nRF51 SDK - S110 SoftDevice
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The Device Firmware Update (DFU) Service exposes necessary information to perform Device Firmware Updates on the device. This service is not a service defined by the Bluetooth SIG, but a proprietary service defined by Nordic Semiconductor to demonstrate a typical Device Firmware Update on an nRF51 device.
The DFU Service does not depend on any other services. Support for the following GATT sub-procedures is mandatory for this service:
The DFU GATT Service can operate only on Bluetooth low energy as transport.
The DFU Service does not define any new error codes for the Attribute Protocol. Data exchange is in little endian (LSB first) order.
This service is instantiated as a primary service in DFU mode.
The assigned service UUID is 0x1531 over proprietary base. See the following table for Nordic Semiconductor's UUID:
Description | Number base |
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Company identifier: | 0x0059 |
UUID base: | 0x23, 0xD1, 0xBC, 0xEA, 0x5F, 0x78, 0x23, 0x15, 0xDE, 0xEF, 0x12, 0x12, 0x00, 0x00, 0x00, 0x00 |
Service UUID start: | 0x1530 |
Characteristic UUID start: | 0x1531 |
The DFU Service exposes one instance of the characteristics listed in the following table. The service does not impose any security requirements.
Characteristic name | Requirement | Mandatory properties | Description |
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DFU Packet | M | WriteWithoutResponse | See DFU Packet. |
DFU Control Point | M | Write, Notify | See DFU Control Point. |
The UUID of the DFU Packet characteristic is 0x1532 over proprietary base.
This characteristic receives data for Device Firmware Updates as DFU packets. DFU packets can contain different types of data, depending to the Op Code that is written to the DFU Control Point before the DFU packet is transmitted.
The size of each packet must be between 1 and (ATT_MTU - 3) octets. Packets must be in little endian (LSB first) order.
The following table defines the format for a DFU packet:
Names | Field requirement | Format | Additional information |
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DFU Packet | Mandatory | uint8 | This field may be repeated up to a maximum of 20 times, which means that the maximum length of this characteristic is 20 bytes. |
(Minimum and maximum values are not applicable.)
After writing "Start DFU" (0x01) to the DFU Control Point, you must write the image size to the DFU Packet characteristic.
The image size must be written in the following format:
All lengths must be uint32. If a length is not present (for example, if only the SoftDevice is updated), the length should be given as 0. For example:
After writing "Initialize DFU Parameters" (0x02) to the DFU Control Point, you must write an init packet to the DFU Packet characteristic.
See Safety-checking the image for information about the format of the init packet.
After writing "Receive Firmware Image" (0x03) to the DFU Control Point, you must write packets containing image data to the DFU Packet characteristic.
The firmware image can be split up in multiple DFU packets. The full image is transferred by writing each fragment as DFU packet to the DFU Packet characteristic.
The UUID of the DFU Control Point characteristic is 0x1531 over proprietary base.
The DFU Control Point characteristic is used to control the state of the Device Firmware Update process. All DFU procedures are requested by writing to this characteristic. A response that marks the end of the procedure is received as a notification.
The following table shows control point procedure operation codes and the respective parameters:
Names | Field requirement | Format | Additional information | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Op Code | Mandatory | uint8 | Enumerations:
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Number of Packets Information: Parameter value for the Packet Receipt Notification Request Op Code | C1 | uint16 | Number of packets of firmware data to be received by the DFU target before sending a new Packet Receipt Notification (control point notification with Op Code = 7). If this value is 0, the packet receipt notification will be disabled by the DFU target. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Request Op Code Information: Parameter value for the Response Code Op Code | C2 | uint8 | Refer to the Op Code table above for additional information on the possible values for this field. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Response Value Information: C2: This field is mandatory for the Response Code Op Code. Otherwise, this field is excluded. | C2 | uint8 | Enumerations:
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Response Parameter Information: C2: This field is optional for the Response Code Op Code. Otherwise, this field is excluded. | C2 | variable | Note: The Response Parameter of the response to the control point is a variable length field to allow a list of different values defined by the service specification. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Number of Bytes of Firmware Image Received Information: C3: This field is present if the Op Code is 0x11 (Packet Receipt Notification). | C3 | uint32 | Number of bytes of firmware data (excluding the start and init data) received by the DFU target at the given point of time. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
DFU Image Type Information: C4: This field is present if the Op Code is 0x01 (Start DFU). This field is parsed as bit field where each bit that is set indicates the image transferred for the requested DFU. | C4 | uint8 | Enumerations:
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DFU Init Packet Information: C5: This field is present if the Op Code is 0x02 (Initialize DFU Parameters). | C5 | uint8 | Enumerations:
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If an Op Code is written to the DFU Control Point characteristic and the Client Characteristic Configuration Descriptors of either or both of the DFU Control Point or the DFU Status Report are not configured for notifications, the DFU target will return an error response. The Attribute Protocol Application error code of this response will be set to "Client Characteristic Configuration Descriptor Improperly Configured" (as defined in CSS Part B, Section 1.2 of Supplement to the Bluetooth Core Specification, Version 3 or later).