GMU:Functions and Classes (Arduino)

Motivation

Soon after starting to write the program for your robot you will encounter some typical problems:

• clarity: the bigger the program gets the harder it is to keep the general overview
• decoupling: you only want to change a certain part of the program without influencing all the rest
• recyclability: there are several similar parts in your robot for which you would like to reuse particular sections of your code

These problems reach back to the beginning of programming and their solution is an art and a science at the same time. It generally helps a lot to separate your program into single subunits that are relatively independent from each other.

Example: Controlling Motors

The function is an enormous useful tool that can help you structuring your code. Functions allow you to sum up several operations under the same command. This command can be called again and again without knowing about or duplicating the included code.

Here is an example for a function for setting the speed of a motor that is connected to an H-bridge:

void setMotorSpeed(int newSpeed, int forwardPin, int reversePin, int throttlePin){ // should it spin forwards or backwards? if(newSpeed>0){ //spin forwards digitalWrite(reversePin,LOW); digitalWrite(forwardPin,HIGH); }else{ //spin backwards digitalWrite(forwardPin,LOW); digitalWrite(reversePin,HIGH); } //adjust the speed: analogWrite(throttlePin, newSpeed); }

Now (and for every prospective motor movement) we only need to write one single line in order to for instance setting the left wheels speed:

setMotorSpeed(speed, leftForwardPin, leftReversePin, leftThrottlePin); // the pin numbers are saved in variables

This already saves us a lot of typing – But one thing still seems quite laborious: we have to know the exact pin numbers every time we want to change the speed.

Imagine a program in which similar function calls are distributed all over. In case of a hardware update you would have to find every single function call and change the parameters manually. This effort could surely be spent for more useful things..

It would be ideal to find a way of calling a certain function that only offers the most useful parameters (like setting the speed) and which handles technical details (switching pins on and off) internally.