avr-samples

This repository is intended to contain detailed instructions on how to get started with programming Atmel AVR microcontrollers. It also contains a bunch of thoroughly documented and explained example projects.

Running the code

This repository contains several folders. Each of those folders is a self-contained project that can be opened either in Atmel Studio or VS Code.

The fast & easy way to get started: wire everything up properly, connect the MCU (micro-controller unit) to your PC using a USBasp programmer.

0. Wire up your circuit correctly on the breadboard.
1. Connect the MCU to your PC using a USBasp programmer
2. cd <on of the project>, for example cd blink
3. make flash

What Makefiles do, explained

Compile .c files

First, you need to compile a C source file to an .elf object file.

avr-gcc -mmcu=atmega8 -Wall -Os -o blink.elf blink.c -DF_CPU=1000000UL

DF_CPU=1000000UL sets F_CPU to 1MHz.

Convert .elf files to .hex files

To flash the MCU using USBasp programmer, you need a .hex file. It can be created out of the .elf file you generated in the previous step.

avr-objcopy -j .text -j .data -O ihex blink.elf blink.hex

Flash

Now it's time to run the code

avrdude -c usbasp -p m8 -e -U flash:w:blink.hex

Setup with VSCode

macOS

First things first: you need Homebrew.

1. Install avrdude - a small program used to flash AVR microcontrollers

   brew install avrdude

2. Install avr-gcc - an AVR-flavor of GNU GCC

   brew tap osx-cross/avr

   brew install avr-gcc

3. Install a C/C++ Extension for VSCode

4. To make VSCode's IntelliSense detect AVR header files, make the editor aware of them. For this, you'll need to know the exact version of your avr-gcc installation: brew ls avr-gcc

It prints a list which contains:

/usr/local/Cellar/avr-gcc/<version>/avr/include/

Copy that line, replacing with your version.

Now, in project root, create a .vscode folder. In it, create settings.json file with the following content:

Example (for avr-gcc v9.3.0 and using headers for ATmega8A)

{
  "C_Cpp.default.includePath": [" /usr/local/Cellar/avr-gcc@9/9.3.0_2/avr/include/"],
  "C_Cpp.default.defines": ["__AVR_ATmega8A__"]
}

Voilà, IntelliSense should work now.

Windows

1. Install avr-gcc - an AVR-flavor of GNU GCC. This version (which we recommend ) contains also avrdude, make and a couple other GNU tools, so you won't have to install them separately. Install it to your home directory (e.g C:\Users\Bartek) so that it'll be easy to find - in our case, it's C:\Users\Bartek\avr-gcc

2. Add the location where you installed avr-gcc to $PATH (how to add items to path on Windows?)

3. Install a C/C++ Extension for VSCode

4. To make VSCode's IntelliSense detect AVR header files, make the editor aware of them. For this, you'll need to know the exact location of your avr-gcc installation. In our case it was C:\Users\Bartek\avr-gcc. To that location, we need append \bin, like this: C:\Users\Bartek\avr-gcc\bin

Example (using headers for ATmega8A)

.vscode/settings.json

{
  "C_Cpp.default.includePath": ["C:\\Users\\Bartek\\avr-gcc\\avr\\include"],
  "C_Cpp.default.defines": ["__AVR_ATmega8A__"]
}

This is almost enough, but chances are, if you use sei() or ISR functions for interrupts, your IntelliSense will show errors. To fix them, create a new file named c_cpp_properties.json in .vscode directory in this project's root with the following content:

.vscode/c_cpp_properties.json

{
  "configurations": [
    {
      "name": "Win32",
      "includePath": ["${default}"],
      "cStandard": "c99",
      "cppStandard": "c++17",
      "intelliSenseMode": "gcc-x64"
    }
  ],
  "version": 4
}

Voilà, IntelliSense should work just fine.

Useful resources

• mikrokontrolery.blogspot.com by dondu

• ATmega8 datasheet by dondu

• ATmega328p datasheet

• Setting up VSCode for AVR development

• avr-libc manual

  A bit old but this stuff doesn't change very often. Useful sections:

  • 6.36 Compiling and linking