[avr-gcc-list] avr-gcc and char strings

[Andreas Höschler]

Hi all,

I am close to tearing my hair out. After having established the avr tool chain I tried out a very simple C-program (see below) on an SainSmart Mega2560 board programmed into the chip by making use of /Applications/Arduino.app//Contents/Resources/Java/hardware/tools/avr/bin/avrdude:

#define F_CPU 16000000UL  /* 16 MHz CPU clock */

#include "Global.h"

#include <util/delay.h>

#include <avr/io.h>

#include <avr/interrupt.h>

#include <inttypes.h>

 

char String[]  = "Hello world!!"; 

 

void USARTInit0(uint16_t baud)

{

    // Set Baud rate

    int value = (F_CPU / 16 / baud) - 1;

    UBRR0H = (uint8_t)(value>>8);

    UBRR0L = (uint8_t)value;

    

    // 8N1

    UCSR0C = 0x06; // (3<<UCSZ00);   

    

    // Enable receiver and transmitter

    UCSR0B = (1<<RXEN0) | (1<<TXEN0);

}

 

void TxByte0 (uint8_t data)

{

    // Wait for empty transmit buffer

    while ( !(UCSR0A & (1 << UDRE0)) );

   // Putting data into the buffer, forces transmission

   UDR0 = data;

}

 

int main (void)

  {

   DDRB = 0xff;          // all outputs

   

   USARTInit0(38400);       // 9600 19200 38400

      

   while (1)                 

     {            

      TxByte0('A');

      TxByte0('B');

      TxByte0('C');

      TxByte0('\n');

            

      char *s = String;   

      while (*s != 0)

        {

         TxByte0(*s);

         s++;

        }

      

      _delay_ms(500);            

     }

   return (0);

  }

 

This program produces the following output

...

ÿÿÿÿÿÿÿÿÿÿÿÿÿÿABC

ÿÿÿÿÿÿÿÿÿÿÿÿÿÿABC

ÿÿÿÿÿÿÿÿÿÿÿÿÿÿABC

...

 

telling me that sending single chars works but sending strings fails (does not seem to have anything to do with the serial communication but rather be some kind of memory management problem!??).

To be sure the problem is not caused by my own gcc build I changed my Makefile to 

# AVR-GCC Makefile

PROJECT=toggle_led

SOURCES=main.c

HEADERS=

CC=/Applications/Arduino.app//Contents/Resources/Java/hardware/tools/avr/bin/avr-gcc

OBJCOPY=avr-objcopy

MMCU=atmega2560

 

CFLAGS=-mmcu=$(MMCU) -Wall -O2 -I /usr/local/avr/include

$(PROJECT).hex: $(PROJECT).out

$(OBJCOPY) -j .text -O ihex $(PROJECT).out $(PROJECT).hex

 

$(PROJECT).out: $(SOURCES)

$(CC) $(CFLAGS) -I./ -o $(PROJECT).out $(SOURCES)

 

program: $(PROJECT).hex

avrdude  -p $(MMCU) -c avrispmkII -P usb -e -U flash:w:$(PROJECT).hex

clean:

rm -f $(PROJECT).out

rm -f $(PROJECT).hex

and thus built the program with a gcc from a respected source (avr-gcc coming with Arduino.app). But the problem persists!? I already discussed this problem on avrfreaks forum. All agree that the above code should work but it does not!?? :-()

Could this be a problem of the board/chip? I am using a SainSmart Mega2560 board (which seems to be a clone of the original Arduino product)! Or am I doing anything wrong??

 

Clueless!?? :-( Hints are greatly appreciated!!

Thanks a lot,

 

 Andreas