Page 26 of 28
© Cambridge Silicon Radio Limited 2014
CS-310152-UGP1
www.csr.com
BlueC
or
e
A
D
K
3
.0
Subw
oo
fer
U
s
er
G
uide
5.7.1.1. Amplifiers That Do Not Support MUTE I/O
For amplifiers that do not support MUTE I/O lines, a digital mute is applied by the DSP application (where the lowest
possible gain is applied to the audio stream) as soon as the DSP application has been successfully loaded and
connected to the DAC.
When the amplifier has fully powered on, the digital mute is disabled and the correct volume applied. For amplifiers
that do not support MUTE I/O lines, the mute timer should be set to zero in the Application Features configuration,
see section 4.
5.7.1.2. Amplifiers That Support MUTE I/O
For amplifiers that support MUTE I/O lines, the digital mute is applied but the MUTE I/O line is also toggled
(depending on whether the MUTE I/O line is active high or active low) to put the external amplifier into MUTE mode.
When the DSP has successfully connected and is ready to stream data, the amplifier is un-muted by the MUTE I/O
line.
Only when the amplifier has entered UNMUTE mode and the audio system is active, is it considered safe for the
application to disconnect the audio stream again.
5.7.2. Disconnecting the Audio Stream
To ensure there is no disturbance when disconnecting an audio stream, the following procedure must be followed:
1.
Mute the amplifier
1.1.
Wait for the amplifier to mute
2.
Power off the amplifier
2.1.
Wait for the amplifier to power off
3.
Disconnect the DAC
3.1.
Wait for the DAC to fully power off
The ADK 3.0 Subwoofer should wait for the DAC to fully power off before allowing it to be powered on again. This is
in case where the audio is requested to be disconnected and reconnected immediately after, which can happen quite
often with this application when switching between low and standard latency SWAT media channels.
This ensures the audio system is in a safe state to turn on after being disconnected and powered off.
5.7.2.1. Amplifiers That Do Not Support MUTE I/O
For amplifiers that do not support MUTE I/O lines, a digital mute is applied by the DSP application (where the lowest
possible gain is applied to the audio stream), this process is unlikely to take more than 10 ms which CSR
recommends as the default configuration.
5.7.2.2. Amplifiers That Support MUTE I/O
For amplifiers that support MUTE I/O lines, a digital mute is applied by the DSP application (where the lowest
possible gain is applied to the audio stream), followed by pulling/driving the MUTE I/O line (depending on whether
the amplifier MUTE line is active high or active low).
The time it takes the amplifier to enable MUTE mode is dependent on the amplifier hardware, the timer is
configurable in the Application Features configuration, see section 4.
