[Swansea Hackspace] TechHub Buzzer/Access Project

[Justin Mitchell]

On Tue, 2014-11-04 at 18:49 +0000, Paul Harwood wrote:
> What about http://proto-pic.co.uk/categories/wireless/xbee.html
> 
> 
> mentioned here:

XBee sell two main kinds of module afaics

ZigBee 10-100m low power modules.
WiFi modules.

neither help with the audio capture/playback part, which that article
seems to skip over the detail of, they just talk about saving power by
shutting down the wireless data when theres no audio to send

List of problems with possible answers

1. sense buzzer/call, activate door release
1a. easy, any I/O capable board will do; Arduino, RPi, Spark.io, etc

2. capture audio, and play audio to the wired connection
2a. an RPi with a USB sound card type device
2b. A2D and D2A convertors connected to a your favourite microcontroller
2c. A dedicated VOIP convertor device

3. Digitise the audio
3a. The audio will need to be in a suitable format such as RTP used by
VOIP systems, audio compression/decompression is not trivial, neither is
the RTP protocol, but there are libraries to help

4. Transmit audio and control data
4a. Zigbee and bluetooth are too short range
4b. unlicensed radio bands need more specialist transceivers and tend to
also be fairly limited range indoors
4c. wifi at least is ubiquitous and roaming is easy

5. mobile handset
4a. build more or less a mirror of the base station end, ugly
4b. use a smart phone or tablet, pretty but more coding