Web Bluetooth DFU (Enhanced Fork)

This repository is a fork of the original web-bluetooth-dfu library, specifically enhanced to provide robust support for nRF52811 and nRF52833 devices. It introduces a modernized build system and critical stability fixes for production environments.

🚀 Key Improvements

• Modern Build System: Updated to esbuild and TypeScript 5, providing a streamlined development experience and better tree-shaking.
• Reliable Data Transfer:
  • Strict CRC Validation: Immediate termination on validation failure to prevent firmware corruption.
  • Packet Receipt Notifications (PRN): Full implementation of PRN intervals (Opcode 0x02) for flow control.
• GATT Stability: Integrated a GATT Mutex to serialize write operations, effectively eliminating "GATT operation already in progress" errors.
• Simplified Deployment: Generates a standalone dist/secure-dfu.js bundle including all dependencies (JSZip, CRC32), ready for direct browser usage.
• Advanced Progress Tracking: Events now provide granular feedback, reporting both "Sent" and "Validated" byte counts.
• Smart Speed: Automatic degradation of transfer parameters (MTU, PRN) to adapt to unstable connections.

Tested and verified on nRF52811 and nRF52833 using stock Nordic bootloaders.

⚡ Smart Speed & Reliability

This library includes a "Smart Speed" feature designed to maximize performance on modern devices while maintaining reliability on older or unstable connections.

How it works

By default, the library starts with aggressive settings:

• MTU (Packet Size): 100 bytes (up from the standard 20)
• PRN (Packet Receipt Notification): Disabled (0) or configured by user.

If enableSmartSpeed is set to true, the library monitors for transmission errors (GATT write failures or CRC mismatches). Upon encountering an error:

1. It retries the operation 3 times with the current settings to rule out transient glitches.
2. If errors persist, it degrades the MTU to the next safe tier: [100 -> 64 -> 32 -> 23].
3. If MTU is already at the minimum (23 bytes), it reduces the PRN interval (e.g., from 12 to 6, then 1) to ensure stricter flow control.

This allows the transfer to be fast by default but robust enough to finish even in difficult radio environments.

Usage

const dfu = new SecureDfu(crc32);

// Enable Smart Speed (Auto Mode)
dfu.enableSmartSpeed = true;

// Optional: Configure manual starting points
dfu.packetSize = 100; // Default is 100
dfu.packetReceiptNotification = 12;

// Or use a custom strategy callback
dfu.enableSmartSpeed = (error, currentPrn, currentMtu) => {
    console.warn(`DFU Error: ${error}. Degrading...`);
    // Return new settings or null to abort
    return {
        prn: Math.max(1, Math.floor(currentPrn / 2)),
        packetSize: 20
    };
};

Web Bluetooth DFU (Original Readme)

Update device firmware via Nordic's DFU protocols using Web Bluetooth.

Versions

Since version 12 of Nordic's SDK, the device firmware update protocol has changed to be made secure. The protocol can be seen here:

https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v12.0.0/lib_dfu_transport_ble.html

Earlier protocols were insecure, so it is recommended to use the secure protocol version in this package.

Features

• Supports continuation of failed transfers and skipping of any init packet if already valid
• Supports Buttonless DFU activation
• Uses ES6 syntax assuming that all JS engines supporting Web Bluetooth are also ES6 compatible
• Written with TypeScript to promote type safety

Live Example

This repo has a live web example of the secure DFU. Open this site in a Web Bluetooth enabled browser:

https://thib3113.github.io/web-bluetooth-dfu/

• Supports drag-and-drop or uploading of firmware packages
• Supports unzipping of the firmware package in-browser
• Supports multiple firmware images in a single package (softdevice, bootloader, application)

Prerequisites

• Node.js v18 or newer.
• A browser with Web Bluetooth support (Chrome, Edge, Opera).

Installation

npm install @thib3113/web-bluetooth-dfu

Building

If you are contributing or want to build the bundles yourself:

npm install
npm run build

The output will be in the dist/ folder.

Usage

In the Browser (CDN / Script Tag)

You can use the standalone bundle which includes all dependencies:

<script src="https://unpkg.com/@thib3113/web-bluetooth-dfu/dist/secure-dfu.js"></script>
<script>
    const dfu = new SecureDfu(); // No need to pass CRC32 anymore
    // ...
</script>

In a Module System (ESM / TypeScript)

import { SecureDfu, SecureDfuPackage } from '@thib3113/web-bluetooth-dfu';

Device Configuration

You will need a Nordic nRF51822, nRF52832 or nRF52840 development kit running the latest softdevice. Secure DFU supports softdevices from S130.

Softdevices can be found on Nordic's site:

• S130 (for nRF51)
• S132 (for nRF52)
• S140 (for nRF52)

Upon flashing the device will be in bootloader mode and ready to receive a DFU transfer.

Example packages to update can be found in the firmware folder.

Device Development

An excellent article exists with a walkthrough of using the device firmware update here:

https://devzone.nordicsemi.com/blogs/1085/getting-started-with-nordics-secure-dfu-bootloader/

tl;dr

J-LINK Interface Firmware

• Ensure device is running the J-LINK interface firmware available from Nordic

Download / Install

• Download Nordic SDK
• Install J-Link Software Package
• Install nRF5x Command Line Tools (includes nrfjprog)
• Install nrfutil: $ pip install nrfutil

Flashing SoftDevice

• Erase the chip: $ nrfjprog --family NRF52 --eraseall
• Grab the relevant softdevice from website (links above) or the SDK (components/softdevice/<SoftDevice>/hex)
• Flash the softdevice: $ nrfjprog --family NRF52 --program <softdevice.hex> --sectorerase --reset

Using Test DFU Bootloader

• Grab the relevant bootloader from the SDK (examples/dfu/bootloader_secure_ble/<chip>/hex)
• Flash the bootloader: $ nrfjprog --family NRF52 --program <bootloader.hex> --sectoranduicrerase --reset

Signing Keys

• Create a signing key: $ nrfutil keys generate private.key
• Generate the .c file for the key: $ nrfutil keys display --key pk --format code private.key --out_file dfu_public_key.c

Developing an Application

• Ensure you have a machine with relevant build tools such as gcc, linux is easiest
• Rebuild the bootloader with your new key (Update the Makefile to use your new key file)
• Flash the bootloader: $ nrfjprog --family NRF52 --program <bootloader.hex> --sectoranduicrerase --reset
• Build your application using your new key file

Building DFU Package

Refer to this document:

https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v13.0.0/ble_sdk_app_dfu_bootloader.html

e.g.:

$ nrfutil pkg generate --debug-mode --application <your_app.hex> --key-file private.key dfu_app.zip