Update flake.nix to use latest Rust toolchain

.cargo/config.toml

@@ -1,8 +1,14 @@
 [target.thumbv6m-none-eabi]
-runner = "probe-rs run --chip RP2040"
+runner = "direnv exec . elf2uf2-rs -d"
+rustflags = [
+    "-C", "linker=rust-lld",
+    "-C", "link-arg=-Tlink.x",
+    "-C", "link-arg=-Tlink-rp.x",
+    "-C", "link-arg=-Tdefmt.x",
+]
 
 [build]
 target = "thumbv6m-none-eabi"
 
 [unstable]
-build-std = ["core", "alloc"]
+# build-std = ["core", "alloc"]

.run/Flash_Pico_W.run.xml

@@ -1,7 +1,9 @@
 <component name="ProjectRunConfigurationManager">
   <configuration default="false" name="Flash Pico W" type="CargoCommandRunConfiguration" factoryName="Cargo Command">
-    <option name="command" value="run --release" />
+    <option name="buildProfileId" value="release" />
+    <option name="command" value="run" />
     <option name="workingDirectory" value="file://$PROJECT_DIR$" />
+    <envs />
     <option name="emulateTerminal" value="true" />
     <option name="channel" value="DEFAULT" />
     <option name="requiredFeatures" value="true" />
@@ -9,7 +11,8 @@
     <option name="withSudo" value="false" />
     <option name="buildTarget" value="REMOTE" />
     <option name="backtrace" value="SHORT" />
-    <envs />
+    <option name="isRedirectInput" value="false" />
+    <option name="redirectInputPath" value="" />
     <method v="2" />
   </configuration>
-</component>
+</component>

Cargo.lock

@@ -181,6 +181,15 @@ dependencies = [
  "syn 2.0.117",
 ]
 
+[[package]]
+name = "cortex-m-semihosting"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c23234600452033cc77e4b761e740e02d2c4168e11dbf36ab14a0f58973592b0"
+dependencies = [
+ "cortex-m",
+]
+
 [[package]]
 name = "crc-any"
 version = "2.5.0"
@@ -329,6 +338,29 @@ dependencies = [
  "defmt 0.3.100",
 ]
 
+[[package]]
+name = "defmt-test"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1c1e67ff0e1c6b1a9540a1a3e04454658faacdd188c91987c444d56e469d7dea"
+dependencies = [
+ "cortex-m-rt",
+ "cortex-m-semihosting",
+ "defmt 0.3.100",
+ "defmt-test-macros",
+]
+
+[[package]]
+name = "defmt-test-macros"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fe5520fd36862f281c026abeaab153ebbc001717c29a9b8e5ba9704d8f3a879d"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.117",
+]
+
 [[package]]
 name = "diff"
 version = "0.1.13"
@@ -1368,6 +1400,7 @@ dependencies = [
  "cyw43-pio",
  "defmt 0.3.100",
  "defmt-rtt",
+ "defmt-test",
  "embassy-executor",
  "embassy-net",
  "embassy-rp",

Cargo.toml

@@ -18,5 +18,19 @@ cortex-m-rt = "0.7.5"
 panic-probe = { version = "0.3.2", features = ["print-defmt"] }
 defmt = "0.3.10"
 defmt-rtt = "0.4.1"
+defmt-test = "0.3.0"
 static_cell = "2.1.0"
 portable-atomic = { version = "1.11.0", features = ["critical-section"] }
+
+[lib]
+test = false
+harness = false
+
+[[bin]]
+name = "rusty-dog"
+test = false
+path = "src/main.rs"
+
+[[test]]
+name = "example_test"
+harness = false

Makefile

@@ -1,3 +1,23 @@
+DIRENV := $(shell command -v direnv 2> /dev/null)
+
+# If we have direnv and we're not already in the environment, re-exec via direnv
+ifdef DIRENV
+    ifeq ($(origin DIRENV_DIR), undefined)
+        # Ensure direnv is allowed
+        _ALLOW := $(shell direnv allow . > /dev/null 2>&1)
+        # Re-exec make via direnv
+        EXEC := direnv exec . $(MAKE)
+build run test clean flatpak-build:
+	@$(EXEC) $@
+    else
+        # We are already inside direnv, or direnv is not available
+        EXEC :=
+    endif
+else
+    EXEC :=
+endif
+
+ifndef EXEC
 build:
 	cargo build
 
@@ -10,10 +30,10 @@ test:
 clean:
 	cargo clean
 
-.PHONY: build run test clean
-
-
 # Flatpak build target
 .PHONY: flatpak-build
 flatpak-build:
 	flatpak-builder --force-clean build-flatpak flatpak/app.flatpak.json
+endif
+
+.PHONY: build run test clean

README.md

@@ -2,6 +2,18 @@
 
 This project is an embedded Rust application for the Raspberry Pi Pico W, utilizing the Embassy async framework.
 
+## Build Commands
+
+This project uses a `Makefile` to simplify common tasks. The `Makefile` is configured to automatically use `direnv` to load the Nix environment if `direnv` is installed on your system. This ensures that the correct Rust toolchain and dependencies are available even if you haven't manually run `nix develop` or `direnv allow`.
+
+| Command | Description |
+|---------|-------------|
+| `make build` | Build the project using `cargo build` |
+| `make run` | Run the project using `cargo run` |
+| `make test` | Run tests using `cargo test` |
+| `make clean` | Clean build artifacts |
+| `make flatpak-build` | Build the Flatpak package |
+
 ## LLM Agent Guidelines
 
 This project uses LLM agents for configuration and housekeeping. Please refer to [agents.md](agents.md) for the rules and guidelines governing their use.
@@ -92,10 +104,33 @@ flatpak run org.example.rustdevshell
 
 This project is configured for seamless flashing from the IDE or terminal.
 
+### Flashing via USB (BOOTSEL mode)
+
+If you don't have a physical debugger, you can flash the Pico W directly via USB using the BOOTSEL mode:
+
+1.  **Enter BOOTSEL Mode**: Hold the `BOOTSEL` button on your Pico W while plugging it into your computer's USB port. It should appear as a USB mass storage device.
+2.  **Flash and Run**: Run the following command (or use the IDE "Run" button):
+    ```bash
+    cargo run --release
+    ```
+    This project is configured to use `elf2uf2-rs`, which automatically detects the Pico W in BOOTSEL mode, converts the binary to UF2 format, and flashes it.
+
+### Troubleshooting: Flashing Issues
+
+If you encounter issues flashing via USB:
+1.  **Check BOOTSEL mode**: Ensure the Pico W is mounted as a USB drive.
+2.  **Udev Rules (Linux)**: You may need permissions to access the USB device.
+    -   Create a file named `/etc/udev/rules.d/99-pico.rules`.
+    -   Add: `SUBSYSTEMS=="usb", ATTRS{idVendor}=="2e8a", ATTRS{idProduct}=="0003", MODE="0666"`
+    -   Reload rules: `sudo udevadm control --reload` and `sudo udevadm trigger`.
+3.  **Cable**: Ensure you are using a data-sync USB cable, not just a charging cable.
+
 ### Flashing from IDE
 
 If you are using **RustRover** or **IntelliJ Rust**, you can use the "Flash Pico W" run configuration provided in the `.run` folder. Just select it from the run menu and click "Run".
 
+**Note:** The project is configured to use `direnv exec .` in `.cargo/config.toml` to ensure `elf2uf2-rs` is available. Ensure `direnv` is installed and allowed (`direnv allow`) on your system. For the best experience, we recommend installing the **direnv** plugin for your IDE.
+
 ### Flashing from Terminal
 
 You can flash the Pico W by running:
@@ -104,10 +139,10 @@ You can flash the Pico W by running:
 cargo run --release
 ```
 
-This uses `probe-rs` (configured in `.cargo/config.toml`) to flash and run the binary via a CMSIS-DAP debugger or similar.
+This uses `elf2uf2-rs` (configured in `.cargo/config.toml`) to flash the binary via the USB BOOTSEL mode.
 
-If you prefer to use the UF2 bootloader (dragging to the drive or using `elf2uf2-rs`), you can change the runner in `.cargo/config.toml` to:
-`runner = "elf2uf2-rs -d"`
+If you prefer to use a physical debugger (e.g. CMSIS-DAP), you can change the runner in `.cargo/config.toml` to:
+`runner = "direnv exec . probe-rs run --chip RP2040"`
 
 ## Testing & Development Features
 

flake.nix

@@ -44,7 +44,7 @@
         rustToolchain =
           with inputs.fenix.packages.${prev.stdenv.hostPlatform.system};
           combine (
-            with stable;
+            with latest;
             [
               clippy
               rustc

memory.x

@@ -0,0 +1,9 @@
+MEMORY
+{
+  /* FLASH and RAM lengths must match the RP2040 */
+  BOOT2 : ORIGIN = 0x10000000, LENGTH = 0x100
+  FLASH : ORIGIN = 0x10000100, LENGTH = 2048K - 0x100
+  RAM   : ORIGIN = 0x20000000, LENGTH = 256K
+  SCRATCH_A : ORIGIN = 0x20040000, LENGTH = 4K
+  SCRATCH_B : ORIGIN = 0x20041000, LENGTH = 4K
+}

shell.nix

@@ -8,6 +8,7 @@ pkgs.mkShell {
     pkgs.rustfmt
     pkgs.clippy
     pkgs.rust-analyzer
+    pkgs.gnumake
   ];
   shellHook = ''
     echo "[shell.nix] Legacy shell for Rust dev. Use 'nix develop' for full flake support."

src/lib.rs

@@ -0,0 +1,4 @@
+#![no_std]
+
+// Logic and hardware-independent code goes here.
+// This allows you to run `cargo test` on your host machine.

src/main.rs

@@ -1,3 +1,12 @@
-fn main() {
-    println!("Hello from Rust skeletal app. Edit src/main.rs to get started!");
+#![no_std]
+#![no_main]
+
+use defmt_rtt as _;
+use embassy_executor::Spawner;
+use embassy_rp as _;
+use panic_probe as _;
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    defmt::info!("Hello from the Pico W!");
 }

src/net/mod.rs

@@ -0,0 +1,2 @@
+mod mqtt;
+mod wifi;

tests/example_test.rs

@@ -0,0 +1,13 @@
+#![no_std]
+#![no_main]
+
+use defmt_rtt as _;
+use panic_probe as _;
+
+#[defmt_test::tests]
+mod tests {
+    #[test]
+    fn it_works() {
+        assert!(true);
+    }
+}

tests/sample_test.rs

@@ -1,4 +0,0 @@
-#[test]
-fn test_sample() {
-    assert_eq!(1, 1);
-}