AN2662 DFU bootloader
Doc ID 14156 Rev 1 69/83
Note: The Detach request is not meaningful in the case of the bootloader. The bootloader is
started by a system reset depending on the boot mode configuration settings, which means
that no other application is running at this time.
Communication safety
The communication between Host and Device is secured by the embedded USB protection
mechanisms (CRC checking, Acknowledgements ...). No further protection is performed for
transferred data or for bootloader specific commands/data.
4.3 DFU bootloader commands
The DFU_DNLOAD and DFU_UPLOAD requests are mainly used to perform simple Write
Memory and Read Memory operations. They are also used to initiate the integrated
bootloader commands (write, read unprotect, erase, set address ...). The
DFU_GETSTATUS
command then triggers the command execution.
The selection of a command through the DFU download request is done through the wValue
parameter in the USB request structure. If wValue = 0 then the data sent by the Host after the request
is a bootloader command code. The first byte is the command code and the other bytes (if any) are the
data related to this command.
The selection of a command through the DFU upload request is done through the wValue
parameter in the USB request structure. If wValue = 0 then Get Command is selected and performed.
4.4 DFU_UPLOAD request commands
The upload request allows different commands to be performed. The command selection is
done through the value of
parameter wValue in the USB request structure. The operations
described in Section 4.4.1 to Section 4.5.5 are supported.
4.4.1 Read memory
The Read operation is selected when wValue > 1.
Table 6. Summary of DFU Class-Specific requests
bmRequest bRequest wValue wIndex wLength Data
00100001b DFU_DETACH wTimeout Interface Zero None
00100001b DFU_DNLOAD wBlockNum Interface Length Firmware
10100001b DFU_UPLOAD Zero Interface Length Firmware
00100001b DFU_GETSTATUS Zero Interface 6 Status
00100001b DFU_CLRSTATUS Zero Interface Zero None
00100001b DFU_GETSTATE Zero Interface 1 State
00100001b DFU_ABORT Zero Interface Zero None
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