwm (brightness), a second LED fades in while the first LED fades out.
Any help appreciated.
Quite possible using for loops if you don't mind blocking code
Quite possible using millis() timing if you want non blocking code. Let loop() do what it is best at
What have you tried ?
Sounds simple enough.
Please show your best effort and describe what it does and what you would like it to do instead.
A for loop is really just a while loop with initialization. It's not that hard to translate into a state machine.
I know it sounds simple to you all but I'm sitting here looking at this:
for (int i = 0; i < 255; i++) { //if i is less than 255 then increase i with 1
analogWrite(pwmLED, i); //write the i value
delay(20); //wait 5 ms then loop again
}
for (int i = 255; i > 0; i--) { //descrease i with 1
analogWrite(pwmLED, i);
delay(5);
analogWrite(pwmLED, LOW);
}
and this, with no idea where to start
const byte pwmLED = 5;
#define UP 0
#define DOWN 1
const int minPWM = 0; // constants for min and max PWM
const int maxPWM = 255;
byte fadeDirection = UP; // Fade Direction
int fadeValue = 0;
byte fadeIncrement = 5; // How smooth to fade?
unsigned long previousFadeMillis; // timing Variable,
unsigned long previousHighMillis; //How long to stay high
int fadeInterval = 45; // increment?
int highInterval = 2000;
void setup() {
analogWrite(pwmLED, fadeValue);
}
void doTheFade(unsigned long thisMillis) {
if (thisMillis - previousFadeMillis >= fadeInterval) {
if (fadeDirection == UP) {
fadeValue = fadeValue + fadeIncrement;
if (fadeValue >= maxPWM) {
fadeValue = maxPWM; // At max, limit and change direction
if (fadeValue = maxPWM) {
digitalWrite(pwmLED, HIGH); }
if(thisMillis - previousHighMillis <= highInterval) { }
fadeDirection = DOWN;
}
} else {
//if we aren't going up, we're going down
fadeValue = fadeValue - fadeIncrement;
if (fadeValue <= minPWM) {
// At min, limit and change direction
fadeValue = minPWM;
digitalWrite(pwmLED, LOW);
fadeDirection = UP;
}
}
analogWrite(pwmLED, fadeValue); // update when it changes
// reset
}
}
void loop() {
unsigned long currentMillis = millis();
doTheFade(currentMillis);
}
Here is how you implement a for loop using a state machine:
for(i=3; i<6; i++) {<somecode>}
decomposes as the sequence
i=3;
while (i<6) {
<somecode>
i++;
}
For the state machine you would do something like
if (state == INITIALIZE) {
i=3;
state = RUN;
}
else if (state == RUN and i<6) {
<somecode>
i++;
}
else {
state = IDLE;
}
To activate it, you just assert:
state = INITIALIZE;
Thanks aarg 
For me, state machines are almost always easier to read, understand and maintain using switch/case
switch (state)
{
INITIALIZE:
i = 3;
state = RUN;
break;
RUN:
if (i < 6)
{
<somecode>
i++;
}
else
{
state = IDLE;
}
break;
}
But like a lot of things it is a matter of one's own preferences
Polliwog:
Led one fades in, when it reaches max pwm (brightness), a second LED fades in while the first LED fades out.
If you mean that one LED should be bright when the other is dark then something simple like this should do the trick
void loop() {
static byte ledAval = 0;
static byte ledAchange = 10;
byte ledBval = 255 - ledAval;
digitalWrite(ledApin, ledAval);
digitalWrite(ledBpin, ledBval);
// check are we going to exceed the limits
if ((ledAval + ledAchange ) < 0 or (ledAval + ledAchange) > 255) {
ledaAchange = - ledAchange;
}
ledAval += ledAchange;
delay(50);
}
...R