zig-duino

A tiny Zig workspace that builds both a host-side CLI and an AVR firmware using MicroZig. The firmware targets common Arduino Uno/Nano clones based on the ATmega328P and toggles the on-board LED (D13 / PB5).

Overview

Host app: zig-out/bin/zig_duino (a simple CLI built for your machine).
Firmware: zig-out/firmware/blink_avr.hex (for ATmega328P boards; LED on PB5/D13).
Toolchain: Zig 0.15.x + MicroZig for AVR.

Prerequisites

Zig 0.15.1 (check with zig version).
avrdude (for flashing). On Arch Linux: sudo pacman -S avrdude.
Serial access to /dev/ttyUSB0:
- Quick path: prefix commands with sudo.
- Recommended: add your user to the uucp group and re-login:
```
sudo usermod -aG uucp "$USER"
# log out/in or reboot for group to take effect
```
- Alternatively, grant a temporary ACL:
```
sudo setfacl -m u:$USER:rw /dev/ttyUSB0
```

Optional:

PlatformIO CLI (handy for listing ports):
```
pipx install platformio
pio device list
```

Build

Fetch dependencies (MicroZig) and build everything:

zig build --fetch
zig build

For AVR firmware, ensure ReleaseSmall optimizations when building:

zig build -Doptimize=ReleaseSmall

Artifacts:

Host CLI: zig-out/bin/zig_duino
Firmware HEX: zig-out/firmware/blink_avr.hex

Flashing the Board

Identify the serial port. Typical on Linux with CH340: /dev/ttyUSB0.

Probe the MCU signature and bootloader baud with avrdude (Uno/Nano clones use 57600 or 115200):

# Try 115200 first
avrdude -c arduino -p m328p -P /dev/ttyUSB0 -b 115200 -v
# If that fails, try 57600
avrdude -c arduino -p m328p -P /dev/ttyUSB0 -b 57600 -v

Expected signature for ATmega328P: 0x1E 0x95 0x0F.

Flash the firmware (two options):

Using avrdude directly:

avrdude -c arduino -p m328p -P /dev/ttyUSB0 -b 115200 -D \
  -U flash:w:zig-out/firmware/blink_avr.hex:i

Using the build-integrated flash step:

zig build -Doptimize=ReleaseSmall flash \
  -Dflash-port=/dev/ttyUSB0 \
  -Dflash-baud=115200 \
  -Dflash-programmer=arduino \
  -Davrdude-bin=avrdude \
  -Dflash-mcu=m328p

If you lack permissions on the serial device, prefix direct avrdude with sudo or fix permissions per Prerequisites.

Project Layout

build.zig: Builds the host app and configures MicroZig AVR firmware target.
build.zig.zon: Zig dependency manifest (pulls MicroZig).
src/main.zig: Host executable entry point.
src/root.zig: Library for host app.
src/firmware.zig: AVR blink firmware using MicroZig HAL (PB5/D13 toggle).
zig-out/: Build outputs. Firmware HEX in zig-out/firmware/.

Current State

Board detected as an Arduino-compatible with CH340 USB-serial.
AVR target assumed ATmega328P (Arduino Nano/Uno clone) @ 16 MHz.
Firmware builds and flashes successfully using avrdude at 115200 baud.
Output file present: zig-out/firmware/blink_avr.hex.

Troubleshooting

Permission denied on /dev/ttyUSB0:
- Add user to uucp group or use sudo/ACL as shown above.
avrdude sync errors:
- Toggle baud between 115200 and 57600.
- Press/reset the board at the start of the upload.
- Ensure you’re using -c arduino -p m328p for ATmega328P bootloaders.
Build errors on AVR regarding compiler_rt or odd integer sizes:
- Use -Doptimize=ReleaseSmall and avoid pulling in heavy helpers.
- This project disables bundling compiler_rt for the AVR firmware via build.zig.

Next Steps

Adjust the LED pin or board target in src/firmware.zig / build.zig if using a different AVR.
Add a serial "hello" example using USART via MicroZig HAL.
Create a flash build step that invokes avrdude automatically.

Maintained with Zig + MicroZig. Have fun hacking your Arduino-compatible in Zig!

jlucaso1/zig-duino