Go Down

Topic: Unable to use pass HardwareSerial to classes in due (Read 2662 times) previous topic - next topic


I have a Due that is using a gps and I am trying to build a library to simplify its use. I actually am going to reuse the code on a couple of Dues so I want to be able to pass a specific serial port to use for communication so I can change it based on what pins I use. For now I have a simple class set up that accepts a HardwareSerial pointer in the constructor and a function to print a test message. The code compiles fine and on a Uno it actually works as expected. When I compile it for the Due I get the following warning.

sketch_jan14a.cpp.o: In function `SerialTest::begin(long)':
C:\Users\pepi0003\Downloads\arduino-1.5.1r2/sketch_jan14a.ino:29: warning: undefined reference to `HardwareSerial::begin(unsigned long)'
Binary sketch size: 9,720 bytes (of a 524,288 byte maximum)

The code still compiles and can be uploaded to the due but doesn't actually print anything on the serial port. Here is the code I am using. Any help would be appreciated.

Code: [Select]
class SerialTest{
    SerialTest(HardwareSerial *ser);
    void begin(long baud);
    void printHelloWorld();
    HardwareSerial *hwSerial;   

SerialTest test(&Serial);

void setup(){

void loop(){

SerialTest::SerialTest(HardwareSerial *ser){
  hwSerial = ser;

void SerialTest::begin(long baud){

void SerialTest::printHelloWorld(){
  hwSerial->println("Hello world!");


Jan 15, 2013, 02:20 am Last Edit: Jan 15, 2013, 01:34 pm by drobe011 Reason: 1
Not sure if this helps, but here is how I have done it in my endeavours:

I originally tried to use HardwareSerial Class to pass, but seems it wasn't the right object.  In the compiler error output it complained about trying to convert UARTClass to HardwareSerial.  Once I dug around a few, I found the actual two classes I needed to be able to pass a HardwareSerial object.


Code: [Select]
UARTClass *ucTx;
ucTx = &Serial;


Code: [Select]
USARTClass *ucTx;
ucTx = &Serial1; // Can be Serial 1-3 [s]Could just use Serial for HardwareSerial0[/s]


Edit: USARTClass is for HardwareSerial1-3(Serial1-Serial3).
HardwareSerial0(Serial) is of class UARTClass (virtual COM port via ATmega16U2 to PC).

main.cpp includes Arduino.h
Arduino.h includes HardwareSerial.h and variant.h
variant.h includes both UARTClass.h and USARTClass.h


Jan 15, 2013, 02:50 am Last Edit: Jan 15, 2013, 03:00 am by lloyddean Reason: 1
Code: [Select]

class SerialDevice
   HardwareSerial&     _serial;

   SerialDevice(HardwareSerial& serial)
       : _serial(serial)

   void begin(long baud)   { _serial.begin(baud);             }
   void printHelloWorld()  { _serial.println("Hello world!"); }

SerialDevice device(Serial);

void loop()

void setup()


Where does your class learn what the HardwareSerial name refers to? You appear to missing some necessary include statements.


I tried your code Dave and it is working perfectly now. I had been poking around in the old libraries and didn't realized that the ones for the due where stored in a separate folder. Is there any drawback to passing a reference to the class like in lloydeans code as apposed to using a pointer.


I believe in the context above pointer/reference would equal to the same thing.

The goal I was trying to achieve passing by pointer or reference was to eliminate passing by value, ie. sending the whole USARTClass object as a function param.  Save more memory just passing reference or actual memory location to USARTClass versus a (basically) literal copy of it.



If by reference as above the compiler will never allow you to compile without passing the Serial device.

Code: [Select]

SerialDevice device;

Will generate a compile time error/warning


Feb 10, 2014, 12:54 am Last Edit: Feb 10, 2014, 09:39 am by ahkub Reason: 1
Hello brickmaster32000,
I'm fighting the same issue on a Due as you did.
You said, when implementing Dave's workaround, it works for you.
I have a hard time figuring out where exactly you needed to place Dave's code.
May I ask you to post your code with Dave's workaround included?
Much appreciated.

Best regards,

Sorry for the dumb question. I looked at your code at GitHub (Century-Fablab-Projects) and found the answer:
I need to replace all "HardwareSerial" with "USARTClass" in the CPP file as well as in the H file.
Best regards,

Go Up