将多个目标文件链接到二进制AVR GCC

Question

I have the following headers and source files:

AVR_comunic.h

#ifndef AVR_COMUNIC_H_
#define AVR_COMUNIC_H_

#include<avr/io.h>

#define FOSC 20000000UL // Clock Speed
#define BAUD 19200
#define MYUBRR FOSC/16/BAUD-1

void USART_Init( unsigned int);
int USART_WriteChar(unsigned char);
// int USART_Receive( unsigned char *);
void USART_Flush(void);

#endif /* AVR_COMUNIC_H_ */

AVR_comunic.c

#include "AVR_comunic.h"

void USART_Flush( void )
{
    ...
}

void USART_Init( unsigned int ubrr)
{
    ...
}

int USART_WriteChar(unsigned char data)
{
   ...
}

and main_f.c

#include"AVR_comunic.h"

void init_ports()
{
    DDRD|= (1<<PD7);
}

int main(void)
{
    init_ports();
    ...
    while(1)
    {
        // now what?
    }
return 1;
}

I wrote a batch file in Notepad++ to obtain the .hex file for this program

COMPILE_BUILD.bat

ECHO OFF
ECHO ----------------------------------------------------------
ECHO ----- executing your commands : compile and build  -------
ECHO ----------------------------------------------------------
avr-gcc -g -Wall -Os -DF_CPU=20000000UL -mmcu=atmega88p -c AVR_comunic.c 
avr-gcc -g -Wall -Os -DF_CPU=20000000UL -mmcu=atmega88p -c main_f.c

avr-gcc -g -mmcu=atmega88p -o AVR_comunic.elf main_f.o AVR_comunic.o

avr-objdump -h -S AVR_comunic.elf > AVR_comunic.lst
avr-gcc -g -mmcu=atmega8 -Wl,-Map,AVR_comunic.map -o AVR_comunic.elf AVR_comunic.o
avr-objcopy -j .text -j .data -O ihex AVR_comunic.elf AVR_comunic.hex
ECHO ----------------------------------------------------------
ECHO ---------------------- happy ? ---------------------------
ECHO ----------------------------------------------------------
pause

I get the following error:

... : undefined reference to 'main'
avr-objcopy: 'AVR_comunic.elf' no such file

I understand from the information on internet that the linker does thinks that there is no "main" function ... but it is ... what am I doing wrong? Or how should I write to compile multiple source files?

Answer 1

I understand from the information on internet that the linker does thinks that there is no "main" function ... but it is ... what am I doing wrong?

This command:

avr-objdump -h -S AVR_comunic.elf > AVR_comunic.lst

attempts to extract info from AVR_communic.elf , which isn't produced yet. You want to move it after this command:

avr-gcc -g -mmcu=atmega8 -Wl,-Map,AVR_comunic.map -o AVR_comunic.elf AVR_comunic.o

The above command fails with undefined reference to: 'main' because you are not linking main_f.o into it.

It appears that what you really want is:

avr-gcc -g -mmcu=atmega88p -o AVR_communic.elf main_f.o AVR_comunic.o
avr-objdump -h -S AVR_comunic.elf > AVR_comunic.lst
avr-objcopy -j .text -j .data -O ihex AVR_comunic.elf AVR_comunic.hex