WebSerial / JavaScript implementation for FNIRSI - DPS-150

This is a simple implementation of the FNIRSI - DPS-150 protocol in JavaScript. It is intended to be used with the WebSerial API, which is currently only available in Chrome.

https://www.fnirsi.com/products/dps-150

FNIRSI - DPS-150

The FNIRSI - DPS-150 is a CNC power supply working with USB-PD.

This power supply can be controlled via USB. Officially, however, only software for Windows is provided.

Project File Structure

This project consists of the following main files and directories:

• dps-150.js
  JavaScript implementation of the FNIRSI DPS-150 protocol. Handles serial communication, command construction, and parsing.

• index.html
  The main web application interface. Provides the UI for interacting with the power supply via the browser.

• script.js
  Contains the frontend logic, including device connection, UI state management, and data visualization.

• worker.js
  Runs as a Web Worker to handle background serial communication and device control, using Comlink for messaging.

This structure separates protocol logic, UI, and background processing for maintainability and clarity.

---
config:
  theme: 'base'
  themeVariables:
    fontFamily: "Noto Sans"
    primaryColor: '#073359'
    primaryTextColor: '#fff'
    primaryBorderColor: '#333'
    lineColor: '#333'
    secondaryColor: '#006100'
    textColor: '#333'
---
sequenceDiagram
    actor User as User
    participant Frontend as Frontend (script.js)
    participant Worker as Worker (worker.js)
    participant Device as Device (DPS-150)

    User->>Frontend: UI operation (connect/get/set)
    Frontend->>Worker: Send command via Comlink
    Worker->>Device: Send command via Serial
    Device-->>Worker: Response data (Serial)
    Worker-->>Frontend: Response data via Comlink
    Frontend-->>User: Update UI / Show data

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Getting Started

To run this project locally, simply start a static file server in the project root. For example, using serve:

npx serve .

Then open the displayed local URL in Google Chrome.

Protocol

All of this is speculative and not accurate.

The protocol is via serial communication. The command has the following format for both input and output.

byte	description
0	start byte 0xf1 (out) or 0xf0 (in)
1	command
2	type
3	length of data
4-n	data
n	checksum

all float value is in little-endian format.

Command

byte	decimal	description
0xa1	161	get value
0xb0	176	?
0xb1	177	set value
0xc0	192	?
0xc1	193	connection?

Calculation of the checksum

checksum = (bytes[2] + bytes[3] ... bytes[n-1]) % 256