diff --git a/.github/dependabot.yaml b/.github/dependabot.yaml
new file mode 100644
index 0000000..d202a33
--- /dev/null
+++ b/.github/dependabot.yaml
@@ -0,0 +1,7 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      # Check for updates to GitHub Actions every week
+      interval: "weekly"
diff --git a/.github/workflows/build-attiny85.yaml b/.github/workflows/build-attiny85.yaml
new file mode 100644
index 0000000..6d18acf
--- /dev/null
+++ b/.github/workflows/build-attiny85.yaml
@@ -0,0 +1,47 @@
+name: Build ATtiny85
+
+"on":
+  pull_request:
+    branches: ["main"]
+    paths:
+      - .github/workflows/build-attiny85.yaml
+      - boards/attiny85/flake.lock
+      - boards/attiny85/flake.nix
+      - boards/attiny85/.cargo/**
+      - boards/attiny85/.justfile
+      - boards/attiny85/src/**
+      - boards/attiny85/avr-unknown-none-attiny85.json
+      - boards/attiny85/Cargo.lock
+      - boards/attiny85/Cargo.toml
+      - boards/attiny85/rust-toolchain.toml
+  push:
+    branches: ["main"]
+    paths:
+      - .github/workflows/build-attiny85.yaml
+      - boards/attiny85/flake.lock
+      - boards/attiny85/flake.nix
+      - boards/attiny85/.cargo/**
+      - boards/attiny85/.justfile
+      - boards/attiny85/src/**
+      - boards/attiny85/avr-unknown-none-attiny85.json
+      - boards/attiny85/Cargo.lock
+      - boards/attiny85/Cargo.toml
+      - boards/attiny85/rust-toolchain.toml
+  workflow_dispatch:
+
+jobs:
+  build-attiny85:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: DeterminateSystems/nix-installer-action@v14
+      - uses: DeterminateSystems/magic-nix-cache-action@v8
+      - name: Build
+        run: cd boards/attiny85; nix develop --command just build release
+      - name: Upload firmware
+        uses: actions/upload-artifact@v4
+        with:
+          name: attiny85-pwm-fan-controller
+          path: |
+            target/avr-unknown-none-attiny85/release/attiny85-pwm-fan-controller.elf
+            attiny85-pwm-fan-controller.hex
diff --git a/.github/workflows/cargo-lock-updater.yaml b/.github/workflows/cargo-lock-updater.yaml
new file mode 100644
index 0000000..f0fba4b
--- /dev/null
+++ b/.github/workflows/cargo-lock-updater.yaml
@@ -0,0 +1,30 @@
+name: Cargo Lock Updater
+
+"on":
+  schedule:
+    # Once a month on the 5th
+    - cron: "0 0 5 * *"
+  workflow_dispatch:
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  cargo-lock-updater:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: DeterminateSystems/nix-installer-action@v14
+      - uses: DeterminateSystems/magic-nix-cache-action@v8
+      - name: Update ATtiny85 Cargo lock file
+        run: cd boards/attiny85; nix develop --command cargo update
+      - name: Update Pico Cargo lock file
+        run: cd boards/pico; nix develop --command cargo update
+      - name: Create Pull Request
+        uses: peter-evans/create-pull-request@v7
+        with:
+          assignees: ${{ github.repository_owner }}
+          branch: "update/cargo-lock"
+          commit-message: "chore(deps): Update Cargo lock files"
+          title: "chore(deps): Update Cargo lock files"
diff --git a/.github/workflows/clippy-attiny85.yaml b/.github/workflows/clippy-attiny85.yaml
new file mode 100644
index 0000000..414fcdd
--- /dev/null
+++ b/.github/workflows/clippy-attiny85.yaml
@@ -0,0 +1,18 @@
+name: Lint Rust code with Clippy
+"on":
+  pull_request:
+    branches: ["main"]
+    paths:
+      - .github/workflows/clippy-attiny85.yaml
+      - boards/attiny85/flake.lock
+      - boards/attiny85/**.rs
+
+jobs:
+  clippy-attiny85:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: DeterminateSystems/nix-installer-action@v14
+      - uses: DeterminateSystems/magic-nix-cache-action@v8
+      - name: Lint Rust code with Clippy
+        run: cd boards/attiny85; nix develop --command cargo clippy
diff --git a/.github/workflows/flake-checker.yaml b/.github/workflows/flake-checker.yaml
new file mode 100644
index 0000000..e20dbbc
--- /dev/null
+++ b/.github/workflows/flake-checker.yaml
@@ -0,0 +1,14 @@
+name: Check Nix Flake
+"on":
+  pull_request:
+    branches: ["main"]
+    paths:
+      - .github/workflows/flake-checker.yaml
+      - '**/flake.lock'
+
+jobs:
+  flake-checker:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: DeterminateSystems/flake-checker-action@v9
diff --git a/.github/workflows/flake-lock-updater.yaml b/.github/workflows/flake-lock-updater.yaml
new file mode 100644
index 0000000..0530e11
--- /dev/null
+++ b/.github/workflows/flake-lock-updater.yaml
@@ -0,0 +1,25 @@
+name: Flake ❄️ Lock 🔒️ Updater ✨
+
+"on":
+  schedule:
+    # Pi o'clock
+    - cron: '3 14 * * 1,5'
+  workflow_dispatch:
+
+jobs:
+  lock-updater:
+    name: Flake Lock Updater
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - uses: DeterminateSystems/nix-installer-action@v14
+      - uses: DeterminateSystems/magic-nix-cache-action@v8
+      - uses: DeterminateSystems/update-flake-lock@v24
+        with:
+          pr-title: "chore: update flake.lock"
+          # Labels to be set on the PR
+          pr-labels: |
+            dependencies
+            automated
diff --git a/.github/workflows/format-just.yaml b/.github/workflows/format-just.yaml
new file mode 100644
index 0000000..f281a24
--- /dev/null
+++ b/.github/workflows/format-just.yaml
@@ -0,0 +1,19 @@
+name: Format justfiles
+"on":
+  pull_request:
+    branches: ["main"]
+    paths:
+      - .github/workflows/format-just.yaml
+      - '**/flake.lock'
+      - '**/.justfile'
+      - '**/justfile'
+
+jobs:
+  format-just:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: DeterminateSystems/nix-installer-action@v14
+      - uses: DeterminateSystems/magic-nix-cache-action@v8
+      - name: Format justfile
+        run: cd boards/attiny85; nix develop --command just --check --fmt --unstable ../..
diff --git a/.github/workflows/pre-commit-autoupdate.yaml b/.github/workflows/pre-commit-autoupdate.yaml
new file mode 100644
index 0000000..6c2fcef
--- /dev/null
+++ b/.github/workflows/pre-commit-autoupdate.yaml
@@ -0,0 +1,30 @@
+name: Pre-commit auto-update
+
+"on":
+  schedule:
+    # Once a month on the 2nd
+    - cron: "0 0 2 * *"
+  workflow_dispatch:
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  pre-commit-autoupdate:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: DeterminateSystems/nix-installer-action@v14
+      - uses: DeterminateSystems/magic-nix-cache-action@v8
+      - name: Update pre-commit hooks
+        run: nix develop --command pre-commit autoupdate
+      - name: Run pre-commit hooks
+        run: nix develop --command pre-commit run --all-files
+      - name: Create Pull Request
+        uses: peter-evans/create-pull-request@v7
+        with:
+          assignees: ${{ github.repository_owner }}
+          branch: "update/pre-commit-hooks"
+          commit-message: "chore(deps): Update pre-commit hooks"
+          title: "chore(deps): Update pre-commit hooks"
diff --git a/.github/workflows/rustfmt.yaml b/.github/workflows/rustfmt.yaml
new file mode 100644
index 0000000..5afe548
--- /dev/null
+++ b/.github/workflows/rustfmt.yaml
@@ -0,0 +1,18 @@
+name: Format Rust code
+"on":
+  pull_request:
+    branches: ["main"]
+    paths:
+      - .github/workflows/rustfmt.yaml
+      - '**/flake.lock'
+      - '**.rs'
+
+jobs:
+  rustfmt:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: DeterminateSystems/nix-installer-action@v14
+      - uses: DeterminateSystems/magic-nix-cache-action@v8
+      - name: Check Rust formatting
+        run: cd boards/attiny85; nix develop --command nu --commands 'rustfmt --check ../../**/*.rs'
diff --git a/.github/workflows/yamllint.yaml b/.github/workflows/yamllint.yaml
new file mode 100644
index 0000000..5812309
--- /dev/null
+++ b/.github/workflows/yamllint.yaml
@@ -0,0 +1,20 @@
+name: yamllint
+"on":
+  pull_request:
+    branches: ["main"]
+    paths:
+      - .github/workflows/yamllint.yaml
+      - .yamllint.yaml
+      - '**/flake.lock'
+      - '**.yaml'
+      - '**.yml'
+
+jobs:
+  yamllint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: DeterminateSystems/nix-installer-action@v14
+      - uses: DeterminateSystems/magic-nix-cache-action@v8
+      - name: Check YAML files
+        run: cd boards/attiny85; nix develop --command yamllint --format github ../..
diff --git a/.gitignore b/.gitignore
index 2825aa4..d574953 100644
--- a/.gitignore
+++ b/.gitignore
@@ -15,6 +15,13 @@ target/
 
 # Ignore any built binaries.
 *.bin
+*.hex
 
 *.jpg~
 *.jpg-autosave.kra
+
+# direnv
+.direnv/
+
+# Nix
+result/
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
new file mode 100644
index 0000000..9d4da43
--- /dev/null
+++ b/.pre-commit-config.yaml
@@ -0,0 +1,60 @@
+exclude: |
+  (?x)^(
+    .idea/.*|
+    .run/.*|
+    .vscode/.*
+  )$
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v4.6.0
+    hooks:
+      - id: check-byte-order-marker
+      - id: check-executables-have-shebangs
+      - id: check-json
+      - id: check-merge-conflict
+      - id: check-toml
+      - id: check-yaml
+        args: [--allow-multiple-documents]
+      - id: end-of-file-fixer
+      - id: mixed-line-ending
+      - id: pretty-format-json
+        args: ["--autofix"]
+        exclude: ^.vscode/.*\.json$
+      - id: trailing-whitespace
+  - repo: local
+    hooks:
+      - id: just
+        entry: just --fmt --unstable
+        files: |
+          (?x)^(
+            .justfile|
+            justfile
+          )$
+        language: system
+        name: just
+        pass_filenames: false
+      - id: rustfmt
+        name: rustfmt
+        description: Format Rust files with rustfmt.
+        entry: rustfmt
+        pass_filenames: true
+        types: [file, rust]
+        language: system
+      - id: rust-clippy-attiny85
+        name: Rust clippy ATtiny85
+        description: Run cargo clippy on files included in the commit.
+        entry: cargo -C boards/attiny85 clippy --all-targets --all-features -- -Dclippy::all
+        pass_filenames: false
+        types: [file, rust]
+        language: system
+      # - id: rust-clippy-pico
+      #   name: Rust clippy Pico
+      #   description: Run cargo clippy on files included in the commit.
+      #   entry: cargo -C boards/pico clippy --all-targets --all-features -- -Dclippy::all
+      #   pass_filenames: false
+      #   types: [file, rust]
+      #   language: system
+  - repo: https://github.com/adrienverge/yamllint.git
+    rev: v1.35.1
+    hooks:
+      - id: yamllint
diff --git a/.vscode/settings.json b/.vscode/settings.json
index 82d4499..daca860 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -6,16 +6,22 @@
         "Asciidoctor",
         "assumeyes",
         "attiny",
+        "autofix",
         "avrdude",
         "binutils",
         "BOOTSEL",
         "Boxall",
+        "clippy",
         "Datasheet",
+        "Dclippy",
         "devel",
+        "dialout",
         "eabi",
+        "getent",
         "ifdef",
         "ifndef",
         "ihex",
+        "justfile",
         "Libc",
         "libusbx",
         "microcontroller",
@@ -30,6 +36,7 @@
         "Pinouts",
         "proto",
         "Protoboard",
+        "rustfmt",
         "rustup",
         "SWCLK",
         "SWDIO",
@@ -38,6 +45,7 @@
         "tlsv",
         "UART",
         "udev",
+        "usermod",
         "VBUS"
     ]
 }
diff --git a/.yamllint.yaml b/.yamllint.yaml
new file mode 100644
index 0000000..d214411
--- /dev/null
+++ b/.yamllint.yaml
@@ -0,0 +1,6 @@
+extends: default
+
+rules:
+  document-start: disable
+  document-end: disable
+  line-length: disable
diff --git a/boards/attiny85/.cargo/config.toml b/boards/attiny85/.cargo/config.toml
index 30d224b..c9f46b1 100644
--- a/boards/attiny85/.cargo/config.toml
+++ b/boards/attiny85/.cargo/config.toml
@@ -1,9 +1,9 @@
 [build]
-target = "avr-specs/avr-attiny85.json"
+target = "avr-unknown-none-attiny85.json"
 
 #[target.'cfg(target_arch = "avr")']
 # ravedude doesn't support running from an AVR USB programmer like the USB uISP without code modifications.
-#runner = "ravedude trinket"
+# runner = "ravedude attiny85-usbtiny"
 
 [unstable]
 build-std = ["core"]
diff --git a/boards/attiny85/.envrc b/boards/attiny85/.envrc
new file mode 100644
index 0000000..3550a30
--- /dev/null
+++ b/boards/attiny85/.envrc
@@ -0,0 +1 @@
+use flake
diff --git a/boards/attiny85/.justfile b/boards/attiny85/.justfile
new file mode 100644
index 0000000..98aec62
--- /dev/null
+++ b/boards/attiny85/.justfile
@@ -0,0 +1,37 @@
+default: build
+
+alias fmt := format
+
+format: just-fmt rustfmt
+
+rustfmt:
+    cargo fmt
+
+just-fmt:
+    just --fmt --unstable
+
+alias b := build
+
+build profile="dev":
+    cargo build
+    cargo objcopy -- -O ihex attiny85-pwm-fan-controller.hex
+
+alias f := run
+alias flash := run
+alias r := run
+
+run profile="dev": (build profile)
+    avrdude -c USBtiny -B 4 -p attiny85 -U flash:w:attiny85-pwm-fan-controller.hex:i
+
+alias p := package
+alias pack := package
+
+package:
+    nix build
+
+alias u := update
+alias up := package
+
+update:
+    nix flake update
+    cargo update
diff --git a/boards/attiny85/README.adoc b/boards/attiny85/README.adoc
index f0e8cbb..354d2f7 100644
--- a/boards/attiny85/README.adoc
+++ b/boards/attiny85/README.adoc
@@ -20,6 +20,7 @@ endif::[]
 :fish: https://fishshell.com/[fish]
 :Git: https://git-scm.com/[Git]
 :Linux: https://www.linuxfoundation.org/[Linux]
+:Nix: https://nixos.org/[Nix]
 :Noctua-NF-P12-redux-1700-PWM-Fan: https://noctua.at/en/nf-p12-redux-1700-pwm[Noctua NF-P12 redux-1700 PWM Fan]
 :Python: https://www.python.org/[Python]
 :Rouge: https://rouge.jneen.net/[Rouge]
@@ -117,68 +118,65 @@ This should be the pin opposite the one attached to ground on the fan header.
 . Attach the USB µISP programmer to the 6-pin ISP breakout board.
 . Connect the 12V power supply to the 2nd pin in the fan header, the one immediately next to ground.
 
-== Program
+== Permissions
 
-. Install {rustup}.
+. On Fedora Atomic, the _dialout_ group does not exist in the `/etc/group`, so it must be added there.
 +
 [,sh]
 ----
-curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
+echo (getent group dialout) | sudo tee -a /etc/group
 ----
 
-. Install the AVR GCC toolchain, {AVR-Libc}, and {avrdude}.
+. Add the user to the _dialout_ group to access USB without requiring superuser privileges.
 +
 [,sh]
 ----
-sudo dnf --assumeyes install avr-gcc avr-libc avrdude
+sudo usermod --append --groups dialout $USER
 ----
 
-. Install {cargo-binutils}.
+. Create a udev rule to allow access to the USB µISP programmer without requiring root access.
 +
-[,sh]
+./etc/udev/rules.d/USBmicroISP.rules
+[,udev]
 ----
-cargo install cargo-binutils
+SUBSYSTEM=="usb", ATTR{product}=="USBmicroISP", ATTR{idProduct}=="0c9f", ATTRS{idVendor}=="1781", MODE="0660", GROUP="dialout"
 ----
 
-. Install the LLVM tools preview {Rust} component for cargo-binutils.
+. Reboot for the group change and Udev rules to take effect.
 +
 [,sh]
 ----
-rustup component add llvm-tools-preview
+sudo systemctl reboot
 ----
 
-. Clone the repository.
-+
-[,sh]
-----
-git clone https://github.com/jwillikers/pwm-fan-controller.git
-----
+== Develop
 
-. Change to the project's directory.
+. Install an implementation of {Nix}, such as https://lix.systems[Lix] used here.
 +
 [,sh]
 ----
-cd pwm-fan-controller/boards/attiny85
+curl -sSf -L https://install.lix.systems/lix | sh -s -- install
 ----
 
-. Build the executable.
+. Clone the repository.
 +
 [,sh]
 ----
-cargo build
+git clone https://github.com/jwillikers/pwm-fan-controller.git
 ----
 
-. Convert the executable to the file `pwm.hex` in the Intel hex format.
+. Change to the project's directory.
 +
 [,sh]
 ----
-cargo objcopy -- -O ihex pwm.hex
+cd pwm-fan-controller/boards/attiny85
 ----
-. Flash the `pwm.hex` file on the ATtiny85 with avrdude.
+
+. Build and flash the executable.
 +
 [,sh]
 ----
-avrdude -c USBtiny -B 4 -p attiny85 -U flash:w:pwm.hex:i
+nix develop --commands just flash
 ----
 
 == Todo
diff --git a/boards/attiny85/Ravedude.toml b/boards/attiny85/Ravedude.toml
new file mode 100644
index 0000000..ca17b9d
--- /dev/null
+++ b/boards/attiny85/Ravedude.toml
@@ -0,0 +1,10 @@
+[attiny85-usbtiny]
+name = "ATtiny85 through USBTiny"
+
+[attiny85-usbtiny.reset]
+automatic = true
+
+[attiny85-usbtiny.avrdude]
+programmer = "USBtiny"
+partno = "attiny85"
+bitclock = 4
diff --git a/boards/attiny85/avr-specs/avr-attiny85.json b/boards/attiny85/avr-unknown-none-attiny85.json
similarity index 89%
rename from boards/attiny85/avr-specs/avr-attiny85.json
rename to boards/attiny85/avr-unknown-none-attiny85.json
index d5334aa..da74364 100644
--- a/boards/attiny85/avr-specs/avr-attiny85.json
+++ b/boards/attiny85/avr-unknown-none-attiny85.json
@@ -37,5 +37,8 @@
   },
   "relocation-model": "static",
   "target-c-int-width": "16",
-  "target-pointer-width": "16"
+  "target-pointer-width": "16",
+  "target-family": "avr",
+  "vendor": "unknown",
+  "os": "none"
 }
diff --git a/boards/attiny85/default.nix b/boards/attiny85/default.nix
new file mode 100644
index 0000000..9f514dc
--- /dev/null
+++ b/boards/attiny85/default.nix
@@ -0,0 +1,63 @@
+# https://github.com/NixOS/nixpkgs/blob/master/pkgs/build-support/rust/build-rust-package/sysroot/default.nix
+{ stdenv
+, cargo-binutils
+, pkgs
+, rustToolchain
+# , rust-bin
+}:
+
+let
+  # rustToolchain = pkgs.pkgsBuildHost.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
+  rustPlatform = pkgs.makeRustPlatform {
+    rustc = rustToolchain;
+    cargo = rustToolchain;
+    # rustc = rust-bin.stable.latest.minimal;
+    # cargo = rust-bin.stable.latest.minimal;
+  };
+in
+rustPlatform.buildRustPackage {
+  pname = "attiny85-pwm-fan-controller";
+  version = "0.0.1";
+  src = ./.;
+  cargoLock = {
+    allowBuiltinFetchGit = true;
+    lockFile = ./Cargo.lock;
+  };
+  __internal_dontAddSysroot = true;
+  # useSysroot = false;
+  # env.CARGO_BUILD_TARGET = "${./avr-specs/avr-attiny85.json}";
+  # CARGO_BUILD_TARGET = "${./avr-specs/avr-attiny85.json}";
+  doCheck = false;
+  RUSTC_BOOTSTRAP = 1;
+  cargoExtraArgs = "-Z build-std=core";
+  # cargoExtraArgs = "--target avr-specs/avr-attiny85.json";
+  # postPatch = ''
+  #   ln -s ${./Cargo.lock} Cargo.lock
+  # '';
+  # buildPhase = ''
+  #   cargoBuildHook
+  # '';
+  # ${rust.envVars.setEnv} cargo cbuild -j $NIX_BUILD_CORES --release --frozen --prefix=${placeholder "out"} --target avr-specs/avr-attiny85.json
+  buildPhase = ''
+    runHook preBuild
+    cargo build -j $NIX_BUILD_CORES --release --frozen --target ${./avr-unknown-none-attiny85.json} -Z build-std=core
+    cargo objcopy -- -O ihex attiny85-pwm-fan-controller.hex
+    runHook postBuild
+  '';
+  postBuild = ''
+    cargo objcopy -- -O ihex attiny85-pwm-fan-controller.hex
+  '';
+  installPhase = ''
+    mkdir --parents $out/bin
+    mv attiny85-pwm-fan-controller.hex $out/bin/
+  '';
+  buildInputs = [
+  ];
+  nativeBuildInputs = [
+    # pkgs.buildPackages.stdenv.cc
+    cargo-binutils
+    # rust-bin.stable.latest.minimal
+    rustToolchain
+  ];
+  # auditable = false;
+}
diff --git a/boards/attiny85/flake.lock b/boards/attiny85/flake.lock
new file mode 100644
index 0000000..f94161e
--- /dev/null
+++ b/boards/attiny85/flake.lock
@@ -0,0 +1,82 @@
+{
+  "nodes": {
+    "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1726560853,
+        "narHash": "sha256-X6rJYSESBVr3hBoH0WbKE5KvhPU5bloyZ2L4K60/fPQ=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "c1dfcf08411b08f6b8615f7d8971a2bfa81d5e8a",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1727122398,
+        "narHash": "sha256-o8VBeCWHBxGd4kVMceIayf5GApqTavJbTa44Xcg5Rrk=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "30439d93eb8b19861ccbe3e581abf97bdc91b093",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs",
+        "rust-overlay": "rust-overlay"
+      }
+    },
+    "rust-overlay": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1727317727,
+        "narHash": "sha256-yGYahXzCquyYEgf5GTtvtaN5hXbw20Ok2+o8uVxoaFs=",
+        "owner": "oxalica",
+        "repo": "rust-overlay",
+        "rev": "a3d832f389606d7dc61a45b244c72ea472d1fcd4",
+        "type": "github"
+      },
+      "original": {
+        "owner": "oxalica",
+        "repo": "rust-overlay",
+        "type": "github"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/boards/attiny85/flake.nix b/boards/attiny85/flake.nix
new file mode 100644
index 0000000..18c5805
--- /dev/null
+++ b/boards/attiny85/flake.nix
@@ -0,0 +1,153 @@
+# https://github.com/NixOS/nixpkgs/blob/master/doc/languages-frameworks/rust.section.md
+# https://github.com/oxalica/rust-overlay
+# https://github.com/oxalica/rust-overlay/blob/660018f3a78e1f83e4e4aa569d9c6e2a31b0222c/docs/cross_compilation.md
+# https://github.com/oxalica/rust-overlay/issues?q=is%3Aissue+callPackage+is%3Aclosed
+# https://github.com/ipetkov/crane/blob/master/examples/cross-rust-overlay/flake.nix
+# https://github.com/alekseysidorov/nixpkgs-rust-service-example/blob/main/flake.nix
+# https://github.com/nix-community/naersk/blob/ee7edec50b49ab6d69b06d62f1de554efccb1ccd/examples/static-musl/flake.nix
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+    rust-overlay = {
+      url = "github:oxalica/rust-overlay";
+      inputs = {
+        nixpkgs.follows = "nixpkgs";
+        flake-utils.follows = "flake-utils";
+      };
+    };
+  };
+  outputs = { self, nixpkgs, flake-utils, rust-overlay }:
+    flake-utils.lib.eachDefaultSystem
+      (system:
+         let
+          overlays = [
+            (import rust-overlay)
+            # (self: super: {
+            #   pkg = super.pkg.overrideAttrs (old: {
+            #     doCheck = false;
+            #   });
+            # })
+          ];
+          pkgs = import nixpkgs {
+            inherit system overlays;
+          };
+          # todo Try creating toolchain from avrCrossPkgs.
+          rustToolchain = pkgs.pkgsBuildHost.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
+
+          avrCrossPkgs = import nixpkgs {
+            inherit system overlays;
+            crossSystem = {
+              inherit overlays;
+              config = "avr";
+              # rust.rustcTarget = "${./avr-specs/avr-attiny85.json}";
+
+              # todo I can try this one next.
+              # rust.rustcTarget = "avr-unknown-none-attiny85";
+              # rust.rustcTargetSpec = "avr-unknown-none-attiny85.json";
+              # rust.rustcTarget = "avr-unknown-gnu-atmega328";
+              # rust.rustcTargetSpec = "${./avr-unknown-none-attiny85.json}";
+              # rust.platform = nixpkgs.lib.importJSON "${./avr-specs/avr-unknown-none-attiny85.json}";
+              # rust.cargoShortTarget
+              # rust.cargoEnvVarTarget
+              rust.isNoStdTarget = true;
+
+              # rust.rustcTargetSpec = nixpkgs.lib.importJSON "${./avr-specs/avr-attiny85.json}";
+
+              # todo And maybe I need to try this too?
+              # rustc = {
+              #   config = "${./avr-unknown-none-attiny85.json}";
+              # };
+
+              # rust.rustcTarget = "avr-unknown-none";
+
+            #   rust.platform = {
+            #     arch = "avr";
+            #     atomic-cas = false;
+            #     cpu = "attiny85";
+            #     crt-objects-fallback = false;
+            #     data-layout = "e-P1-p:16:8-i8:8-i16:8-i32:8-i64:8-f32:8-f64:8-n8-a:8";
+            #     eh-frame-header = false;
+            #     exe-suffix = ".elf";
+            #     late-link-args = {
+            #       gnu-cc = [
+            #         "-lgcc"
+            #       ];
+            #       gnu-lld-cc = [
+            #         "-lgcc"
+            #       ];
+            #     };
+            #     linker = "avr-gcc";
+            #     linker-flavor = "gnu-cc";
+            #     llvm-target = "avr-unknown-unknown";
+            #     max-atomic-width = 8;
+            #     metadata = {
+            #       description = null;
+            #       host_tools = null;
+            #       std = null;
+            #       tier = null;
+            #     };
+            #     no-default-libraries = false;
+            #     pre-link-args = {
+            #       gnu-cc = [
+            #         "-mmcu=attiny85"
+            #         "-Wl,--as-needed,--print-memory-usage"
+            #       ];
+            #       gnu-lld-cc = [
+            #         "-mmcu=attiny85"
+            #         "-Wl,--as-needed,--print-memory-usage"
+            #       ];
+            #     };
+            #     relocation-model = "static";
+            #     target-c-int-width = 16;
+            #     target-pointer-width = 16;
+            #     target-family = "avr";
+            #     vendor = "unknown";
+            #     os = "none";
+            #   };
+            };
+            config.allowUnsupportedSystem = true;
+          };
+          # todo This should be using avrCrossPkgs for the Rust toolchain, right?
+          # rust-bin = rust-overlay.lib.mkRustBin { } avrCrossPkgs.buildPackages;
+          # rustToolchain = avrCrossPkgs.pkgsBuildHost.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
+          # rustToolchain = rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
+          nativeBuildInputs = with pkgs; [
+            avrdude
+            cargo-binutils
+            clippy
+            # ravedude
+            rustfmt
+            rustToolchain
+            fish
+            just
+            nushell
+            pkgconf
+            pre-commit
+            yamllint
+          ];
+          buildInputs = with pkgs; [];
+        in
+        {
+          packages.default = avrCrossPkgs.callPackage ./default.nix {
+            inherit rustToolchain;
+            # inherit rust-bin;
+          };
+          devShells.default = avrCrossPkgs.mkShell {
+            inherit nativeBuildInputs buildInputs;
+          };
+          apps.default = let
+            flash = pkgs.writeShellApplication {
+              name = "flash-attiny85-pwm-fan-controller";
+              runtimeInputs = [pkgs.avrdude];
+              text = ''
+                avrdude -c USBtiny -B 4 -p attiny85 -U flash:w:${self.packages.default}/bin/attiny85-pwm-fan-controller.hex:i
+              '';
+            };
+          in {
+            type = "app";
+            program = "${flash}/bin/flash-attiny85-pwm-fan-controller";
+          };
+        }
+      );
+}
diff --git a/boards/attiny85/rust-toolchain.toml b/boards/attiny85/rust-toolchain.toml
index 3523320..462b0a0 100644
--- a/boards/attiny85/rust-toolchain.toml
+++ b/boards/attiny85/rust-toolchain.toml
@@ -1,4 +1,4 @@
 [toolchain]
 channel = "nightly-2024-03-22"
-components = ["rust-src"]
+components = ["llvm-tools-preview", "rust-src"]
 profile = "minimal"