c++ - 'Undefined reference' in Atmel Studio 6.2 -

it's first atmel studio project. i've set ide , made work example code provided new project.

now i'm trying run simple code using pcf8574:

#include <arduino.h> #include <wire.h> #include <pcf8574.h>  /* constants */ const int static serial_speed = 57600;  /* functions */ void setup(); void loop();  /* variables */ pcf8574 expander = pcf8574();  void setup() {     serial.begin(57600);     expander.begin(0x20); }  void loop() {     expander.digitalwrite(1, high);     delay(1000);     expander.digitalwrite(1, low);     delay(1000); } 

but keep getting these errors:

undefined reference 'pcf8574::begin(unsigned char)'   undefined reference 'pcf8574::digitalwrite(unsigned char, unsigned char)' undefined reference 'pcf8574::pcf8574()' 

i've added pcf8574 compiler directory (properties > toolchain > avr c++ compiler > directories) , i'm sure compiler 'sees' .h file - otherwise throw 'no such file or directory' error.

pcf8574 library code: http://nettigo.pl/attachments/196

the same code (copied , pasted) compiled on arduinoide works fine gues it's wrong compiler/linker settings.

has encountered similar problem? don't know else save setup in ide make work fine.