CYW4343X
11.7 A2DP
In this case, the stereo FM audio is encoded by the on-chip SBC encoder and transported as an A2DP link to a remote Bluetooth
device. Sampling rates of 48 kHz, 44.1 kHz, and 32 kHz joint stereo are supported. An A2DP lite stack is implemented in the
CYW4343X to support this use case, which eliminates the need to route the SBC-encoded audio back to the host to create the
A2DP packets.
11.8 Autotune and Search Algorithms
The CYW4343X supports a number of FM search and tune functions, allowing the host to implement many convenient user func-
tions by accessing the Broadcom FM stack.
■
Tune to Play—Allows the FM receiver to be programmed to a specific frequency.
■
Search for SNR > Threshold—Checks the power level of the available channel and the estimated SNR of the channel to
help achieve precise control of the expected sound quality for the selected FM channel. Specifically, the host can adjust its
SNR requirements to retrieve a signal with a specific sound quality, or adjust this to return the weakest channels.
■
Alternate Frequency Jump—Allows the FM receiver to automatically jump to an alternate FM channel that carries the same
information, but has a better SNR. For example, when traveling, a user may pass through a region where a number of
channels carry the same station. When the user passes from one area to the next, the FM receiver can automatically switch
to another channel with a stronger signal to spare the user from having to manually change the channel to continue listen-
ing to the same station.
11.9 Audio Features
A number of features are implemented in the CYW4343X to provide the best possible audio experience for the user.
■
Mono/Stereo Blend or Switch—The CYW4343X provides automatic control of the stereo or mono settings based on the FM
signal carrier-to-noise ratio (C/N). This feature is used to maintain the best possible audio SNR based on the FM channel
condition. Two modes of operation are supported:
❐
Blend: In this mode, fine control of stereo separation is used to achieve optimal audio quality over a wide range of input
C/N. The amount of separation is fully programmable. In Figure 40, the separation is programmed to maintain a mini-
mum 50 dB SNR across the blend range.
❐
Switch: In this mode, the audio switches from full stereo to full mono at a predetermined level to maintain optimal audio
quality. The stereo-to-mono switch point and the mono-to-stereo switch points are fully programmable to provide the
desired amount of audio SNR. In Figure 41, the switch point is programmed to switch to mono to maintain a 40 dB SNR.
Document No. 002-14797 Rev. *H
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