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BTSnoop/Monitor protocol formats
Opcode definitions
New Index
Code: 0x0000
Parameters: Type (1 Octet
Bus (1 Octet)
BD_Addr (6 Octets)
Name (8 Octets)
This opcode indicates that a new controller instance with a
given index was added. With some protocols, like the TTY-based
one there is only a single supported controller, meaning the
index is implicitly 0.
Deleted Index
Code: 0x0001
This opcode indicates that the controller with a specific index
was removed.
Command Packet
Code: 0x0002
HCI command packet.
Event Packet
Code: 0x0003
HCI event packet.
ACL TX Packet
Code: 0x0004
Outgoing ACL packet.
ACL RX Packet
Code: 0x0005
Incoming ACL packet.
SCO TX Packet
Code: 0x0006
Outgoing SCO packet.
SCO RX Packet
Code: 0x0007
Incomnig SCO packet.
Open Index
Code: 0x0008
The HCI transport for the specified controller has been opened.
Close Index
Code: 0x0009
The HCI transport for the specified controller has been closed.
Index Information
Code: 0x000a
Parameters: BD_Addr (6 Octets)
Manufacturer (2 Octets)
Information about a specific controller.
Vendor Diagnostics
Code: 0x000b
Vendor diagnostic information.
System Note
Code: 0x000c
System note.
User Logging
Code: 0x000d
Parameters: Priority (1 Octet)
Ident_Length (1 Octet)
Ident (Ident_Length Octets)
User logging information.
TTY-based protocol
This section covers the protocol that can be parsed by btmon when
passing it the --tty parameter. The protocol is little endian, packet
based, and has the following header for each packet:
struct tty_hdr {
uint16_t data_len;
uint16_t opcode;
uint8_t flags;
uint8_t hdr_len;
uint8_t ext_hdr[0];
} __attribute__ ((packed));
The actual payload starts at ext_hdr + hdr_len and has the length of
data_len - 4 - hdr_len. Each field of the header is defined as follows:
This is the total length of the entire packet, excuding the
data_len field itself.
The BTSnoop opcode
Special flags for the packet. Currently no flags are defined.
Length of the extended header.
This is a sequence of header extension fields formatted as:
struct {
uint8_t type;
uint8_t value[length];
The length of the value is dependent on the type. Currently the
following types are defined:
Type Length Meaning
1 Command drops 1 byte Dropped HCI command packets
2 Event drops 1 byte Dropped HCI event packets
3 ACL TX drops 1 byte Dropped ACL TX packets
4 ACL RX drops 1 byte Dropped ACL RX packets
5 SCO TX drops 1 byte Dropped SCO TX packets
6 SCO RX drops 1 byte Dropped SCO RX packets
7 Other drops 1 byte Dropped other packets
8 32-bit timestamp 4 bytes Timestamp in 1/10th ms
The drops fields indicate the number of packets that the
implementation had to drop (e.g. due to lack of buffers) since
the last reported drop count.
The fields of the extended header must be sorted by increasing
type. This is essential so that unknown types can be ignored and
the parser can jump to processing the payload.