Piksi Multi Buildroot

Buildroot configuration and packages for building the Piksi Multi system image.

Overview

piksi_buildroot is a Buildroot project targeting the Piksi Multi GNSS receiver. It consists of

• Buildroot, as a git submodule
• An external Buildroot tree in the top-level piksi_buildroot directory:
  • Buildroot configuration in configs
  • Custom packages in package
  • Board-specific files (rootfs overlay, device trees, scripts, etc.) in board/piksiv3

Building

Docker

Install Docker for your platform.

Run

# Set up Docker image
make docker-setup
# Download firmware and FPGA binaries
make docker-make-firmware
# Build the system image in a Docker container
make docker-make-image

Images will be in the buildroot/output/images folder.

Linux Native

Ensure you have the dependencies. See Dockerfile for build dependencies.

Run

# Initialize submodules
git submodule update --init --recursive
# Download firmware and FPGA binaries
make firmware
# Build the system image
make image

Images will be in the buildroot/output/images folder.

Incremental Builds

It is possible to rebuild individual packages and regenerate the system image. Note that Buildroot does not automatically rebuild dependencies or handle configuration changes. In some cases a full rebuild may be necessary. See the Buildroot Manual for details.

Docker

Build shell

# Start interactive Docker container
make docker-run
# Rebuild a package
make -C buildroot libpiksi-rebuild
# Rebuild the system image
make image

One-shot make target

To do an incremental rebuild of a package, invoke the following:

make docker-pkg-<package_name>-rebuild

Where <package_name> is a package name like ntrip_daemon. To get an idea of what other commands are available for a package, inspect the help output from buildroot:

# Launch the build shell
make docker-run
# Ask buildroot for help
make -C buildroot help

Linux Native

# Enter buildroot directory
cd buildroot
# Set BR2_EXTERNAL to the piksi_buildroot directory
export BR2_EXTERNAL=..
# Rebuild a package
make libpiksi-rebuild
# Rebuild the system image
make image

Building the sample daemon

In order to build the sample daemon located here, set the BR2_BUILD_SAMPLE_DAEMON environement variable to y in the build environment:

export BR2_BUILD_SAMPLE_DAEMON=y

Then build normally:

# Docker
make docker-make-image

# or, Linux native
make image

Fetching firmware binaries

To build a production system image, the build process expects the following firmware and FPGA binaries to be present:

firmware/prod/piksi_firmware.elf
firmware/prod/piksi_fpga.bit
firmware/microzed/piksi_firmware.elf
firmware/microzed/piksi_fpga.bit

You can use the following command to download these binaries from S3. Note that this requires awscli to be installed and AWS credentials to be properly configured if you are building from a non-release branch.

# Docker
make docker-make-firmware # (Requires 'make docker-setup` to be run first)

# Linux native
make firmware

Check fetch-firmware.sh to see which image versions are being used.

Note that these binaries are only used by the production system image. In the development system image they are instead read from the network or SD card.

Copying data out of docker

For speed, most buildroot data is captured inside a docker volume. The volume keeps file access inside a docker container instead of moving the data from container to host (which is slow on many platforms, except Linux).

The following diagram shows how Docker composes the file system layers that we specify for the build container:

  ┌────────────────────────────────────────────────┐
  │                                                │
  │ Host Filesystem                                │          Initially
  │   ($PWD mapped to /piksi_buildroot)            │       populated with
  │                                                │         contents of
  └──────┬─────────────────────────────────────────┘ ┌──── $PWD/buildroot,
         │                                           │    changes are only
         │        ┌──────────────────────────────┐   │       visible in
         │        │  Docker volume:              │   │         docker.
         ├───────▶│    (/buildroot/)             │◀──┘
         │        └──────────────────────────────┘
         │                                               Anything written
         │        ┌──────────────────────────────┐       here will show up
         │        │ Container to host mapping:   │  ┌───    in the host
         ├───────▶│   (/buildroot/output/images) │◀─┘       filesystem.
         │        └──────────────────────────────┘
         │
         │        ┌──────────────────────────────┐
         │        │ Ephemeral container layer    │       Anything that doesn't
         └───────▶│                              │◀─┐      match an existing
                  └──────────────────────────────┘  │       mapping will be
                                                    └───    captured in an
                                                          ephemeral (per run)
                                                                layer.

To copy data out of docker, use the following make rule:

make docker-cp SRC=/piksi_buildroot/buildroot/output/target/usr/bin/nap_linux DST=/tmp/nap_linux