kws_infer — Keyword Spotting Inference Example¶

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¶

cd neuralspotx/examples/kws_infer
cmake -S . -B build/apollo510_evb -G Ninja \
  -DCMAKE_TOOLCHAIN_FILE=cmake/nsx/toolchains/arm-none-eabi-gcc.cmake \
  -DCMAKE_BUILD_TYPE=Release \
  -DNSX_BOARD=apollo510_evb
cmake --build build/apollo510_evb

Flash & View Output¶

JFlashLiteExe -device AP510NFA-CBR -if SWD -speed 4000 \
  build/apollo510_evb/kws_infer.bin -addr 0x00410000

JLinkSWOViewerCLExe -device AP510NFA-CBR -itmport 0 -swofreq 1000000

System Init¶

Uses nsx_system_init() with a modified development preset:

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 HeliaRT v1.7.0 prebuilt + NSX modules

Dependencies¶

ARM GCC 14.3 (arm-none-eabi-gcc)
HeliaRT v1.7.0 (release-with-logs variant, for profiler hooks)
NSX modules: nsx-core, nsx-power, nsx-pmu-armv8m, nsx-harness