DFU V2 CDC Loader Example

Source code path: example/dfu_v2/cdc/loader

Supported Platforms

• sf32lb52-lcd_n16r8_hcpu — SF32LB52X, 16MB NOR flash (n16r8).

Overview

This example is the DFU loader subprogram for the USB-CDC channel of DFU V2. It is flashed independently into the DFU_V2_LOADER partition; after the bootloader detects an update flag it jumps in here to receive the new firmware over USB-CDC, write it directly to the target partition, and optionally show the upgrade progress on screen.

Usage Instructions

This loader usually does not need a separate build: the CDC user application’s SConstruct pulls it in as a child project via AddDFU_CDC(SIFLI_SDK) (see tools/build/building.py), so building the user application also produces the loader firmware. It can also be built standalone.

Hardware Requirements

Before running this example, prepare:

• One development board supported by this example (Supported Platforms).

menuconfig Configuration

Key configuration of this example (enabled by default in proj.conf):

• CONFIG_USING_DFU_V2=y — enables the DFU V2 middleware.

• CONFIG_DFU_V2_USE_CDC_TRANSPORT=y — selects USB-CDC as the DFU transport.

• CONFIG_PKG_USING_CHERRYUSB=y / CONFIG_PKG_CHERRYUSB_DEVICE=y — enables the CherryUSB device stack.

• CONFIG_PKG_CHERRYUSB_DEVICE_MUSB_SIFLI=y — SiFli MUSB USB device controller driver.

• CONFIG_PKG_CHERRYUSB_DEVICE_CDC_ACM=y — CDC ACM device class.

• CONFIG_PKG_USING_LITTLEVGL2RTT=y / CONFIG_LVGL_V9=y — enables the LVGL (v9) upgrade UI; with these off the loader still performs the upgrade, just without the UI.

• CONFIG_PKG_SIFLI_MBEDTLS_BOOT=y — mbedTLS support needed for boot-time firmware verification.

Compilation and Flashing

To build the CDC user application (the loader is included automatically), switch to the user application project directory and run the scons command to compile:

> scons --board=sf32lb52-lcd_n16r8_hcpu -j8

To build this loader standalone, switch to this example project directory and run the scons command to compile:

> scons --board=sf32lb52-lcd_n16r8_hcpu -j8

Artifacts are placed under the matching build_<board> directory. For detailed compilation and download steps, please refer to the Quick Start Guide.

Expected Results

1. After flashing, the board runs the user application (the screen shows Ver: 1.0.9).

2. The PC sends the 4-byte trigger magic 0xAA 0x55 0xDF 0x00 to the user application over USB-CDC; the app replies with the ACK 0xAA 0x55 0xDF 0x01, then calls dfu_enter_dfu_mode() to write the update flag and reboot.

3. After the reboot the bootloader detects the update flag and jumps into this loader (DFU_V2_LOADER partition). In main() the loader first calls dfu_init() to bring up the middleware, then dfu_check_install() to handle any pending install, and waits for the USB-CDC connection.

4. The PC tool connects and streams the new firmware to the loader in chunks. The loader receives it via dfu_process() and writes it directly to the target partition; the on_dfu_event() callback feeds progress to the LVGL UI so the screen shows the percentage, and a success popup appears when all images are complete.

5. The loader finishes the install and reboots; the bootloader jumps back into the new user application. The changed version label on the screen confirms a successful upgrade.

For debugging, the cdc_dfu_info console command reports USB readiness and the current transfer progress.

Troubleshooting

Reference Documentation

Update History

Version	Date	Release Notes
0.0.1	06/2026	Initial version