# Hello World

Minimal SWO printf loop to verify your toolchain, board connection, and viewer.

| Declared by the example author | Value |
| --- | --- |
| Tier | Basics |
| Status | `tested` |
| Capabilities | `swo`, `printf` |
| Boards tested | `apollo510_evb` |

Build it from a source checkout by name, because the positional app argument resolves
under `./examples`:

```bash
nsx build hello_world --board apollo510_evb
```

The rest of this page is the example's own README, from
[`examples/hello_world/`](https://github.com/AmbiqAI/neuralspotx/tree/main/examples/hello_world).

Minimal **nsx** application. Initializes the runtime core and prints a
message to SWO in a loop.

This is the recommended starting point for new users — it validates that
your toolchain, board connection, and SWO viewer are all working.

It is also a **multi-target** example: a single lean `nsx.yml` declares a
`targets:` block supporting both `apollo510_evb` (default) and
`apollo4p_blue_kxr_evb`. Each board resolves its own derived
`<board>_minimal` profile; both are recorded in one combined `nsx.lock`, so this
serves as the simplest cross-family proving ground (Apollo5 + Apollo4P).

## Build & Run

```bash
# Default board (apollo510_evb)
nsx configure --app-dir .
nsx build     --app-dir .
nsx flash     --app-dir .      # requires JLink + EVB
nsx view      --app-dir .      # opens SWO viewer

# Apollo4P Blue KXR EVB
nsx build     --app-dir . --board apollo4p_blue_kxr_evb
```

## Expected Output

The SWO viewer will print once per second:

```
Hello from nsx!
Hello from nsx!
Hello from nsx!
...
```

Messages repeat once per second.  If you see nothing, check:

1. Board is powered and connected via SWD (JLink)
2. `nsx flash` completed without errors
3. SWO pin is not remapped — the default EVB configuration works out of the box