DV-1 Digital Voice Module
The DV-1 is a small module containing
an AMBE-2020 Voice Audio Codec chip and some supporting components, as well
as an analog front-end which gives it the possibility to directly take audio
from a connected microphone, and to send audio to a connected headset or
loudspeaker.
Designed to be added to one of the DUTCH*Star products, it
has no intelligence of its own, it is just a slave device in a larger system,
although it would be possible to use the module within another, non-DUTCH*Star
project with some design- and programming effort.
The analog connection consists of two standard audio jacks-
one for MIC and PTT (3.5mm), and one for SPKR (2.5mm), as is commonly used by
Kenwood and other transceiver manufacturers for their speaker-microphones for
portable equipment.
The digital side consists of two single-row pin headers which
plug into sockets on the target device. One of these connectors (the rightmost
one in the picture above) is the main connector, carrying signals such as power,
SPI to control the AMBE chip, and I2C to control the analog frontend chip.
In the DM-1, the modem actually never
deals with the analog signals.. it just sends incoming DV data frames to the
AMBE for decompression, which in turn then sends the uncompressed PCM audio
frames to the analog codec for conversion to analog audio signals, which are fed
to either a small headphones-style speaker, or to an external loudspeaker
through a (small) audio amplifier. Likewise, analog audio from a connected
microphone is converted to digital PCM format by the codec, which in turn sends
it to the AMBE chip for compression. The AMBE chip then sends the compressed
frames to the modem for transmission.
However, some applications would also like
to control the path between the AMBE chip and the codec chip, for example a
device which just translates between compressed and uncompressed audio data
formats. Those devices can then make use of the second (optional) connector on
this module, which carries all signals related to the PCM data frames as well as
the analog audio signals. In this configuration, the module acts like two
submodules on a single PCB: one half is the AMBE-based compressor and
decompressor, and the other half handles the conversion between analog audio and
digital (uncompressed) PCM format.
These connectors, and how to use them, will be documented in
the manual, in case users want to add the module to their own projects.