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.

 

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