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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 Arduino provide (and extend) the utility of using subroutines (GOSUB in BASIC).
Standardizing code fragments into functions has several advantages:
There are two required functions in an Arduino sketch, setup() and 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.
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; }
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; 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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This reference is licensed under a Creative Commons Attribution-ShareAlike 3.0 License and is based on the Arduino reference. Code samples in the reference are released into the public domain.