Ho i can fight with many IF condition?

Using Arduino Programming Questions
#1

Hello!

In my project i have some input data, variable from 0 to 360 (compass)
And i need set servo position depending of input data.
Trouble is - to many IF condition in code.
I have table
Compass Servo
(0 to 10) and (350 to 0) 20
(11 to 20) and (349 to 340) 22
etc

And in program - this is big quality of IF condition. Working slow :frowning:

May be exist some elegant way to obtain many IF checking in code?

Thanks.
Sorry my bad English

#2

You might try the switch case with the gcc ... extension.

You could create a lookup table with 360 entries and put the servo step there:

byte servo_pos[360] = {
20,20,20,20,20,20,....22,22,22,22....20,20};

#3

You can either use a bunch of if statements, or you can use math. Look at your input and output values there and see if you notice a pattern.

#4 
if((compass > 10 && compass <= 20) || (compass < 350 && compass >= 340))
  {
    Servo = 22; //whatever your servo code is
  }
else if (compass <= 10 || compass >=350)
  {
     Servo = 20; //again, your code
   }
else
   {
     //whatever you need it do when the compass reads 21-339
   }

Post your code so we can help analyze.

#5

Another way is to use a switch/case, which I think is easier to read:

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);

}

void loop() {
  // put your main code here, to run repeatedly:
  char buffer[5];
  int charsRead;
  int number;
  int servo;

  if (Serial.available() > 0) {
    charsRead = Serial.readBytesUntil('\n', buffer, sizeof(buffer) - 1);  // Leave room for null
    buffer[charsRead] = '\0';    // Now it's a string
    number = atoi(buffer);

    Serial.print("Number is: ");
    Serial.println(number);
    if (number >= 0 || number < 360) {


      switch (number) {
        case 0 ... 10:
        case 350 ... 359:
          servo = 20;
          break;
        case 11 ... 20:
        case 340 ... 349:
          servo = 22;
          break;

        // More similar cases

        default:
          Serial.println("Should ever see this.");
          servo = -1;
          break;
      }
      Serial.print("Servo = ");
      Serial.println(servo);
    }
  }

}

Note that you need to insert a space before and after the ellipsis operator (i.e., … )for it to work.

Edit: Sorry, Keith…didn’t see your post in time.

#6

Also, note that this is not standard C, but a gcc extension, which is fine if this is only going to be used on the arduino.

#7

Also as you are treating opposite compass readings as equivalent (for instance 5 and 355 should produce the same servo position) you can easily eliminate half of the if-then checks using

if(compassReading>180)
{
compassReading = 360 - compassReading;
}

Meaning in this example 360-355 = 5

Meaning your range will always be 0-180.

#8

If you have a series of tests do them from one end to the other and it will be much simpler

if (angle > 350) {
   servoPos = 20;
}
else if (angle > 340) {
   servoPos = 22;
}
else if (angle > 

etc etc

However, I wonder what happens if you subtract 180 from the angle and take the abs value (because the upper and lower half seem to be the same) and then divide by 8 and add the answer to 20 - allways using integer arithmetic.

servoPos = abs(angle - 180) / 8 + 20;

...R

#9