More about Bluetooth

Created on 2012-11-09 00:14:00



Bluetooth is a short-distance (a few meters) control, data, and audio communications wireless technology. Bluetooth replaces annoying wires in the user’s “personal area.”

Bluetooth uses low power, frequency-hopping radio in the 2.4 GHz band. Communication is two-way (for handshaking, metadata, etc); some profiles (HFP, for example) support duplex audio (both directions simultaneously); some profiles (A2DP) only simplex audio (one direction per connection).

Typical uses are mouse, keyboard, cell phone, headphones, 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.


Bluetooth Profiles

Bluetooth has about 30 “profiles” that describe the capabilities and/or current operating modes for Bluetooth 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 headphones 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 profiles. 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 relatively low-quality (voice communications) bi-directional audio profile that includes AT-type commands for phone use.
  • HSP (Head Set Profile)
    This is a simpler version of HFP, with the same audio quality but no AT commands.
  • AVRCP (Audio Video Remote Control Profile)
    This provides Play-Pause-Forward-Reverse “remote control” transport-type commands to control an audio source. This profile is typically used in conjunction with A2DP for personal audio player applications.


Steps in connecting APx to a Bluetooth device

There are 3 steps involved in setting up a connection between any Bluetooth devices. APx500 software provides more visibility and control of options for these communication steps than most DUTs.

  • Discovery
    Discovery scans the area and lists any Bluetooth devices that are not “undiscoverable” (hidden). Many devices are undiscoverable by default, and must be set to a discoverable mode through a switching sequence.
  • Pairing
    Pairing establishes a mutual, secure relationship between devices that have at least one compatible profile. Pairing is stored in non-volatile memory in each device. Devices can pair with more than one other device.
  • Connection
    Paired devices can connect using compatible profiles and roles. Connection enables exchange of audio or control data. Each device can connect with only one device at a time.