5.5 Cannot load hbm model

What “hbm” is

hbm packages BPU-ready weights for RDK boards (usually .hbm). Only board-side inference (YOLO, detection, segmentation samples, etc.) needs them.

Pure SSH/files/desktop/local LLM use generally never touches hbm.

Typical failures

YOLO/detection launches log lines like:

• No such file or directory: config/xxx.hbm
• model not found
• cannot open model: <path>
• Silent immediate exit 0
• hbm version mismatch / model incompatible

Quick triage

On the board locate real artifacts:

find /opt/tros -name "*.hbm" 2>/dev/null

Remap launches that use relative paths (config/foo.hbm) to the absolute path find prints.

Don’t rely on relative paths

Launches probe config/*.hbm from the process cwd, which differs by invocation.

Files usually live under /opt/tros/humble/lib/<package>/config/ or share/<pkg>/config/. Prefer absolute paths.

Three fixes

A — Absolute path (most reliable)

model_file_path = '/opt/tros/humble/lib/hobot_yolo_world/config/yolo_world_v2.hbm'

Pros: deterministic. Cons: relocate per board/path changes.

B — ros2 pkg share path (better portability)

import os
from ament_index_python.packages import get_package_share_directory

model_file_path = os.path.join(
    get_package_share_directory('hobot_yolo_world'),
    'config',
    'yolo_world_v2.hbm'
)

Pros: works across setups if ROS finds the package. Cons: ROS index must resolve the pkg.

C — Stable symlink when cwd varies

# Run once on board
mkdir -p /userdata/models
ln -sf /opt/tros/humble/lib/hobot_yolo_world/config/yolo_world_v2.hbm /userdata/models/yolo.hbm

# launch snippet
model_file_path = '/userdata/models/yolo.hbm'

Pros: writable fixed path. Cons: extra indirection.

Board compatibility

Different RDK SoCs expose different BPU ISAs — you cannot reuse hbm across board families. Rough guide:

Board	BPU ISA	Portable across boards?
RDK X3	Bernoulli2	No
RDK X5	Bayes	No (not interchangeable with X3/S100)
RDK S100	Nash	No

Treat toolchain/board docs as authoritative.

For hbm version mismatch / model incompatible, rebuild hbm targeting the active board.

Root cause

ROS 2 launches inherit cwd from invocation context:

• ros2 launch from a shell ⇒ that shell cwd
• daemons ⇒ service-defined cwd
• editor terminal vs SSH ⇒ may differ

So relative hbm lookups are flaky.

Operational practices

Practice	Why
Ban relative paths in reviewed launches	Keeps onboarding predictable
Keep core models under /opt/tros/humble/lib/<pkg>/config/	ROS‑standard placement
Custom weights in writable areas	e.g. /userdata/models/ survives many SD swaps
Per-board binaries in CI	Produce one hbm per SKU