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Rust for embedded development

Intended for Embassy development, this VM sets up:

  • Rust compilation targets (ESP32-C3, ESP32-C6)
  • probe-rs-remote: connection to an external computer with probe-rs and espflash installed

Overall

You'll be connecting the development kit (e.g. ESP32-C6-DevKitC) to another computer; either a Raspberry Pi or a Linux PC, which needs to have probe-rs and espflash installed.

This gives the benefit that your development board is galvanically isolated from the development system, where you run your IDE etc. If something were to go wrong with electronics (read: SMOKE!), you'll appreciate this!

Note

With Multipass we'd need some way of passing USB over IP anyhow, since Multipass does not support USB device mapping.

Preparations

If you already have the assisting computer (Raspberry Pi) set up, great! Feed its ssh user and IP to the creating script, below.

If you don't, visit probe-rs-remote to see how to set things up.

Usage

Create the VM by:

$ [PROBE_RS_REMOTE={user@ip}] rust+emb/prep.sh
...
VM is ready.

Mounting work folders

The idea is that your software would remain on the host disk, shared with the Multipass VM (where the development tools sans IDE reside).

Say you have a folder /Some/path/to/circus. This is how to share it with the VM, as ~/circus.

Note: We use "native" folder sharing, which is said to be faster than the default. It does, however, need the VM to be stopped when mounts are added/removed.

[host]$ multipass stop rust-emb

[host]$ multipass mount --type=native /Some/path/to/circus rust-emb:

[host]$ multipass shell rust-emb

Finishing probe-rs tunneling

You can already use the VM to build embedded Rust code, but to flash them onto a hardware device, probe-rs tunnelling needs to be set up.

Note

We don't do this automatically, since that would mean you must have the assistant computer available by the time you run prep.sh. That might not be the case; or perhaps you just wish to have a build environment.

Enter the VM:

$ multipass shell rust-emb

What is needed is:

  1. Confirm the PROBE_RS_REMOTE value

    $ echo $PROBE_RS_REMOTE
[email protected]

    Is this the ssh user and IP, to reach your Raspberry Pi?

    If so, carry on.

    If not, prepare it by editing ~/.bashrc (and . ~/.bashrc to bring in the changes).

  2. Copy over the ssh public key

    prep.sh has already created a key-pair we can use for the authentication (see it with ls -al ~/.ssh).

    $ ssh-copy-id $PROBE_RS_REMOTE
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/home/ubuntu/.ssh/id_ed25519.pub"
The authenticity of host '192.168.1.199 (192.168.1.199)' can't be established.
ED25519 key fingerprint is SHA256:d+UMTm6/gW9NtWmBFG8mDXVgkTGmAaN6PVesgHxZQUg.
This key is not known by any other names.
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
[email protected]'s password: 

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh '[email protected]'"
and check to make sure that only the key(s) you wanted were added.

    You enter the yes and the password to the assistant computer.

Now, you should be able to:

$ probe-rs list
No debug probes were found.

Attach the devkit to the Raspberry Pi (use the USB/JTAG port or if you only have USB/UART, run espflash board-info).

$ probe-rs list
The following debug probes were found:
[0]: ESP JTAG -- 303a:1001:54:32:04:07:15:10 (EspJtag)

Maintenance

Updating (within the sandbox)

$ rustup update

Freeing disk space

The ~/target folder is used for all Cargo compilation caching (steered by ~/.cargo/config.toml). This folder may grow considerably large and is always safe to remove.

$ du -h -d 1 ~/target
1.6G	/home/ubuntu/target/release
247M	/home/ubuntu/target/thumbv7em-none-eabihf
783M	/home/ubuntu/target/debug
753M	/home/ubuntu/target/riscv32imac-unknown-none-elf
3.4G	/home/ubuntu/target

$ rm -rf ~/target

This helps you control the disk space use of the VM instance.

probe-rs-remote

~/bin/probe-rs-remote.sh and ~/bin/espflash-remote.sh scripts currently need manual care, if you wish to bring updates to them. Just copy-paste from the source:

$ curl https://raw.githubusercontent.com/lure23/probe-rs-remote/refs/heads/main/sh/probe-rs-remote.sh \
  -o ~/bin/probe-rs-remote.sh

$ curl https://raw.githubusercontent.com/lure23/probe-rs-remote/refs/heads/main/sh/espflash-remote.sh \
  -o ~/bin/espflash-remote.sh

What's not in the box

Once you have cargo and suitable toolchains installed, adding more tools is easy. Here are some examples that particular projects might ask you to add:

  • clang

    A compiler needed if projects contain C/C++ code. Install by:

     $ sudo apt install libclang-dev clang

  • bindgen CLI

    Generator for Rust/C interfaces. Install by:

     $ cargo install bindgen-cli

Next

$ multipass shell rust-emb