add nixos shell

.envrc

@@ -0,0 +1 @@
+eval "$(lorri direnv)"

memory.x

@@ -1,6 +1,6 @@
 /* STM32F072CxT6 */
 MEMORY
 {
-  FLASH : ORIGIN = 0x08000000, LENGTH =  64K /* change length to 128K for STM32F072CBT6 */
+  FLASH : ORIGIN = 0x08000000, LENGTH =  128K /* change length to 128K for STM32F072CBT6 */
   RAM   : ORIGIN = 0x20000000, LENGTH =  16K
 }

rust-toolchain

@@ -0,0 +1,4 @@
+[toolchain]
+channel = "stable"
+components = [ "rust-src" ]
+targets = [ "thumbv6m-none-eabi" ]

shell.nix

@@ -0,0 +1,20 @@
+# Use nixpkgs with oxalica rust-bin overlay
+let
+  rust_overlay = import (builtins.fetchTarball
+    "https://github.com/oxalica/rust-overlay/archive/master.tar.gz");
+  nixpkgs = import <nixpkgs> { overlays = [ rust_overlay ]; };
+  rust_channel = nixpkgs.rust-bin.fromRustupToolchainFile ./rust-toolchain;
+in
+# Avoid typing `nixpkgs.` before each package name
+with nixpkgs;
+
+# Define the shell
+pkgs.mkShell {
+  buildInputs = [
+    dfu-util
+  ];
+
+  nativeBuildInputs = [
+    rust_channel # Full rust from overlay, includes cargo
+  ];
+}