Build for another machine

At the end of this page you have an aarch64 build of the crate and its examples for a Raspberry Pi 4 or 5 or another 64-bit ARM Linux machine, made and smoke-tested on an x86-64 box. The target needs a 64-bit system (Raspberry Pi OS 64-bit or Ubuntu arm64); 32-bit armhf systems are not supported.

Validation status: the aarch64 binaries of both targets below have run the crate’s test suite under qemu-aarch64-static against the simulator, with byte-identical model numbers. They have not yet run on a physical Raspberry Pi and not against a robot.

The two targets

The default model-library feature compiles Robot::load_model_from_robot, which dlopens the model library an FER serves. That library is an x86-64 build (libfcimodels_x64.so) and of no use on aarch64 either way; load_model() evaluates both robots’ models natively and is the path to use. Turning the feature off drops libloading, which a static musl binary cannot use, and changes nothing else.

Option A: cargo-zigbuild, no root

rustup target add aarch64-unknown-linux-gnu
python3 -m venv ~/.venvs/zigbuild && source ~/.venvs/zigbuild/bin/activate
pip install ziglang
cargo install cargo-zigbuild

cargo zigbuild --release --target aarch64-unknown-linux-gnu -p franka-rs --examples

The bundled zig cc is linker and sysroot; the result is an ordinary dynamically linked aarch64 binary with the default features.

Option B: a system cross compiler

sudo apt install gcc-aarch64-linux-gnu   # Debian/Ubuntu
rustup target add aarch64-unknown-linux-gnu
CARGO_TARGET_AARCH64_UNKNOWN_LINUX_GNU_LINKER=aarch64-linux-gnu-gcc \
  cargo build --release --target aarch64-unknown-linux-gnu -p franka-rs --examples

This is what CI’s aarch64-cross-build job does; the linker can also go in .cargo/config.toml.

Option C: a static musl binary, no cross linker

Rust’s musl target ships a self-contained linker (rust-lld) with rustup:

rustup target add aarch64-unknown-linux-musl
cargo build --release --target aarch64-unknown-linux-musl -p franka-rs \
  --no-default-features --examples

The repository’s .cargo/config.toml sets linker = "rust-lld" for this target only; outside the checkout pass RUSTFLAGS="-C linker=rust-lld". The result is one statically linked binary per example with no runtime dependencies.

Smoke test without hardware

qemu-aarch64-static (package qemu-user-static) runs the binaries on the x86-64 host. A static musl binary needs nothing else:

qemu-aarch64-static target/aarch64-unknown-linux-musl/release/examples/communication_test
# Usage: .../communication_test <robot-hostname>

A dynamically linked glibc binary also needs an aarch64 sysroot, for example the /lib and /usr of an arm64 base image:

cid=$(docker create --platform linux/arm64 arm64v8/ubuntu:24.04)
mkdir sysroot && docker cp $cid:/lib sysroot/ && docker cp $cid:/usr sysroot/
docker rm $cid
qemu-aarch64-static -L sysroot target/aarch64-unknown-linux-gnu/release/examples/communication_test

The crate’s test suite has been run this way, one binary at a time with --test-threads=1 and FRANKA_SIM_ADDR=127.0.0.1 pointing at a container started on the host (a binary under QEMU cannot exec the host’s docker, so the harness must attach). Everything that passes natively passed on aarch64 with byte-identical model numbers, except the tests calling load_model_from_robot: compiled out under --no-default-features, and failing with the feature on because the x86-64 library cannot be loaded.

Deploy and run

scp target/aarch64-unknown-linux-gnu/release/examples/communication_test pi@<pi-host>:~/
ssh pi@<pi-host> chmod +x ~/communication_test

# on the target
FRANKA_REALTIME=ignore ./communication_test 172.16.0.2

The same realtime prerequisites apply on the target: a PREEMPT_RT kernel (cat /sys/kernel/realtime reads 1) and the right to SCHED_FIFO, or FRANKA_REALTIME=ignore at the cost described there. Raspberry Pi OS 64-bit has a PREEMPT_RT kernel package (sudo apt install linux-image-rpi-v8-rt, selected with kernel=kernel8_rt.img in /boot/firmware/config.txt) and Ubuntu 24.04 for Raspberry Pi has one through Ubuntu Pro (sudo pro enable realtime-kernel --variant=raspi); neither has been exercised with this crate yet.

Building natively on the target instead (rustup, then cargo build --release -p franka-rs --examples) needs none of the above; it has not been tried on a Pi yet.