Boot Loader
DFU_UPLOAD This IN request is used to request a block of binary data from
the device. The data returned is device-specific but is typi-
cally the contents of a region of the device’s flash memory or
a device-specific response to a command previously sent via
a DFU_DNLOAD request. As with DFU_DNLOAD, the maximum
amount of data that can be requested is governed by the maxi-
mum packet size specified in the DFU functional descriptor, here
1024 bytes.
DFU_GETSTATUS This IN request allows the host to query the current status of the
DFU device. It is typically used during download operations to
determine when it is safe to send the next block of data. De-
pending upon the state of the DFU device, this request may also
trigger a state change. During download, for example, the de-
vice enters DNLOAD_SYNC state after receiving a block of data
and remains there until the data has been processed and a
DFU_GETSTATUS request is received at which point the state
changes to DNLOAD_IDLE.
DFU_CLRSTATUS This request is used to reset any error condition reported by
the DFU device. If an error is reported via the response to a
DFU_GETSTATUS request, that error condition is cleared when
this request is received and the device returns to IDLE state.
DFU_GETSTATE This IN request is used to query the current state of the device
without triggering any state change. The single byte of data re-
turned indicates the current state of the DFU device.
DFU_ABORT This request cancels any partially complete upload or download
operation and returns the device to IDLE state in preparation for
some other request.
2.3.3 Typical Firmware Download Sequence
The following flow chart illustrates a typical firmware image download sequence from the perspec-
tive of the host application.
14 April 8, 2013
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