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ATmega32 Development Shell

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this is my college lab notes for Semester 5 subject Embedded System Development that mainly goes over basics of low level system architecture and development of atmega32 on a simulator like proteus or simulide( this notes focuses on development with the simulide)

before starting we need to setup a development enviroment for using simulide, avr-libc, GCC compiler with avr compatability. we can do this by creating a simple devshell using nix

devshell for ATmega32

writing a devshell for ATmega32 is similar to making any other devshell for other languages or development but with only one major difference, in ATmega32 we need native build packages x86_64 aswell as cross compiled packages avr

avr packages
avr-gcc: gcc compiler compatable with avr
avr-libc: standard C-library for avr
binutils: build against avr
x86_64 package
simulide: for simulating ATmega32 chip

{
  description = "devshell for ATmega32 development";
 
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    flake-utils.url = "github:numtide/flake-utils";
  };
 
  outputs = { self, nixpkgs, flake-utils, ... }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = nixpkgs.legacyPackages.${system};
        cross = pkgs.pkgsCross.avr;
      in {
        devShells.default = pkgs.mkShell {
          name = "avr-devshell";
 
          buildInputs = [
            cross.buildPackages.gcc
            cross.buildPackages.binutils
            cross.avrlibc
            pkgs.simulide
          ];
 
          shellHook = ''
            echo "AVR dev shell active"
            echo "CC = $CC"
            echo "AR = $AR"
            echo "Simulide binary: $(which simulide)"
          '';
 
        };
      });
}
nix develop . # activate the devshell from the flake dir

after executing the devshell activation, you will enter the devshell with all the required dependencies installed. to check if all is working correctly we can run a simple C program.

AVR C program to toggle a led at PB0

#include <avr/io.h>
#include <util/delay.h>
 
int main(void) {
    DDRB |= (1 << 0); // PB0 as output
    for(;;) {
        PORTB ^= (1 << 0); // Toggle LED
        _delay_ms(500);
    }
}

you can compile this code snippet by:

$ avr-gcc -mmcu=atmega32 -Os -o main.elf main.c
$ avr-objcopy -O ihex -R .eeprom main.elf main.hex

this will generate an intel hex binary with stripped eeprom daa for our toggle program that we then can use on simulide.

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