rsc-464 ETC-unknow, rsc-464 Datasheet - Page 22

• Manufacturer Part Number: rsc-464
• Description: Speech Recognition Processor
• Manufacturer: ETC-unknow

RSC-464
Because it is intended to “listen” continuously at very low power levels, the Audio Wakeup unit must detect each of
these events without any processor interaction. The processor configures and enables the unit under program
control before going into Idle mode. Audio Wakeup is not available in Sleep mode because the unit requires the
CLK2 signal. The detection signal from the Audio Wakeup unit can trigger a wakeup event, which starts the
processor and allows further audio processing. The processor inputs to the Audio Wakeup are an enable signal and
control signals to select for which sound to listen. See schematic 1-3 for details on this implementation.
The RSC-464 FluentChip™ library contains routines for detecting each of the four audio events listed above.
These routines also manage powerdown appropriately. See the “FluentChip™ Technology Library Manual” for
reference code to invoke these routines.
Microphones
A single electret microphone may be used both for the analog front-end input (for recognition purposes) and as the
sound source for the Audio Wakeup unit. The current consumption and frequency response requirements are
different for the two uses, so two microphone input pads are provided: MICIN1 for the normal recognition input to
the analog front-end, and MICIN2 for the Audio Wakeup analog front end. A common microphone ground is used
for both the normal recognition analog front-end and the Audio Wakeup analog front end.
During normal recognition and Audio Wakeup operation, the microphone would typically be powered from a source
with an impedance in the range of 1-3 Kohms. If both the normal recognition and Audio Wakeup front ends are
used, they must be isolated from each other by capacitors and may share one microphone and microphone bias
circuit. The switching of the microphone input source is under program control. See schematic 1-3 for details on
this implementation.
The recommended value for the microphone filter capacitor (labeled “C5” in Schematic 1-3) is in the range of
100uF-220uF. Using a capacitor at the upper end of this range will reduce low frequency noise. Low frequency
noise on the microphone input typically won’t affect recognition, but could affect the quality of speech playback
when using Record and Playback technology in an application. (see the “FluentChip™ Technology Library Manual”
for more information on Record and Playback) Typical low frequency noise sources include 60 Hz hum, “motor
22
NOTES:
1. Optional. This capacitor MAY reduce noise
coupled into the mic input on a noisy PCB.
2. If used, this capacitor MUST be placed
close to the RSC-4128 AGND and MIC1IN pads.
3. Place close to MICIN1.
4. Place close to MICIN2.
MICROPHONE
MK1
1
2
100 -> 220uF
R2
1.2K
example 1
C5
.1
C7
R1
AVdd
100
Px.n
.1
C6
NOTE 1
NOTE 2
MICROPHONE
3300pF
Example using one microphone for normal
operation only
(Px.n is any available port
I/O pin)
C8
NOTE 3
MK1
C1
.1
2.2uF
C2
1
2
Schematic 1-3
P/N 80-0282-A
RSC-4x
C3
1uF
.1
C4
100 -> 220uF
R2
1.2K
Vdd
C5
C8
.1
R1
100
.1
AVdd
C7
NOTE 1
NOTE 2
3300pF
Px.n
NOTE 4
.047
C6
Example using one microphone for
both Audio Wakeup and normal
operation
(Px.n is any available port
I/O pin)
C9
NOTE 3
2.2uF
C1
.1
C2
RSC-4x
Preliminary Data Sheet
© 2005 Sensory Inc.
.1
1uF
C4
C3
Vdd
AVdd
BT1
3V
Vdd