Datasheet

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4. Voice Subsystem
The integrated Voice Subsystem shown in the following figure is designed to support always-on voice capability and has
been optimized to work with Sensory TrulyHandsfree
™
Voice Control voice recognition software. The EOS S3 platform
supports two types of digital microphones. Both types of microphones are supported in mono and stereo configuration.
Figure 29: Voice Subsystem Block Diagram
STATUS_OUT
BufferInt
AP_PDM_CLK_STOPPED
AP_PDM_CLK_STARTED
BlockInt
WakeUpInt
PDM2PCM
Left
PDM2PCM
Right
Config/
Status
PDM_L
SRAM
DMAC
APB
Slave
CLK-DIV
Sensory
LPSD
Hardware
AHB_IF
HCLK
APB Interface
PDMCLK_SoC
PDM_IN_OUT
I2S_WD_CLK
Interface
Sampler
PDM_CKO
PDM_IN
I2S_CLK
I2S_DIN
Mode
Detection
STATUS_IN
AHB-Lite
Master
PDM_CKO_IN
PDM_R
SRAM
FIFO_1
SRAM
FIFO_0
SRAM
I2C
Interface
PDM Microphone
The EOS S3 platform supports PDM microphones in a mono or stereo configuration. As shown in the preceding figure,
the incoming PDM data is sampled using the PDM sampler. In case of a mono microphone, software can enable the Left
or Right PDM-to-PCM (PDM2PCM) converter. When two microphones are used in stereo configuration, both Left and Right
PDM2PCM converters are enabled. The output of the PDM2PCM converters are 16-bit PCM samples at a 16-kHz sample
rate. The PCM sample size and sample rate is chosen to support TrulyHandsfree Voice Control voice recognition software.
I
2
S Microphones
The EOS S3 platform also supports mono or stereo I
2
S microphones, as shown in the preceding figure. The I
2
S interface
inside the EOS S3 platform provides signals needed for interfacing to the microphones, and the outputs are 16-bit PCM
samples. The output can be used as is or it can be multiplied by a factor of 2, 4, or 8. In the case where down sampling of the
PCM sample is required, the PDM2PCM block can be used to down sample from a 32-kHz sample rate to a 16-kHz sample
rate. In situations where incoming PCM samples lack acoustic fidelity, digital gain of up to 34.5 dB can be applied to the