User's Manual

Chapter 17: Bluetooth I/O
APx500 User’s Manual 141
example) support duplex audio (both directions simul-
taneously); some profiles (A2DP) support only simplex
audio (one direction per connection).
Typical uses are mouse, keyboard, cell phone, head-
phones, hands-free talk and listen.
APx Bluetooth Option
An APx Bluetooth Option module must be fitted in the
analyzer instrument to enable Bluetooth transmission
and reception. See Bluetooth Option on page 9.
Bluetooth Profiles
Bluetooth has about 30 “profiles” that describe the
capabilities and/or current operating modes for Blue-
tooth devices. For devices to communicate, they must
support and share a common profile.
For example, a wireless mouse uses the “HID” profile,
which has no audio capabilities. Wireless head-
phones use the “A2DP” profile, which has no cursor
control capabilities. The Bluetooth profiles these
devices use are not compatible with each other.
APx supported profiles
The APx Bluetooth Option supports four Bluetooth pro-
files. The supported profiles are
•A2DP (Advanced Audio Distribution Profile)
This is a one-way (source or sink), relatively high-
quality stereo audio profile.
•HFP (Hands Free Profile)
This is a bi-directional voice communications
audio profile that includes AT-type commands for
phone use. Legacy Bluetooth DUTs support only
the CSVD codec at sample rate of 8 kHz; HFP 1.6
compatible DUTs support the wideband voice
mSBC codec at a sample rate of 16 kHz.
•HSP (Head Set Profile)
This is a simpler version of HFP, using the CSVD
codec at 8 kHz and a reduced set of AT com-
mands.
•AVRCP (Audio Video Remote Control Profile)
This provides Play-Pause-Forward-Reverse
“remote control” transport-type commands to con-
trol an audio source. This profile is typically used in
conjunction with A2DP for personal audio player
applications.
More about Supported Bluetooth
Profiles
HSP
HSP is the “Head Set Profile.” This profile supports
voice-quality audio, using the CVSD codec at 8 kHz
sample rate. This profile is used for phone-to-headset
communication.
Roles
Supported roles are AG “Audio Gateway” (the phone)
and HS “Headset”.
Audio
Audio flows in a duplex (bi-directional) mode, connect-
ing the Audio Gateway device to the Headset device.
Actions
A subset of AT commands are also supported for
phone operations.
HFP
HFP is the “Hands Free Profile.” This profile supports
voice-quality audio, using the CVSD codec at 8 kHz
sample rate or the HFP 1.6 “wideband speech” mSBC
codec at 16 kHz*. This profile is used for phone-to-
headset communication and for phone-to-car kit
hands free communication.
*Note: HFP 1.6 wideband speech is only
available if the mSBC codec is supported by
your Bluetooth module hardware. See Blue-
tooth Option on page 9 for more informa-
tion.
Roles
Supported roles are AG “Audio Gateway” (the phone)
and HF “Hands Free” (the headset or car kit mic/
speaker).
Audio
Audio flows in a duplex (bi-directional) mode, connect-
ing the Audio Gateway device to the Hands Free
device.
Actions
A subset of AT commands are also supported for
phone operations. Compared to HSP, HFP provides a
few more AT commands for hands-free convenience,
such as last number redial.
A2DP
A2DP is the “Advanced Audio Distribution Profile.” This
profile supports higher bit rate, higher performance
stereo audio.
Roles
APx supported profile roles are “source” (transmitting
audio) and “sink” (receiving audio). Audio is distrib-
uted in one direction only, from the source device to
the sink device.
Audio
The SBC codec is mandatory; Audio Precision Blue-
tooth Options also support the aptX codec. The Blue-
tooth Duo option also supports aptX HD, aptX Low
Latency and AAC codecs. In A2DP Source, the APx
Bluetooth transmitter mutes the audio when the aver-
age signal level falls below –54 dBFS for more than 1