The DFU device interface is enabled by default in the XMOS USB Audio framework (see devicedefines.h), and explicitly enabled in each reference design by the following line included in the customdefines.h file of each application:

#define DFU                (1)

Use the XMOS Development Tools to run the command:

xflash --boot-partition-size 0x30000 --factory usb_audio.xe

Where the size passed using the --boot-partition-size n argument specifies in bytes the minimum size required to store the boot loader, factory image and any upgrade images.

The following can be used as a guide to help calculate the required boot partition size for a design:

• boot partition size = loader size + maximum size of factory image + maximum size of upgrade images + padding to sector boundaries

Where:

• loader size = 0x1000 bytes, or 0x4000 bytes if secure boot functionality is used (for tools version 13.1.0 and older)
• maximum size of factory image = number of xCORE tiles * xCORE SRAM size
• maximum size of upgrade images = (number of xCORE tiles * xCORE SRAM size) * number of images to be held in flash concurrently

The above example sets the boot partition to a size appropriate for designs based on a single xCORE tile, where a single upgrade image is required in flash at any one time.

This programs the factory default firmware image into the flash device. The device will now support the DFU mechanism, and can use it to safely receive firmware updates, as well as revert to the factory firmware image when required, such as in the event of a failed upgrade attempt.

To use the firmware upgrade mechanism you need to build a firmware upgrade image:

1. Edit the customdefines.h file of the application for the hardware in use, and change the Device Version Number by defining BCD_DEVICE.
2. Rebuild the application.

To generate the firmware upgrade image run the following command:

xflash --factory-version 13 --upgrade 1 usb_audio.xe -o new_firmware.bin

Where the tools version passed using the --factory-version version argument specifies the version of the tools used to create the factory image. This should be passed as 12 for images created using tools versions 10, 11 and 12.

The --upgrade id xe-file [size] argument specifies xe-file as an upgrade image with version id. Each version number must be a unique number greater than 0.

You should now have the file new_firmware.bin which contains the firmware with the newly specified Device Version Number.

For further details of the DFU features included in the XMOS USB Audio framework and their configuration please see the Device Firmware Upgrade (DFU) and the Configuration Defines sections of the USB Audio Design Guide.

For further details on the use of XFLASH to create factory and upgrade firmware images please see the XFLASH Command-Line Manual section of the xTIMEcomposer User Guide.