NeuralSPOT RPC Library

This directory contains RPC interfaces, NeuralSPOT wrappers for using those interfaces, and Python examples for creating PC-side applications that interact with those interfaces.

RPC (Remote Procedure Call) interfaces are a way to 'call' functions that reside on another CPU (in NeuralSPOT's case, on another computer entirely). NeuralSPOT RPC is based on a modified fork of EmbeddedRPC (eRPC) which supports RPC-over-TinyUSB on our EVBs. How eRPC works, including the specifics of IDL definition, is outside the scope of this document.

For example, this what the GenericDataOperations EVB-to-PC interaction looks like:

sequenceDiagram
    participant EVB
    participant PC
    note over EVB: client
    note over PC: server
    EVB->>+PC: ns_rpc_data_remotePrintOnPC(string)
    note right of PC: generic_data.py prints<br/> string on terminal;
    PC->>-EVB: ns_rpc_data_success;
    EVB->>+PC: ns_rpc_data_sendBlockToPC(&outBlock);
    Note right of PC: generic_data.py converts sample<br>  in dataBlock to WAV and <br/>appends to wav file;
    PC->>-EVB: ns_rpc_data_success
    EVB->>+PC: ns_rpc_data_computeOnPC(&outBlock, &resultBlock)
    Note right of PC: generic_data.py consumes <br/> dataBlock and returns mocked<br/> up resultBlock
    PC->>-EVB: ns_rpc_data_success

NS-RPC Directory Structure

ns-rpc/
    interfaces/ # contains IDL definition files
    includes-api/ # API for each interface
    python/ # PC-side code implementing the interface and example client/servers using it
    src/ # Code implementing the interface and wrapping it for neuralspot

Examples for using ns-rpc:

• Basic TF Stub
• Client Example
• Server Example

Guidelines for creating new interfaces or modifying existing interfaces can be found in our developer's guide.

Running generic_data.py for the first time

Our example RPC Python application, generic_data.py uses eRPC to communicate with the EVB. It can function in both client and server modes, and demonstrates how to capture both audio and MPU data.

This application requires several Python packages: 1. ERPC's Python library 2. PySerial to communicate with USB TTY devices 3. numpy to facilitate working with arrays 4. SoundFile to convert PCM data to WAV files

The simplest way to install these packages is using setup.py:

$> cd .../neuralSPOT
$> python setup.py install

Managing python and package versions is beyond the scope of this article - if you are using your PC to develop AI models it is likely you have your preferred setup. Otherwise, the simplest way to manage all of this is using a pre-package Python development environment such as Anaconda.

For bare-bones Windows Python configration, see our Windows application note.