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Assembler - the DNA of Computers
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AVR Assembler Toolbox
AVR plugin for assembler code compilation, linking, size reporting, and uploads directly from Visual Studio Code.
AVR Assembler Toolbox is a lightweight Visual Studio Code extension for building and uploading AVR assembly (.s) projects using the GNU AVR toolchain.
It provides a minimal, fast workflow similar to PlatformIO, but focused on pure assembler development.
Features
- 🔨 Assemble
.s → .o
- 🔗 Link
.o → .elf (supports -nostartfiles)
- 📦 Convert
.elf → .hex
- 📊 Display memory usage (
avr-size)
- ⬆ Upload firmware via
avrdude
- 🔌 Auto-detect serial ports
- ⚙ Configurable toolchain paths
- ❗ Clickable compiler errors (Problems panel integration)
- 📌 Status bar buttons for quick actions
📁 Supported Files
- AVR assembly source files with extension:
.s
Requirements
To use AVR Assembler Toolbox, ensure the following tools and environment are available.
This extension depends on the standard AVR GNU toolchain. The following tools must be installed and accessible from your system PATH:
avr-gcc – compiler/assembler and linkeravr-objcopy – converts ELF files to HEX formatavr-size – displays memory usageavrdude – uploads firmware to the target device
Installation (Ubuntu / Debian)
sudo apt update
sudo apt install gcc-avr binutils-avr avr-libc avrdude
Installation (Arch Linux)
sudo pacman -S avr-gcc avr-binutils avr-libc avrdude
Installation (macOS with Homebrew)
brew tap osx-cross/avr
brew install avr-gcc avrdude
Installation (Windows)
- Install WinAVR, AVR-GCC toolchain, or use MSYS2
- Ensure all required tools are added to your system
PATH
🖥️ Visual Studio Code
- Visual Studio Code version 1.110.0 or newer
- This extension must be installed and enabled
🔌 Hardware (for upload)
To upload firmware using avrdude, you will need:
- A supported AVR microcontroller (e.g. ATmega328P)
- A compatible programmer or bootloader (e.g. Arduino bootloader)
- A valid serial/USB port:
| Platform |
Example Ports |
| Linux |
/dev/ttyUSB0, /dev/ttyACM0 |
| macOS |
/dev/tty.*, /dev/cu.* |
| Windows |
COM3, COM4, etc. |
The upload port can be configured manually in settings or selected using:
AVR: Select Upload Port
⚙️ Optional Configuration
If the AVR toolchain is not available in your system PATH, you can configure explicit paths in settings:
{
"avr-asm-builder.avrGccPath": "/path/to/avr-gcc",
"avr-asm-builder.avrObjcopyPath": "/path/to/avr-objcopy",
"avr-asm-builder.avrSizePath": "/path/to/avr-size",
"avr-asm-builder.avrdudePath": "/path/to/avrdude"
}
or using settings as described below.
Extension Settings
This extension contributes the following settings under the avr-asm-builder namespace.
You can configure them via:
- Settings UI → search for
AVR ASM Builder
- or directly in
settings.json
⚙️ Available Settings
"avr-asm-builder.avrGccPath": "avr-gcc"
Path or command name for avr-gcc.
"avr-asm-builder.avrObjcopyPath": "avr-objcopy"
Path or command name for avr-objcopy.
"avr-asm-builder.avrSizePath": "avr-size"
Path or command name for avr-size.
"avr-asm-builder.avrdudePath": "avrdude"
Path or command name for avrdude.
🧠 Target Configuration
"avr-asm-builder.mcu": "atmega328p"
Target MCU passed to:
avr-gcc via -mmcuavrdude via -p
"avr-asm-builder.useNoStartFiles": true
If enabled, uses -nostartfiles during linking (recommended for pure assembly projects).
📁 Build Configuration
"avr-asm-builder.outputDirectory": "build"
Directory where build artifacts are stored (.o, .elf, .hex).
🔌 Upload Configuration
"avr-asm-builder.avrdudeProgrammer": "arduino"
Programmer passed to avrdude via -c.
"avr-asm-builder.avrdudePort": "/dev/ttyUSB0"
Serial/USB port used for uploading firmware.
You can:
- set it manually
- or use command:
AVR: Select Upload Port
"avr-asm-builder.avrdudeBaud": 115200
Baud rate used for uploading via avrdude.
📝 Example Configuration
{
"avr-asm-builder.mcu": "atmega328p",
"avr-asm-builder.avrGccPath": "/usr/bin/avr-gcc",
"avr-asm-builder.avrObjcopyPath": "/usr/bin/avr-objcopy",
"avr-asm-builder.avrSizePath": "/usr/bin/avr-size",
"avr-asm-builder.avrdudePath": "/usr/bin/avrdude",
"avr-asm-builder.avrdudePort": "/dev/ttyACM0",
"avr-asm-builder.avrdudeProgrammer": "arduino",
"avr-asm-builder.avrdudeBaud": 115200,
"avr-asm-builder.outputDirectory": "build",
"avr-asm-builder.useNoStartFiles": true
}
💡 Notes
- All tool paths can be either:
- command names (if available in
PATH)
- or absolute paths
- Settings can be defined:
- globally (user settings)
- per project (
.vscode/settings.json)
- Changes take effect immediately (no restart required)
Example
Below is a minimal AVR assembly example that blinks the built-in LED on Arduino Uno (ATmega328P, PB5 / pin 13).
Create a file named main.s:
.org 0x0000
rjmp RESET
DDRB =0x04
PORTB =0x05
RESET:
ldi r16, 1 << 5 ; Set bit 5
out DDRB, r16 ; Set PB5 as output
LOOP:
sbi PORTB, 5 ; Turn LED on
rcall delay
cbi PORTB, 5 ; Turn LED off
rcall delay
rjmp LOOP
delay:
ldi r20, 60 ; Outer loop
outer_loop:
ldi r18, 250 ; Mid loop
mid_loop:
ldi r19, 250 ; Inner loop
inner_loop:
dec r19
brne inner_loop
dec r18
brne mid_loop
dec r20
brne outer_loop
ret
How to run
- Open
main.s in Visual Studio Code
- Click AVR Build in the status bar or run:
AVR: Build Current .s File
- Upload to your device:
AVR: Upload Current HEX
Notes
- The example configures PB5 (Arduino pin 13) as output.
- A simple software delay loop is used for timing.
- Make sure your settings match your hardware:
avr-asm-builder.mcuavr-asm-builder.avrdudePort
Known Issues
Linking errors (e.g. unknown identifier such as label) do not guide you to the source file when clicking an error in the output console.
Release Notes
0.1.0
Initial release for public
0.1.9
RC-1 version with sidebar, icons, documentation and settings
About the project:
The MultiASM project has been co-funded by the European Union. Views and opinions expressed are however those of the author or authors only and do not necessarily reflect those of the European Union or the Foundation for the Development of the Education System. Neither the European Union nor the entity providing the grant can be held responsible for them.
MultiASM website
KA220-HED – Cooperation partnerships in higher education
Project ID: 2023-1-PL01-KA220-HED-000152401
Project implementation period: from 2023.12.01 to 2026.11.30 (36m)
Enjoy!
