Functions

Segmenting code into functions allows a programmer to create modular pieces of code that perform a defined task and then return to the area of code from which the function was “called”. The typical case for creating a function is when one needs to perform the same action multiple times in a program.

For programmers accustomed to using BASIC, functions in 86Duino provide (and extend) the utility of using subroutines (GOSUB in BASIC).

Standardizing code fragments into functions has several advantages:

• Functions help the programmer stay organized. Often this helps to conceptualize the program.
• Functions codify one action in one place so that the function only has to be thought out and debugged once.
• This also reduces chances for errors in modification, if the code needs to be changed.
• Functions make the whole sketch smaller and more compact because sections of code are reused many times.
• They make it easier to reuse code in other programs by making it more modular, and as a nice side effect, using functions also often makes the code more readable.

There are two required functions in an 86Duino sketch, setup() と loop(). Other functions must be created outside the brackets of those two functions. As an example, we will create a simple function to multiply two numbers.

事例

To “call” our simple multiply function, we pass it parameters of the datatype that it is expecting:

void loop{
  int i = 2;
  int j = 3;
  int k;
 
  k = myMultiplyFunction(i, j); // k now contains 6
}

Our function needs to be declared outside any other function, so “myMultiplyFunction()” can go either above or below the “loop()” function.

The entire sketch would then look like this:

void setup(){
  Serial.begin(9600);
}
 
void loop() {
  int i = 2;
  int j = 3;
  int k;
 
  k = myMultiplyFunction(i, j); // k now contains 6
  Serial.println(k);
  delay(500);
}
 
int myMultiplyFunction(int x, int y){
  int result;
  result = x * y;
  return result;
}

Another example

This function will read a sensor five times with analogRead() and calculate the average of five readings. It then scales the data to 8 bits (0-255), and inverts it, returning the inverted result.

int ReadSens_and_Condition(){
  int i;
  int sval = 0;
 
  for (i = 0; i < 5; i++){
    sval = sval + analogRead(0);    // sensor on analog pin 0
  }
 
  sval = sval / 5;    // average
  sval = sval / 4;    // scale to 8 bits (0 - 255)
  sval = 255 - sval;  // invert output
  return sval;
}

To call our function we just assign it to a variable.

int sens;
 
sens = ReadSens_and_Condition();

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86Duino のリファレンスのテキストは Arduino レファレンス を編集したもので、 Creative Commons Attribution-ShareAlike 3.0 License下でライセンスされています。リファレンス内のコードサンプルはパブリックドメインとして公開されています。