Undefined reference to library error in C++

Question

this code:

#include "SoftwareSerial.h">
#include <avr/io.h>
#include <HardwareSerial.h>
#include <avr/interrupt.h>

void read_response();

int main () {
    sei();
    Serial.begin(2400);
    uint8_t receivePin = 2;
    uint8_t transmitPin = 3;
    SoftwareSerial softSerial(receivePin, transmitPin);
    softSerial.begin(2400);

    while(1){
        softSerial.println("to soft serial");
        Serial.print(softSerial.read());
    }   
}

gives me this error at compile time:

undefined reference to `SoftwareSerial::SoftwareSerial(unsigned char, unsigned char, bool)'

I have tried using #include "SoftSerial.h" but no difference. The SoftSerial.h and SoftSerial.cpp files are in my libraries folder where the HardwareSerial.h files also resides.

What am i missing?

Actually, did you write SoftSerial.cpp yourself? You need to compile it along with your own code. — slugonamission
– slugonamission, Commented Oct 10, 2012 at 14:02
It depends on your environment then. I've not programmed on Arduino so I'm not sure for that specific environment. — slugonamission
– slugonamission, Commented Oct 10, 2012 at 14:04

Philippe Lignon · Accepted Answer · 2012-10-10 14:05:30Z

4

This is not a compile error. This is a linker error.

If SoftSerial is part of your own project, the CPP file is probably not part of the compiled project. If it is an external library, you need to link to it. How you do that depends on your IDE/compiler.

answered Oct 10, 2012 at 14:05

Philippe Lignon

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