Index

[Index] [Description] [Operation] [DECT API] [Hardware] [Purchase] [Downloads] [FAQ] [Change Log]


Description

The DECT Shield allows Arduino boards to use DECT tecnology to communicate wirelessly with other DECT Shields or compatible DECT devices. The shield supports native voice and audio communications, and also data transmission at low rates up to 1 kb/s. An on-board microSD card slot allows the shield to reproduce and stream audio files, and it can be used by the Arduino. The DECT Shield provides the resources necessary to create applications where native audio transmission is necessary, such as wireless speakers or intercommunication devices.

DECT is the second most successfully ETSI standard after GSM, dominating the wireless voice application market with a share of 73%. It was created primarily for cordless phone systems in Small Office/Home Office (SOHO) applications, but currently it is also used in a wide variety of voice and data applications, such as baby monitors and traffic lights. DECT standard ensures high quality voice transmission without interference up to 100 meters of distance (no obstacles), not using the highly congested 2.4 GHz spectrum, but the licensed 1.8 GHz band.

The main motivation behind this project was the lack of low-cost DECT development resources and materials. Although there are a variety of DECT capable devices, there is not an economic and easy way to interact with them. The DECT Shield tries to solve this problem by bringing DECT to the general public.


Operation

DECT works in star topology as a micro-cell system. A simple cell is formed by a base station (FP - Fixed Part) and multiple portable terminals or handhelds, PPs (Portable Parts). A common home DECT telephone is composed of a single base station and a handheld, as illustrated bellow for example. The portable terminals must be registered to the basestation in order to establish communications.

DECT Components

The DECT Shield can operate as a handheld or a basestation, but not at the same time. A dual firmware system in the shield allows to switch operation during runtime, but it is not recomended since registration information will become invalid. Communications will not be possible until a new registration is executed. The DECT API library includes a sketch to help in the registration process between shields.


DECT API

The DECT API library is used with the Arduino to interact with the DECT Shield. The full documentation and reference can be consulted online here.

The current library version (1.0) contains three examples and two utility sketches. All sketches were tested using PuTTy at 9600bps and not with the included serial terminal in the Arduino IDE. The description of each sketch follows:

It is highly recommended to use the ConfigUtil when using a new shield for the first time or after a firmware change.


Hardware

The DECT Shield communicates with the Arduino through the dedicated SPI bus using pins 10 to 13 and pin 9 for selection. The microSD card shares the same bus, but uses pin 10 for selection. Pin 8 is reserved for Arduino-shield synchronization and cannot be used. Optionally, the shield can be configured to use external interrupt pin 2 in order to generate asynchronous events when something important is triggered.

Although the SPI bus is shared among the DECT components and the microSD card, it can be used to communicate with other devices even if there is a file playing in the shield. The shield disconnects the SPI bus from the Arduino in order to avoid data collisions.

The shield uses 3.3V provided by an on-board LDO and power is drawn from the Arduino regulated +5V pin. The table below shows the average shield current consumption for several situations.

Mode of Operation Portable Parte (mA) Fixed part (mA)
Idle 9.5 21.0
Voice communication (w/o loudpseaker) 24.0 33.5
Voice communication (w/ loudspeaker) 55.5 64.0
Data transmission 19.5 31.0
File reproduction (w/o loudspeaker) N/A 24.5

Purchase

A fully functional DECT Shield or a standalone Bithium DECT Module with a preloaded firmware can be purchase directly from Bithium. Please check the contact information in their official website.


Downloads

All downloads are for DECT Shield revision B:

C DECT API 1.0 for Arduino (last updated on 31/10/2012).
PDF Schematics (last updated on 28/08/2012).
ZIP Eagle CAD Schematics and Layout (last updated on 28/08/2012).
ZIP Firmware 1.0 for the DECT Shield (last updated on 31/10/2012).

Additional downloads:

C Bash library 0.1 (last updated on 07/07/2012).

FAQ

Please contact me if you have any question regarding the shield.


Change Log

31/10/2012: