Data Sheet

October 2017 BNO080 Datasheet 1000-3927

Byte

Field

Length LSB

Length MSB

Channel

SeqNum

Figure 1-26: SHTP Header

Length

Bit 15 of the length field is used to indicate if a transfer is a continuation

of a previous transfer. Bits 14:0 are used to indicate the total number of

bytes in the cargo plus header, which may be spread over multiple

messages. The bytes in the header field are counted as part of the

length. A length of 65535 (0xFFFF) is reserved because a failed

peripheral can too easily produce 0xFFFF. Therefore, the largest cargo

that can be transported is 32766 minus the header bytes. The BNO080

does not support receiving fragmented messages but it does support

sending them.

Channel

The channel number of the cargo. Channel 0 is the command channel

and is used by the SHTP.

SeqNum

The sequence number of the cargo. The sequence number is a

monotonically incrementing number that increments once for each

cargo sent or cargo continuation sent. Each channel and each direction

has its own sequence number. The sequence number is used to detect

duplicate or missing cargoes and to associate segmented cargoes with

each other.

The length field allows a host to schedule the correct number of clocks to generate for reads over I

C and SPI.

The BNO080 supports partial reads if the host cannot accept all the bytes in one read, the length will be updated

on a subsequent read. So, for instance a host could read the first 4 bytes to determine the number of clocks to

generate and then repeat the read with the required number of clocks. The protocol is fully described in [2].

The BNO080 supports 6 channels:

• Channel 0: the SHTP command channel

• Channel 1: executable

• Channel 2: sensor hub control channel

• Channel 3: input sensor reports (non-wake, not gyroRV)

• Channel 4: wake input sensor reports (for sensors configured as wake up sensors)

• Channel 5: gyro rotation vector

The SHTP control channel provides information about the applications built into the BNO080 firmware image. The

BNO080 uses advertisements to publish the channel maps and the names of the built-in applications.

The executable channel allows the host to reset the BNO080 and provide details of its operating mode. Figure

1-27 provides details.