could not find what this code actually mean

Using Arduino Programming Questions
#1

please anyone help me understanding each line of this code.
this code is a part of arduino mppt solar charge controller

void perturb(boolean init=false)
{
  static byte pulseWidth = 0;
  static boolean trackDirection = false; //counts down / pwm increases
  // static int loopCounter = 0;
  if (init) 
  {
    pulseWidth = 255;
    trackDirection = false;
  }
  else 
  {
    if (!trackDirection) 
    {
      if (pulseWidth != 0)
      {
        pulseWidth--;
      } 
      else
      {
        trackDirection = true;
      }
    }
    else 
    {
      if (pulseWidth != 255) 
      {
        pulseWidth++;
      }
      else
      {
        trackDirection = false;
      }
    }
  }
  pwmWrite(3, pulseWidth); //write perturbed PWM value to PWM hardware
  if ((panelWatts - lastPanelWatts) < -0.1) 
  trackDirection = !trackDirection;
}
  • In the first line boolean init is assigned a value. the there is a if statement with test condition initif(init) How and when this loop is executed?[/li]
#2

if(init)

is shorthand for

if(init == HIGH)

or

if(init == true)

Leo..

#3

To help you understand something, we must first explore what it is you don't understand.

void perturb(boolean init=false)
{

This defines a void function, taking one boolean argument called "init", which is defaulted to false.
So, if you call perturb with no argument, the compiler will provide a default argument.

#4

Wawa:
if(init)

is shorthand for

if(init == HIGH)

or

if(init == true)

Leo..

I would say it is shorthand for "if (init != 0)".

#5

I would say it is shorthand for "if (init != 0)".

This is correct; but, general survey has revealed that if(init) stands for:if(init == HIGH)

#6

GolamMostafa:
This is correct; but, general survey has revealed that if(init) stands for:if(init == HIGH)

"general survey "?

Reference/link please

HIGH is an Arduino-defined macro - it is foolish to suggest it has some special meaning in the language.

#7

Wawa:
if(init)

is shorthand for

if(init == HIGH)

or

if(init == true)

Leo..

Thank you :slight_smile:

#8

A ‘boolean’ variable, like ‘init’, can contain either ‘false’ (0) or ‘true’ (1). Other data types, when used in a boolean expression like in an ‘if’ or ‘while’, evaluate to ‘false’ if they are 0 and ‘true’ if they are not 0. The constant ‘false’ is defined to be 0 and the constant ‘true’ is defined to be 1. In the Arduino libraries, HIGH is defined as 1 and LOW is defined as 0. It is safe to compare against 0/false/LOW in a boolean expression but not safe to compare against 1/true/HIGH since 1 is not the only value that evaluates to ‘true’. For example:

    int variable = 10;
    if (variable)  This executes because variable is != 0
    if (variable != false) This executes because variable is != 0
    if (variable == true) This DOES NOT execute because 10 != 1
#9

GolamMostafa:
This is correct; but, general survey has revealed that if(init) stands for:if(init == HIGH)

Still waiting for the link or reference.

#10

OP: the function is defined with a default argument. If you explicitly pass an agrgument like peterub(true), then the if will get executed.

Everyone else: the init parameter does not appear to intended to be the result of a digital read. It appears to be intended to be used something like so:

void setup() {
  peturb(true); // initial perturbation
}

loop() {
  peturb();
}

Since LOW is usually defined to be 0, and HIGH to be 1, yes you can usually use if(digitalRead(fooPin)) and it will work. But you shouldn't.

#11