Electronic – arduino – AVR. How to configure as output just one pin

arduinoavrc

In AVR C code, if you want to declare some port as ouput, you just have to to do this:

DDRB = 0xFF;

But how can I do if I want to declare as ouput just one pin. For example, I want to declare has output Arduino's pin 13, which corresponds to PB5.

I know I can declare that in binary format:

DDRB = b11111111;

But, I don't know which bit position corresponds to PB5.

Thanks in advance, I could not find this answer in Google.

Best Answer

PB5 is the 6th bit.
Just remember that the numbering is zero-based and starts with the least-significant-bit on the right, so the value you're looking for in this case is 0b00100000.
When you're setting this bit, you'll probably want to use a logical OR operation instead of a simple assignment, so:

DDRB |= 0b00100000;

instead of

DDRB = 0b00100000;

That way you won't inadvertently clear any of the other bits which might already be set.

Related Solutions

Electronic – How to create a static library for the AVR Atmega328p

The AVR-Libc user manual has an entire chapter on how to build a library. I would suggest starting there. If you use an IDE like eclipse, there will be project settings that are applicable if you want to build as a library instead of an executable.

Edit

Here's what eclipse does when I set it up for your example:

So that it couldn't be trivially compiled away, I changed your test_function to:

#include "test.h"

void test_function()
{
    volatile int i = 0;
    i++;
}

Building the library:

avr-gcc -Wall -g2 -gstabs -Os -fpack-struct -fshort-enums -std=gnu99 -funsigned-char -funsigned-bitfields -mmcu=atmega328p -DF_CPU=16000000UL -MMD -MP -MF"test.d" -MT"test.d" -c -o"test.o" "../test.c"

avr-ar -r "libtest.a"  ./test.o 

avr-objdump -h -S libtest.a  >"libtest.lss"

avr-size --format=avr --mcu=atmega328p libtest.a

Building the main program

avr-gcc -I"C:\path\to\my\workspace\test" -Wall -g2 -gstabs -Os -fpack-struct -fshort-enums -std=gnu99 -funsigned-char -funsigned-bitfields -mmcu=atmega328p -DF_CPU=16000000UL -MMD -MP -MF"program.d" -MT"program.d" -c -o"program.o" "../program.c"

avr-gcc -Wl,-Map,MainProgram.map -L"C:\path\to\my\workspace\test\Release" -mmcu=atmega328p -o"MainProgram.elf"  ./program.o   -ltest

avr-objdump -h -S MainProgram.elf  >"MainProgram.lss"

avr-size --format=avr --mcu=atmega328p MainProgram.elf

... and it builds without error. My guess is you need include paths specified in the command lines. Following proper naming conventions is pretty important too, try and follow the pattern above. Obviously the avr-objdump and avr-size commands are just for more information and not required if you're just building.

I'm pretty certain that if you'll need to recompile your library for specific target architectures and clock speeds as well.

Electronic – How to use AVR ADC with multiplier

int can only be 0-255

That's not correct. In the C programming language, an int is always at least 16 bits wide, even on 8-bit micros. A char is 8 bits wide.

But when using inttypes.h, I strongly recommend using the explicit types like uint8_t,int16_t or uint32_t.

Your real error is using _delay_ms() with a variable parameter. This is not allowed, as it is a macro involving floating point calculations - at least in avr gcc. You are supposed to use something like this:

void DelayMs(int delay) {
  while(delay--) _delay_ms(1);
}

Best Answer

Related Solutions

Electronic – How to create a static library for the AVR Atmega328p

Electronic – How to use AVR ADC with multiplier

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