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

[Senthil Kumar Selvaraj]

On Thu, Dec 04, 2014 at 03:45:20AM +0530, Andreas Höschler wrote:
> Hi Wouter,
> 
> here is the assembler file generated with
> 
> avr-gcc -mmcu=atmega2560 -Wall -O2 -S -I /usr/local/avr/include -I./ -o 
> toggle_led.out main.c
> 
> 
> Thanks!!
> 
> Andreas
> +
> 
> Could you post the assembler output? IIRC --save-temps or -S should be added 
> to the gcc command line.
> 
> Wouter
> 
> Op 3 dec. 2014 22:12 schreef "Andreas Höschler" 
> <address@hidden<mailto:address@hidden>>:
> 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!??).

Older versions of the toolchain did not tell the linker where to place
globals in data memory (i.e. did not pass -Tdata) - that would obviously
break globals.

Can you try making String local and see if that helps? Can you also send
the output ELF (or atleast disassembly (objdump -S) and sections
(objdump -h))?

Regards
Senthil

> 
> 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
> 
> 
> 
> 
> 
> _______________________________________________
> AVR-GCC-list mailing list
> address@hidden<mailto:address@hidden>
> https://lists.nongnu.org/mailman/listinfo/avr-gcc-list
> 
>