MA300015 Microchip Technology, MA300015 Datasheet - Page 19

• Manufacturer Part Number: MA300015
• Description: MODULE PLUG-IN DSPIC30F 80QFP
• Manufacturer: Microchip Technology

Specifications of MA300015

• Accessory Type: Plug-in Module (PIM) - dsPIC30F6010A
• Peak Reflow Compatible (260 C): Yes
• Mcu Supported Families: DsPICDEM 1.1 Plus
• Leaded Process Compatible: Yes
• Supported Devices: DsPIC30F6010A
• Development Tool Type: Hardware - Daughter Card
• Silicon Manufacturer: Microchip
• Core Architecture: DsPIC
• Core Sub-architecture: DsPIC30
• Silicon Core Number: DsPIC30F
• Silicon Family Name: DsPIC30F6xxx
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: dsPICDEM Boards (DM300014 or DM300019)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

Summary
The dsPIC Digital Signal Controller (DSC) Acoustic Echo Cancellation (AEC)
Library provides a function to eliminate echo generated in the acoustic
path between a speaker and a microphone. This function is useful for
speech and telephony applications in which a speaker and a microphone
are located in close proximity to each other and are susceptible to signals
propagating from the speaker to the microphone resulting in a perceptible
and distracting echo effect at the far end. It is especially suitable for these
applications:
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For hands-free phones intended to be used in compact environments,
such as a car cabin, this library is fully compliant with the G.167 standard
for acoustic echo cancellation.
The AEC Library is written entirely in assembly language and is highly
optimized to make extensive use of the dsPIC DSC DSP instruction set
and advanced addressing modes. The algorithm avoids data overflow. The
AEC Library provides an “AcousticEchoCancellerInit” function for
initializing the various data structures required by the algorithm and an
“AcousticEchoCanceller” function to remove the echo component
from a 10 ms block of sampled 16-bit speech data. The user can easily
call both functions through a well-documented Application Programmer’s
Interface (API).
The “AcousticEchoCanceller” function is primarily a Time Domain
algorithm. The received far-end speech samples (typically received across
a communication channel such as a telephone line) are filtered using an
adaptive Finite Impulse Response (FIR) filter. The coefficients of this filter
are adapted using the Normalized Least Mean Square (NLMS) algorithm,
such that the filter closely models the acoustic path between the near-
end speaker and the near-end microphone (i.e., the path traversed by
the echo). Voice Activity Detection (VAD) and Double Talk Detection (DTD)
algorithms are used to avoid updating the filter coefficients when there
is no far-end speech and also when there is simultaneous speech from
both ends of the communication link (double talk). As a consequence,
the algorithm functions correctly even in the presence of full-duplex
communication. A Non-Linear Processor (NLP) algorithm is used to
eliminate residual echo.
This library uses an 8 kHz sampling rate. However, the library includes a
sample rate conversion function that ensures interoperability with libraries
designed for higher sampling rates (9.6 kHz, 11.05 kHz or 1 kHz). The
conversion function allows incoming signals at higher sampling rates to
be converted to a representative 8 kHz sample. Similarly, the conversion
function allows the output signal to be converted upward from 8 kHz to
match the user application.
Sample Rate Conversion
Computational requirements:
Program Flash memory:
RAM:
Note: The user application might require an additional  to .5 KB of RAM for
dsPIC® DSC
Acoustic Echo Cancellation Library
Length (ms)
Echo Tail
Hands-free cell phone kits
Speakerphones
Intercoms
Teleconferencing systems
data buffering (application-dependent).
64
3
16
MIPS
16.5
10.5
7.5
1 MIPS
.6 KB
0.5 KB
Program Flash
Memory (KB)
1
1
1
www.microchip.com
RAM
(KB)
5.7
3.4
.6
Devices Supported
dsPIC30F6014
dsPIC30F6014A
dsPIC30F601
dsPIC30F601A
Features
Key features of the Acoustic Echo Cancellation Library include:
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All functions can be called from either a C or Assembly application
program
Five user functions:
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Full compliance with the Microchip MPLAB® C30 C compiler,
assembler and linker
Simple user interface – one library file and one header file
Highly optimized assembly code, utilizing DSP instructions and
advanced addressing modes
Echo cancellation for 16, 3 or 64 ms echo delays or ‘tail lengths’
(configurable)
Fully tested for compliance with G.167 specifications for in-car
applications
Audio bandwidth: 0 to 4 kHz at 8 kHz sampling rate
Convergence rate: Up to 43 dB/sec., typically > 30 dB/sec.
Echo cancellation: Up to 50 dB; typically > 40 dB
Can be used together with the Noise Suppression (NS) Library, since
the same processing block size (10 ms) is used
dsPIC® DSC Acoustic Echo Cancellation Library User’s Guide included
Demo application source code is provided with the library
Accessory kit available for purchase includes an audio cable,
headset, oscillators, microphone, speaker, DB9 M/F RS-3 cable,
DB9M-DB9M null modem adapter and can be used for library
AcousticEchoCancellerInit
AcousticEchoCanceller
InitRateConverter
SRC_upConvert
SRC_downConvert
dsPIC30F5013 (for a max. of 3 ms echo delay)
dsPIC30F5011 (for a max. of 3 ms echo delay)
dsPIC33FXXXGPXXX
DS01033C-19