[M55M1] NPU Keyword Spotting Inference

Application	This example code uses M55M1 NPU to demonstrate machine learning keyword spotting on the Zephyr platform.
BSP Version	M55M1_Series_BSP_CMSIS_V3.01.003
Hardware	NuMaker-X-M55M1D

This example demonstrates one keyword spotting (KWS) inference application that recognizes the presence of a keyword in a recording on Nuvoton's Ethos-U NPU platform. Its source comes from Arm’s ML embedded evaluation kit/Keyword Spotting example, which has more information on the keyword spotting application.

This example mainly consists of:

• Recording audio clip through digital microphone (DMIC)
• Running keyword spotting inference using the TensorFlow Lite Micro framework and the Ethos-U NPU. This will involve three steps:
  • Preprocess recorded audio clip to specified input tensor format for inference.
  • Run keyword spotting inference.
  • Postprocess output tensor format usable by external applications.
    
  
  

This example runs a model DS-CNN Medium INT8 that has been downloaded from the Arm Model Zoo. Then this model is optimized using the Vela compiler to be runnable and accelerated on the Ethos-U NPU platform.

Vela takes a .tflite file as input and produces another .tflite file as output, where the operators supported by Ethos-U have been replaced by an Ethos-U custom operator. In an ideal case the complete model network would be replaced by a single Ethos-U custom operator.

You can download the sample code at EC_M55M1_Zephyr_ML_KWS_V1.00.