I was wondering the correct method to construct objects for use in the setup and loop scopes. I tried working constructing in the global scope, but I get garbage values printed to serial (probably from misusing pointers)? If I use the new keyword, then it works, but I heard that that is not best practice.

I is there a better way I should do this?

// navigator.cpp

#include "navigator.h"

Navigator::begin(Waypoint* w, int count) {
  waypoints = w; 
  pointCount = count;
  next = 0;                               // start with first waypoint
  course = 90;                          // Notice that initial course is due East



// navigator.h 

#define _navigator_h

#if defined(ARDUINO) && ARDUINO >= 100
  #include "Arduino.h"
  #include "WProgram.h"

struct Waypoint {
  double lat, lon;

class Navigator {
  begin(Waypoint* w, int);



// TransAt.ino

#include "navigator.h"

Waypoint w = { 43.36, -75.1 };  // These objects must be accessible in both setup() and loop(), but we can't use the new keyword
Navigator nav();                    // That means we have to do a lot of the heavy lifting here

uint32_t timer = millis();

void setup() {
  nav.begin(&w, 1); 

void loop() 

  • 2
    No Serial.begin(baudrate);? Also Navigator nav(); is kind of function prototype. You can use Navigator nav; – KIIV Jan 20 '18 at 16:10
  • What might be easy in such cases, is first to make it in e.g. VisualStudio (without using Arduino), and later when everything works on a PC (where you can debug everything easily) run it on an Arduino. Only calls like Serial, you have to comment out or stub. – Michel Keijzers Jan 20 '18 at 16:12
  • 1
    Debugging questions need to include the actual output produced. Is it repeatable or random? also, you should reduce your code to a minimum example which demonstrates the problem, and correct your title for the fact that there is no such thing as an ATmega2056. Are you targeting the bare chip, or an Arduino Mega2560/clone? – Chris Stratton Jan 20 '18 at 17:40

I tried working constructing in the global scope, but I get garbage values printed to serial ...

Constructors in global scope are called before init and setup and thus are probably executing too soon for you. This would account for the garbage printed to serial, because your constructor is printing before the Serial.begin() call.

You can put constructors in global scope, however they should do fairly trivial things (eg. setting a counter to zero, or a pointer to NULL). Do not rely upon the system being initialized, thus do not call functions like millis, nor should you be using dynamic memory allocation at this point.

Most classes defer their "real" initialization to a begin function (eg. Serial.begin) because it is safe to do that, usually in the setup function.

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