LCD Pick 18F46K20 (OLED)

[joosthuis21]

I'm programming in HI-TECH the pic controller 18F46K20, but I have problems programming the LCD screen OLED. I got the following error:
""undefined symbols _oled_putc_2x"", but I have the same symbols in the oled.h file so why is this error.

This is the code:

#include <htc.h>
#include <18f46k20.h>
#include "oled_interface.h"
#include "oled.h"

unsigned char hello[7];
unsigned char world[7];
unsigned int delay;

void InterruptHandler(void);
void InitializeSystem(void);

void main(void){

char temp;

InitializeSystem();

_delay(50000);
while(delay--);

oled_init();
oled_clear();
oled_refresh();

oled_putc_2x('\n');
oled_putc_2x('\t');
oled_putc_2x('\t');


oled_putc_2x('H');
oled_putc_2x('e');
oled_putc_2x('l');
oled_putc_2x('l');
oled_putc_2x('o');

oled_putc_2x('\n');


oled_putc_2x('\t');
oled_putc_2x('\t');
oled_putc_2x('\t');

oled_putc_2x('W');
oled_putc_2x('o');
oled_putc_2x('r');
oled_putc_2x('l');
oled_putc_2x('d');

oled_refresh();

while(1){ // main loop
}
}

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