Elodin Aleph

Elodin Aleph

Aleph is an NVIDIA Jetson Orin-based flight computer running NixOS. The aleph/ directory contains NixOS modules, packages, and deployment tooling for composing a Linux flight software stack.

Quick Reference

# SSH into Aleph (USB-C rightmost port)
ssh root@fde1:2240:a1ef::1          # Default password: root

# SSH over WiFi (after setup)
ssh aleph-99a2.local                 # Hostname shown by `hostname` command

# Deploy configuration changes
./deploy.sh                          # Default: $USER@fde1:2240:a1ef::1
./deploy.sh root@aleph-99a2.local    # Custom SSH target

# Build SD image for fresh install
nix build --accept-flake-config .#packages.aarch64-linux.sdimage

Initial Setup

1. Connect USB-C to rightmost port on Aleph
2. ssh root@fde1:2240:a1ef::1 (password: root)
3. Follow aleph-setup wizard (or run it manually)
4. Connect to WiFi: iwctl station wlan0 connect "NetworkName"
5. Verify: ping google.com

After WiFi setup, SSH directly via aleph-XXXX.local.

Development Workflow

The recommended cycle for iterating on the NixOS configuration:

1. Edit files in aleph/flake.nix, aleph/modules/, or aleph/kernel/
2. Run ./deploy.sh from the aleph/ directory
3. The script builds, copies store paths, and activates the new config
4. To revert: reboot and select previous bootloader entry (requires serial console on left USB-C port)

NixOS Module System

Configuration is in aleph/flake.nix, composed from modules in aleph/modules/:

Hardware & Base

Flight Software Services

Setup & Status

Template flake.nix

aleph/template/flake.nix is the starting point for user configurations. It imports Aleph modules and configures services:

# Key structure in template/flake.nix
{
  inputs.elodin.url = "github:elodin-sys/elodin";

  outputs = { self, elodin, nixpkgs }: {
    nixosConfigurations.aleph = nixpkgs.lib.nixosSystem {
      modules = [
        elodin.nixosModules.aleph-base
        elodin.nixosModules.elodin-db
        elodin.nixosModules.mekf
        # ... other modules
      ];
    };
  };
}

Available FSW Applications

These Rust applications in fsw/ run as NixOS services on Aleph:

Fresh Install / Recovery

For unbootable or corrupted systems:

1. Build SD image: nix build --accept-flake-config .#packages.aarch64-linux.sdimage
2. Flash to USB: sudo dd if=aleph-os.img of=/dev/sdX bs=4M status=progress oflag=sync
3. Boot from middle USB-C port
4. SSH via rightmost USB-C: ssh root@fde1:2240:a1ef::1
5. Run aleph-installer
6. Remove USB and reboot

MCU Operations

# Reset the STM32 MCU
reset-mcu --app                    # Boot application firmware
reset-mcu --bootloader             # Enter ROM bootloader (BOOT0 high + NRST pulse)
reset-mcu --nrst-low               # Hold NRST low
reset-mcu --nrst-high              # Release NRST high
reset-mcu --boot0-high             # Hold BOOT0 high

# Flash firmware (default: UART via stm32flash)
flash-mcu --bin firmware.bin       # Flash binary to 0x08000000
flash-mcu --elf firmware.elf       # Flash ELF (objcopy to bin first)
# Override method: ALEPH_FLASH_MCU_METHOD=swd flash-mcu --elf firmware.elf

STM32H747 UART Flashing

The STM32 is flashed from the Orin via the ROM UART bootloader using stm32flash at 19200 8E1 on /dev/ttyTHS1. The NixOS service c-blinky-flash handles this automatically during deploy.sh.

Critical timing requirement: The STM32H747 ROM bootloader has a narrow interface detection window (~100ms) after NRST release. The stm32flash 0x7F sync byte must arrive during this window. If missed, the ROM falls to a dual-core sync handler and hangs forever. The flash-mcu.sh UART path handles this with tight timing: NRST low -> BOOT0 high -> NRST release -> 100ms -> stm32flash.

Tegra UART quirk: stm32flash cannot set termios flags on ttyTHS* devices. The script pre-configures the port with stty before calling stm32flash.

GPIO mapping (open-source expansion board):

• BOOT0: gpiochip0 line 144 (B2B pin 33)
• NRST: gpiochip0 line 106 (B2B pin 36)

STM32 Firmware (c-blinky)

fsw/c-blinky/main.c is bare-metal C for the STM32H747 CM7 core. Runs on HSI at 64MHz (no PLL). Outputs COBS-encoded EL log frames on USART1 PA9 (TX) at 115200 8N1. The serial-bridge service parses these frames and forwards them to elodin-db as aleph.stm32.log.

EL frame wire format: 0x00 | COBS(['E','L', ver=1, kind=1, level, ...msg...]) | 0x00

Built by Nix (aleph/pkgs/c-blinky.nix) using arm-none-eabi-gcc. Produces firmware.elf and firmware.bin.

Elodin-DB on Aleph

The elodin-db.nix module defaults to dbUniqueOnBoot = true, creating a fresh timestamped elodin-db instance on each deploy/boot at /db/default-YYYYMMDD-HHMMSS on port 2240. The elodin-db-default oneshot manages the lifecycle: it stops any old elodin-db@* template instances and waits for port 2240 to be free before starting the new one. The template service has stopIfChanged = false; restartIfChanged = false so NixOS activation never races with it. Set dbUniqueOnBoot = false for a single persistent /db/default instance.

Each fresh database ingests the shared asset root (services.elodin-db.assetsDir, default /var/lib/elodin/assets — the ELODIN_ASSETS tree seeded by the elodin module) via elodin-db run --assets, so a HITL recording carries its schematic assets under {db}/assets/ and is a complete, portable record: copy the /db/default-* directory off the vehicle and serve it anywhere with elodin-db run. Set assetsDir = null to disable ingest.

Connect from a development machine: elodin editor <aleph-ip>:2240

For SITL work against the same flight stack, examples/betaflight-sitl/ is the reference SITL example (Betaflight lockstep over UDP, recorded to a portable DB).

Key References

• Full setup guide: aleph/README.md
• Template configuration: aleph/template/flake.nix
• Sensor firmware: fsw/sensor-fw/README.md
• MSP OSD service: fsw/msp-osd/README.md