AMBE-20x0™-HDK Development Board
User’s Manual
(Preliminary)
Page 18
DVSI Confidential Proprietary
Section 4 – Communication via Channel Interface
Communication via Channel Interface
Overview
AMBE-20x0™-HDK board has two RS-232 connections that provide communication to and from the
board. The top connector is the RS-232 channel interface that provides the compressed voice serial
data bit stream. The RS-232 Channel I / O is an asynchronous serial interface that uses a protocol
designed by DVSI. A real-time, full-duplex communication link can be established by connecting a cable
to this connector on both units.
The board can encode data from either the handset or 3.5mm stereo jack (Line In) connections. Which
ever source is used the analog speech signal is first digitized by the on-board A-to-D converter and then
processed by the encoder and converted into a Formatted Data bit stream This compressed bit stream
which contains the respective data bit stream (the data rate depends on the software setting) will be
output to the RS-232 interface.
The HDK Board Decodes the encoded data received from the RS-232 connection and then plays it back
through the 16-bit D-to-A converter to the handset or output jack. The encoder and decoder are fully
asynchronous.
Basic Operation
The AMBE-20x0™-HDK Development Board provides the ability to encode and decode speech at
compression rates between 2.0 kbps to 9.6 kbps. The HDK encodes analog speech input from the
handset or RCA jack input connections and decodes compressed voice data from the RS-232 interface.
Analog speech from the RCA jacks or handset is digitized by the on board PCM3500 A/D-D/A (The
PCM3500 has a master clock speed of 4.096 MHz. and is configured for an 8 kHz sampling frequency)
and then sent to the AMBE-2000™ where it gets encoded into compressed digital data. This data may
be output to the channel interface, or loopbacked to the RCA jacks or handset depending on the user
settings.
THE HDK provides two modes of operation. The default mode “HDK Mode” is where the HDK takes the
configuration setting from the onboard switch setting and processes incoming analog speech from either
the handset or RCA jack inputs. Once the incoming speech has been processed and encoded it is then
sent out via the RS-232 channel interface. The format of the serial output is explained below. The
other mode of operation is the AMBE-2000™ Mode” in this mode of operation the incoming speech is
handle the same but the format of the encoded data stream over the RS-232 interface contain the
complete packet structure as in the AMBE packet.
When the board is configured to use the RS-232 interface the AMBE-2000™ Formatted Data bit stream
is output to the PC and can be stored in a file. The file format for the encoded speech (BITFILE with a
.bit suffix) is 16 bit little endian.
The AMBE-20x0™-HDK Development Board can decode a previously generated BITFILE. When the
HDK receives compressed digital data from the BITFILE over the RS-232 channel interface it is
processed by the AMBE-2000™ Vocoder Chip decoder and synthesized into a digital speech signal that
is then converted into an analog signal using the onboard D-to-A and then sent to the handset / RCA
jacks. The encoder and decoder are fully asynchronous.
Digital Voice Systems, Inc.
The Speech Compression Specialists
Содержание AMBE-20X0 HDK
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