DFU_DNLOAD request commands

AN3156

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DocID017068 Rev 4

Figure 7. Write Memory: Device side

5.2

Set Address Pointer command

The Set Address Pointer command is selected when wValue = 0 and the first byte of the

buffer sent by the host is 0x21. The buffer length should be 5 (the four remaining bytes are

the address bytes, LSB first (32-bit address format)).

The host sends a DFU_DNLOAD request with the above mentioned parameters to set the

address pointer value used for computing the start address for Read and Write memory

operations.

The STM32 receives bytes as follows:

After sending the Set Address Pointer command, the host has to send the

DFU_GETSTATUS request.

The Set AddressPointer command is effectively executed only when a DFU_GETSTATUS

request is issued by the host. If the status returned by the device is not dfuDNBUSY, then an

error has occurred.

A second DFU_GETSTATUS request is needed to check if the command has been correctly

executed. If the received address is wrong or unsupported, the device status is then (Status

= dfuERROR, State = errTARGET).

Byte 1:

0x21

- Set Address Pointer command

Byte 2:

A[7:0]

- LSB of the address pointer

Byte 3:

A[15:8]

- Second byte of the address pointer

Byte 4:

A[22:16] - Third byte of the address pointer

Byte 4:

A[31:23] - MSB of the address pointer