# KWS Inference

TFLite Micro keyword-spotting inference with CMSIS-NN kernels.

| Declared by the example author | Value |
| --- | --- |
| Tier | Integrations |
| Status | `tested` |
| Capabilities | `ml`, `tflite`, `cmsis-nn`, `helia-rt` |
| Boards tested | `apollo510_evb` |

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

```bash
nsx build kws_infer --board apollo510_evb
```

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

End-to-end TFLite Micro inference demo on Apollo510, demonstrating:

- **nsx_system** modular init (one-call startup with preset config)
- **nsx_mem** memory placement (tensor arena in TCM, model weights in TCM)
- **NsxPmuProfiler** per-layer PMU profiling via TFLM's MicroProfilerInterface
- **ITM/SWO** printf output at 1 MHz via JLink

## Model

Google Speech Commands KWS (12-class): silence, unknown, yes, no, up, down,
left, right, on, off, stop, go.

- Input: `[1, 49, 10, 1]` int8
- Output: `[1, 12]` int8
- Ops: Conv2D, DepthwiseConv2D, AveragePool2D, FullyConnected, Reshape, Softmax
- Arena: ~20 KB of 64 KB allocated
- Inference: ~21 ms @ 192 MHz HP mode with I/D cache

## Build

```bash
cd neuralspotx/examples/kws_infer
nsx lock      --app-dir .
nsx configure --app-dir .
nsx build     --app-dir .
```

## Flash & View Output

```bash
nsx flash     --app-dir .
nsx view      --app-dir .
```

## System Init

Uses `nsx_system_init()` with a modified development preset:

```c
nsx_system_config_t cfg = nsx_system_development;
cfg.skip_bsp_init = true;   // skip BSP's 2-second delay
nsx_system_init(&cfg);       // → core, CPDLP, cache, HP mode, SpotMgr, ITM
```

This replaces ~60 lines of manual DCU/TPIU/ITM/cache/SpotManager init.

## Key Files

| File | Purpose |
|------|---------|
| `src/main.cc` | Application entry — system init, TFLM setup, inference loop |
| `src/kws_model_data.h` | Model weights as C array (in TCM via default .data) |
| `src/nsx_pmu_profiler.h` | Per-layer PMU profiler (TFLM MicroProfilerInterface) |
| `src/nsx_pmu_profiler.cc` | PMU profiler implementation — cycles, dcache misses, icache misses |
| `CMakeLists.txt` | Build config — links `nsx::helia_rt` source module + NSX modules |

## Dependencies

- ARM GCC 14.3 (`arm-none-eabi-gcc`)
- helia-rt (`nsx-helia-rt`) at the packaged registry pin, built from source (`release-with-logs` variant by default)
- ns-cmsis-nn (`nsx-cmsis-nn`) at the packaged registry pin, pulled in by `nsx-helia-rt`; `nsx.lock` records the exact tags
- NSX modules: `nsx-core`, `nsx-power`, `nsx-pmu-armv8m` (with the PMU API from the standalone module and the local SDK shim supplied by `nsx-ambiq-sdk`)