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DeviceScript supports simulation through a web dashboard and a Node.JS project running in parallel on the developer machine.

Simulated DeviceScript Device

DeviceScript will start a simulated programmable microcontroller on demand. You can also start it from the connect dialog. It runs a WASM-ed build of the C runtime.

A screenshot of starting the DeviceScript simulator


The simulators dashboard is the most convenient way to start simulating services and testing out your code.

  • Open the DeviceScript view in Visual Studio Code
  • Click on the dashboard icon in the Devices menu

A screenshot of the simulator view

Node.JS simulation

For advanced simulation scenario, you can use Node.JS and the TypeScript client library and, any other Node package (like your favorite test project), to generate complex scenarios.

Start by configuring your project for simulation by running

devs add sim

or in Visual Studio Code, using the DeviceScript: Add Sim... in the command palette.

  • all .ts files, expect for the ./sim/ folder, are compiled into DeviceScript bytecode
  • all file under ./sim/ are compiled as a Node.JS application
.devicescript/*  libraries and supporting files
src/main.ts DeviceScript entry point
sim/app.ts Node entry point for the simulator

Running using package scripts

The scripts in package.json are configured support both DeviceScript and sim build and watch.


# build DeviceScript and node.js sim
yarn build

# build device script only
yarn build:devicescript

# build node.js sim only
yarn build:sim


# watch DeviceScript and node.js sim
yarn watch

# watch device script only
yarn watch:devicescript

# watch node.js sim only
yarn watch:sim

Debugging DeviceScript and Node

Visual Studio Code supports multiple debugging sessions simultaneously so it is possible to debug your DeviceScript code and the simulator in the same session.

aurascope example

This simulator sample starts a simulated psychomagnotheric energy sensor (custom service) using jacdac-ts.

// Jacdac bus that will connect to the devtools server
import { bus } from "./runtime"
// Jacdac helper to simulate services
import { addServer, AnalogSensorServer } from "jacdac-ts"
// custom service
import { SRV_PSYCHOMAGNOTHERIC_ENERGY } from "../.devicescript/ts/constants"

// server for the custom service
const server = new AnalogSensorServer(SRV_PSYCHOMAGNOTHERIC_ENERGY, {
readingValues: [0.5],
readingError: [0.1],
streamingInterval: 500,
// change level randomly
setInterval(() => {
// randomly change the
const newValue = server.reading.values()[0] + (0.5 - Math.random()) / 10
console.debug(`psycho value: ${newValue}`)
}, 100)
addServer(bus, "aurascope", server)