Add nix-shell

.envrc

@@ -0,0 +1 @@
+use nix

.gitignore

@@ -7,3 +7,4 @@
 /build
 *.DS_Store
 __pycache__
+/.direnv

shell.nix

@@ -0,0 +1,23 @@
+{ pkgs ? import <nixpkgs> { } }:
+
+with pkgs;
+
+let inherit (lib) ;
+in mkShell {
+  buildInputs = [
+    cmake
+    ninja
+    python3
+    ccache
+    dtc
+    dfu-util
+    gcc-arm-embedded
+    python38Packages.west
+    python38Packages.pyelftools
+  ];
+
+  shellHook = ''
+    export ZEPHYR_TOOLCHAIN_VARIANT=gnuarmemb
+    export GNUARMEMB_TOOLCHAIN_PATH=${pkgs.gcc-arm-embedded}
+  '';
+}