User's Manual

Chapter 17: Bluetooth I/O
142 APx500 User’s Manual
second. We recommend maintaining test levels above
–54 dBFS for meaningful results.
AVRCP
AVRCP is the “Audio/Video Remote Control Profile.”
This profile is used in conjunction with A2DP, and pro-
vides “transport” controls such as Play, Pause,
Reverse, Forward, etc.
Roles
Supported profile roles are “controller” and “target.”
Note: when APx is the target, AVRCP com-
mands are ignored.
More about Bluetooth SSP
(Secure Simple Pairing) Mode
SSP is required for devices using Bluetooth v 2.1 and
later. Bluetooth v 2.0 and earlier devices use Legacy
Pairing.
APx provides four SSP (Secure Simple Pairing) options.
You must choose the option that is appropriate for the
Bluetooth device you are testing.
Man-in-the-middle (MITM)
Man-in-the-middle or MITM is the term used in Blue-
tooth technology to refer to Secure Simple Pairing
mechanisms that require human interaction. One
device may display a PIN, for example, and the user
may be required to enter the same PIN using a key-
board on a second device. MITM methods add secu-
rity to the pairing process.
APx SSP Modes
Just Works
This mode is used in Bluetooth device relationships
that require little security, such as headsets. User
interaction is not required.
Numeric Comparison, Display Only
Some Bluetooth devices have only a display screen to
interact with a user; an example is a car kit (car ste-
reo head unit). Use this mode when APx is playing the
role of such a device.
A use case would be testing a smart phone. APx would
be an A2DP Sink, HFP with a display only (the car kit),
and the DUT would be the smart phone. The phone
would initiate pairing, and APx would display the PIN
transmitted from the phone. The user would confirm
(using a button on the phone) that the PIN displayed
in APx matched the PIN on the phone.
Numeric Comparison, Display+Buttons
Some Bluetooth devices have a display screen and
one or more buttons to interact with a user; the but-
ton may be used for a binary (Yes/No) response to a
query. An example is a smart phone. Use this mode
when APx is playing the role of such a device.
A use case would be testing a car kit. APx would be an
A2DP Source, HFP Hands-Free with a display and but-
tons (the smart phone), and the DUT would be the car
kit. APx would initiate pairing and transmit a PIN to the
DUT. The DUT would display the PIN, and the user
would confirm (using a button in the APx prompt dia-
log) that the PIN in the DUT display and the APx PIN
matched.
Numeric Comparison, Keyboard
Some Bluetooth devices have a numeric or alphanu-
meric keyboard to interact with the user. An example is
a computer used as an audio source, distributing
iTunes audio to a home entertainment system. Use
this mode when APx is playing the role of such a
device.
There are not obvious use cases in audio test for this
mode, which is include in APx for completeness. A
non-audio test use case would be pairing a Bluetooth
keyboard to a tablet computer. The computer would
display a PIN, and the user would enter a PIN (using
the keyboard) that matches the PIN on the tablet
screen.
Legacy Pairing
Bluetooth v2.1 and later devices (such as APx) are per-
mitted to use Legacy Pairing modes when pairing with
a Bluetooth v2.0 or earlier device.
Glossary of Bluetooth terms
These terms are used in the Audio Precision Blue-
tooth audio testing implementation.
A2DP
is the Advanced Audio Distribution Profile, with two
roles: source and sink. This profile supports higher
bit rate, higher performance stereo audio, with sam-
ple rates up to 48 kHz. The SBC codec is manda-
tory; codecs such as mp3, AAC, apt-X and others
are optionally supported.
AG
is the duplex Audio Gateway role, used in HFP and
HSP. AG is the node (such as a car kit) that medi-
ates between the user and the mobile phone.
apt-X
is an optional high-performance codec used in
A2DP.
AT command
is an audible signal used to control a device. AT
commands are a PSTN (Public Switched Telephone
Network) legacy.
AVRCP
is the “Audio/Video Remote Control Profile.” This
profile is used in conjunction with A2DP, and pro-