For Loop Counter

int RedLed = 3;
int GreenLed = 4;

void setup() 
{
  int menuChoice;
  pinMode(RedLed, OUTPUT);
  pinMode(GreenLed, OUTPUT);
  
  Serial.begin(9600);
 do
 {
   int menuChoice;
   Serial.println("1. Blinking LEDs ");
   Serial.println("2. LDR");
   //Serial.print("3. ");
   Serial.println("4. Exit");
   while(Serial.available() == 0) {}
   menuChoice = Serial.parseInt();
   
   switch(menuChoice)
     {
     case 1: ledBlink(5,2); break;   
     case 2: LDR(); break;
     }
 }
  while(menuChoice != 4);
  {}
}

void ledBlink(int RedBlink, int GreenBlink)
{
 int i,j,k=1;
 
for(k=1; k=3; k=k+1)
 {
  for(i=1; i<=RedBlink; i++)
  {
    digitalWrite(RedLed, HIGH);
    delay(250);
    digitalWrite(RedLed, LOW);
    delay(250);
   }
   for(j=1; j<=GreenBlink; j++)
   {
    digitalWrite(GreenLed, HIGH);
    delay(250);
    digitalWrite(GreenLed, LOW);
    delay(250);
   }
  } 
}

void loop() {}

Hello,

so far I did a menu and depending on what number you input will call the corresponding function. However the function only runs once, so I decided to implement a for loop so that I could run it as many times as I want.

First I did the for loop like this to run infinitely for(k=1; k<=-1, k++), however the function didn’t even execute.

Secondly when I did the for loop as shown above i.e. for(k=1; k=3; k++) the function runs infinitely, and does not stop after 3 executions.

any tips of what may be going wrong?

Firstly it is very unlikely that a for loop is the answer to your problem.

Secondly

for(k=1; k=3; k++)

is wrong. The expression in the centre tells the for loop when to stop and I expect you meant it to test whether k equals 3, but what you have done is to set k equal to 3.

The ‘=’ is assignment, ‘==’ test for equality, so: for(k = 1; k <= 3; k++) should work.
In the statement for(k=1; k<=-1, k++) middle part is condition and never will be fulfilled.
Use

 for(;;) {
}

for infinity loop.

In short : you must use the double equal sign, when checking for a condition : (if) k==3
When you use the single equal sign, you are assigning the value 3 to K : K = 3.
Thus you are not checking for the K==3 condition.

In your other example, you are using the “less than or equal” <= which is fine, as this is a condition check, because you can not assign a value using <= to a variable.

Our helicopter Bob can not land anymore to get down into such simple explanations :slight_smile:

Anders53:
When you use the single equal sign, you are assigning the value 3 to K : K = 3.
Thus you are not checking for a condition.

Yes, it does. It is checked for zero like this: (k = 3) == 0, which is false in result.

I now understand k=3 is wrong in this case. When I used for(k = 1; k <= 3; k++) it worked as it should, however when I swapped the ‘<=’ with ‘==’, the function just terminated immediately.

The statement for(k=1; k<=-1, k++), is this terminating the loop immediately just because the condition will never be fulfilled ?

Budvar10:
Yes, it does. It is checked for zero like this: (k = 3) == 0, which is false in result.

? :slight_smile:

The statement for(k=1; k<=-1, k++), is this terminating the loop immediately just because the condition will never be fulfilled ?

  1. k = 1; // so k exactly is equal to 1
  2. test k <= -1; // true for -1; -2 …; false for 0, 1…
  3. exit from loop

Did I miss something?

Budvar10:

  1. k = 1; // so k exactly is equal to 1
  2. test k <= -1; // true for -1; -2 …; false for 0, 1…
  3. exit from loop

Did I miss something?

Couldn’t have explained it better. Thanks for all your help guys :slight_smile: Much appreciated

Hi guys i need some help. Here’s my code. I wanna stop the loop counting and show the actual value next to each option.

unsigned long i = 0;
void loop()
{
tft.setCursor(20,80);
tft.setFontScale(1);
tft.setFontSpacing(0);
if (i < 0.01) tft.print(“Not penny: Only quarter”);
tft.setCursor(400,80);
if (i > 0.01 )tft.print(i,DEC);

tft.setCursor(20,120);
tft.setFontScale(1);
tft.setFontSpacing(0);
if (i < 0.05) tft.print(“Not nickel:Only quarter”);
tft.setCursor(400,120);
if (i > 0.05 )tft.print(i,DEC);

tft.setCursor(20,160);
tft.setFontScale(1);
tft.setFontSpacing(0);
if (i < 0.10) tft.print(“Not dime: Only quarter”);
tft.setCursor(400,160);
if (i > 0.25 ) tft.setTextColor(RA8875_WHITE,RA8875_BLACK);
tft.print(i,DEC);
delay(100);
i++;

}

i is declared as an unsigned integer

You increment i by 1 each time through loop evert 100 milliseconds

  if (i < 0.05) tft.print("Not nickel:Only quarter");
  if (i < 0.10) tft.print("Not dime: Only quarter");

How long will its value remain small enough to meet either of the conditions above ?

  if (i > 0.01 )tft.print(i, DEC);
  if (i > 0.05 )tft.print(i, DEC);

How soon will its value always meet the above conditions ?

What is the printing relating to currency all about ?

What is in the rest of your code that you have not posted ?
What has this query got to do with a for loop posed in this thread which is over 2 years old ?

i is an integer. Integers contain the values 0, 1, 2, 3 etc. i starts at 0. First time through that's less than 0.01, 0.05 etc. Then you add 1 to it. Now it's 1 which is greater than all of 0.01, 0.05, 0.10 and 0.25.

I don't know what you're trying to do but I bet that code doesn't do it.

Steve

It’s easier to understand the ‘for’ loop if you understand that is is shorthand for a common form of ‘while’ loop:

for (A; B; C)
  D;

is shorthand for:

A;
while (B) 
  {
  D;
  C;
  }