Specifications

Windows Embedded Automotive 7 Deep Dive: Phone Core and Media Core 20
Layer
Function
eL2CAP
Provides enhanced error detection and flow control.
SDP
Gives devices the ability to discover what services other Bluetooth devices support and what
parameters to use to connect to them.
RFCOMM
Provides RS-232 serial port emulation, up to 60 simultaneous connections.
AVDTP
Applies point-to-point signaling over a connection-oriented L2CAP channel, which enables
Advanced Audio Distribution Profile (A2DP) streaming.
AVCTP
Used by Audio/Video Remote Control Profile (AVRCP) to transfer Audio/Video Control (AV/C)
commands via L2CAP.
The Windows Embedded Automotive 7 reference platform uses the CSR BlueCore4 Bluetooth
chipset, a single-chip Bluetooth v2.1+EDR system. Microsoft provides the following key elements
where the Bluetooth chip, HCI, and audio meet in the Bluetooth hardware implementation:
• Bluetooth chips route asynchronous connection-oriented (ACO) traffic via USB or a
UART, which allows SCO audio to be routed via USB or PCM. The Automotive 7
hardware reference platform demonstrates BlueCore4 connections via both pathways.
• Registry configuration for BlueCore4 can be found in the registry at
HKEY_LOCAL_MACHINE\Software\Microsoft\Bluetooth\Transports\PnP\{B3DD867A-
1E6E-4215-8AA7-EAC1DFC46548}
• BlueCore4 can also be configured by setting the PSKEYs
\public\autocomp\oak\drivers\Bluetooth\csr_pskeys.h. The power settings may require
adjustment for controller subsystem qualification.
• The Bluetooth Class of Device (COD) for any device developed for Automotive 7 can be
set in the registry, but the recommended default is
HKEY_LOCAL_MACHINE\Software\Microsoft\Bluetooth\sys, “COD"=dword:340408
Acoustic Echo Cancellation/Noise Suppression
Windows Embedded Automotive 7 includes support for acoustic echo cancellation/noise
suppression (AEC/NS), which removes noise and echo from voice communications. This
improves voice quality on phone calls. Automotive 7 meets Verband der Automobilindustrie
(VDA) standards for AEC/NS performance with the following attributes:
• Sending delay of 67.5 milliseconds (ms).
• Receiving delay of 57.62 ms (VDA standard is less than 120 ms).
• Echo delay of 125.12 ms (VDA standard is less than 260 ms).
Individual phones can have custom AEC/NS settings.
AEC/NS Configuration Registry Keys
AEC/NS is configured via three registry keys. The gain and audio processing registry key is
HKEY_LOCAL_MACHINE\Drivers\BuiltIn\Audio\AEC. This registry key provides two values that are a