BR262PMEVK
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2
Table 1. BelaSigna R262 PROTOTYPING MODULE LSAD CONFIGURATION
Pin Name
Preset
Description
CLOCK_SEL (SPI_CLK/GPIO0)
7
Internal Clock
BOOT_SEL (SPI_CS/GPIO1)
4
Active Mode
Talk Distance Selectable between Close-talk and Far-talk
(5 cm – 500 cm)
CHAN_SEL (SPI_SERO/GPIO2)
3
Dual Output Noise Reduction
(Two Single-ended Analog Outputs)
Channel 0 as per BOOT_SEL “Start of Range” (Close-talk)
Channel 1 as per BOOT_SEL and ALPHA_SEL
ALPHA_SEL (SPI_SERI/GPIO3)
4
Mixer set 60% between Start and End of Range
Connecting the Prototyping Module
The analog output signals are available on AO0 (6),
AO1 (7), and GNDA (
−
). An optional momentary
push-button control can be connected between GP5 (5) and
GNDD (
−
) that can be used to swap the two processed
outputs between AO0 and AO1. The pinout for the module,
along with typical connections are illustrated in Figure 2.
The analog outputs of the device can be connected to your
system’s analog inputs as single-ended signals using AO0
and GNDA and/or AO1 and GNDA. If the module is
re-configured to output a mono, differential analog output
by changing the CHAN_SEL resistors R4 and R5, via I
2
C
commands, or by loading a custom application, you can
connect AO0 and AO1 to your system as a differential
analog signal.
NOTE: The analog output impedance is 3 k
W
and is intended to drive
a high-impedance (line-level) input, not speakers nor
headphones directly. Refer to the BelaSigna R262 datasheet
for more information on output stage characteristics.
You can also use the prototyping module as a digital
microphone replacement outputting a stereo DMIC signal
on test point GP4 (4), provided you supply an appropriate
DMIC clock signal on the CLK (8) test point and
re-configure the module’s CLOCK_SEL resistive divider to
match the provided clock frequency. Refer to the
BelaSigna R262 datasheet for more information.
Swap Channels
Analog GND
Analog Output 1
Analog Output 0
1.8 to 3.3 VDC
GND
Figure 2. BelaSigna R262 Prototyping Module Typical Connections
Operating the Prototyping Module
The default configuration of the prototyping module
provides the widest noise reduction adjustment range
(close-talk to far-talk) by selecting preset 4 on the
BOOT_SEL input, and is pre-configured to simultaneously
output two different algorithm tunings: a pure close-talk
output on AO0, and an output that is close-talk mixed 60%
towards far-talk on AO1. The processed outputs from these
two algorithm tunings are available as single-ended analog
outputs on AO0 – GNDA, and AO1 – GNDA. The
application will swap the output channels when GP5 is
momentarily pulled low. If a momentary push-button is
connected between GP5 and GNDD, pressing and releasing
this button will swap the two processed outputs between
AO0 and AO1.
Close-Talk
Close-talk mode aggressively filters noise and manages
gain to pick up speech within 5 to 10 cm from the
microphone array, effectively attenuating both speech and
noise that is farther away. This mode is suitable for mobile
handsets and radios where the speech source is very close to
the microphones and the noise level can be quite high; up to
90 dB SPL. Noise reduction performance in this mode
ranges from 20 to 30 dB SNR improvement (SNR
−
I),
depending on the type of noise.
