Specifications
Bluegiga Technologies Oy
Page 41 of 64
9.1.6 Mono Operation
Mono operation is a single-channel operation of the stereo codec. The left channel represents the single mono
channel for audio in and audio out. In mono operation the right channel is the auxiliary mono channel that may
be used in dual mono channel operation. Dual mono feature is FW dependent and iWRAP does not generally
support it.
9.1.7 Side Tone
In some applications it is necessary to implement side tone. This involves feeding an attenuated version of the
microphone signal to the earpiece. The WT32i codec contains side tone circuitry to do this. There is no
iWRAP support for the side tone but the side tone is configurable through PS Keys. To implement a side tone,
either the PS setting has to be programmed for each module separately or ask for modules with custom FW
with appropriate settings.
The side tone hardware is configured through the following PS Keys:
PSKEY_SIDE_TONE_ENABLE
PSKEY_SIDE_TONE_GAIN
PSKEY_SIDE_TONE_AFTER_ADC
PSKEY_SIDE_TONE_AFTER_DAC
9.2 PCM Interface
The audio PCM interface supports continuous transmission and reception of PCM encoded audio data over
Bluetooth.
PCM is a standard method used to digitise audio, particularly voice, for transmission over digital
communication channels. Through its PCM interface, WT32i has hardware support for continual transmission
and reception of PCM data, so reducing processor overhead. WT32i offers a bidirectional digital audio
interface that routes directly into the baseband layer of the on-chip firmware. It does not pass through the HCI
protocol layer.
Hardware on WT32i allows the data to be sent to and received from a SCO connection.
Using HCI FW up to 3 SCO connections can be supported by the PCM interface at any one time. However
iWRAP supports only 1 SCO connection at a time.
WT32i can operate as the PCM interface master generating PCM_SYNC and PCM_CLK or as a PCM
interface slave accepting externally generated PCM_SYNC and PCM_CLK. WT32i is compatible with various
clock formats, including Long Frame Sync, Short Frame Sync and GCI timing environments.
WT32i supports 13-bit or 16-bit linear, 8-bit μ-law or A-law companded sample formats, and can receive and
transmit on any selection of 3 of the first four slots following PCM_SYNC. The PCM configuration options are
enabled by setting the PS Key PSKEY_PCM_CONFIG32. Please contact Bluegiga technical support for
details about the PCM configuration.
9.3 I2S Interface
The digital audio interface supports the industry standard formats for I
2
S, left-justified or righ justified. The
interface shares the same pins as the PCM interface, which means each audio bus is mutually exclusive in its
usage. The internal representation of audio samples within WT32i is 16-bit and data on SD_OUT is limited to
16-bit per channel.
WT32i is not capable of generating the master clock for I
2
S, so it can only be used as a master with a codec
that is capable of producing the master clock from the SCK.