User's Manual

Enhanced Class 1 Bluetooth v2.1 Module
User’s Guide
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CONN-GUIDE-BT740_v0.2
For example:
If one end has Display only, but the other end has keyboard only, then the negotiation results in one end
displaying a six digit passcode on the Display Only side, which is then required to be entered at the
keyboard only end.
If both ends have Display with Yes/No, then during the procedure both ends display a six digit passcode
which needs to be visually compared and then the Yes/No buttons are used to confirm that they match.
This provides for a one in a million probability that a MITM attach is successful.
To enable this new interaction with a user during pairing a new EVT_SIMPLE_PAIRING was defined.
8.15.1 Pair Initiate
This command initiates a pairing with a peer device which is assumed to be ready and waiting for a
pairing. If that device is compliant with v2.0 and older of the Bluetooth specification then a legacy pairing
results and the pincode pin[] in this message is used otherwise there is a simple pairing procedure.
Command Packet
Offset
Field
Value
Comments
0
LENGTH
28
Fixed
1
CHANNEL
0
Fixed
2
COMMAND
[CMD_ PAIR_INITIATE]
3
FLOW_IN
??
Runtime value
4
TIMEOUT
5..120
Pairing timeout in seconds
5..10
BDADDR[]
Nap[0,1]:Uap[2]:Lap[3,4,5]
Bluetooth addr of device to be paired
11..27
PIN[]
17 byte string array
Null Terminated Pin code String. Maximum pin
code length is 16.
Response Packet
Offset
Field
Value
Comments
0
LENGTH
5
Fixed
1
CHANNEL
0
Fixed
2
COMMAND
[CMD_ PAIR_INITIATE]
3
FLOW_OUT
??
Runtime value
4
STATUS
As appropriate
If pairing is successful, the event message EVT_LINK_KEY or EVT_LINK_KEY_EX sends to the host
before the response to close the procedure, as shown in the message sequence chart below.
Pair Initiate may fail if there are any existing open connections. The status byte in the response will have
an appropriate value.
8.15.1.1 Simple Secure Pairing ‘Just Works’
The message sequence diagram for ‘Just Works’ when the device has specified no I/O capability is as
follows: