Light control with DMX (RS485 at 250kbps, isolated)

[pin_ita]

A lot of lighting devices are controlled using the DMX protocol.
At electric/hardware level the DMX is a cyclic asyncronous trasmission of 513 bytes at 250kbps on a RS485 line.

A standard DMX connection use a 5 pin connector with two RS485 channels, but many devices uses a three pin connector and just one RS485 channel.
Every controlled device use one or more of the 512 channels to know what to do.

I was looking for an handy way to manage two or more DMX lines use a RS485 interface, sending sequences of 513 bytes (one start bit + eight data bits + two stop bits). There is a heading byte and 512 "channels".
The speed is 250.000 bits per second.

There are already some softwares for PC who control some commercial USB to DMX dongles, but I don't know them.

I know some things about electronics and programming and I collected some data and schematics about this case but I cannot draw and produce a printed circuit board and I have not much experience in managing devices as olimex/raspberry/Arduino and such.
So I just put the idea and I am available to work on it, as far I can.

To make some experiments it would be nice to have a programmable device having two or more RS485 isolated ports to be used to receive or to trasmit DMX signals.
About the software, it should be able to
- receive the train of 513 bytes at 250kbps and to map them in memory;
- read a mamory map of 513 bytea and to send them to a RS485 port;
- be connected to a PC (USB?) to be configured.
- or to run a web server, being controlled remotely
- or manage a touch screen to control the channels

An idea could be to have a low level device (a PIC, an Arduino?) to send or receive the data to/from one or more ports, iterfaced with a higher level device to manage the data (manage and recording "scenes" and sequences; copy, split, route, merge channels...).

[cedric]

As far as I can see, the RS485 isolated part is already done, the following board only lacks the DMX connector:
https://www.olimex.com/Products/Modules/Interface/MOD-RS485-ISO/open-source-hardware

Maybe it's a good idea to also create a DMX version of this board.

With this you have a wide range of boards to do the DMX processing.

Kind regards,
Cedric

[jeroends]

I think you 're looking for something like Udmx: http://www.anyma.ch/research/udmx/ or www.illutzmination.de/udmx.html or ...
This is an open source usb dmx interface which is supported by the "ola" project http://www.openlighting.org/. In this way you could create a gateway to a lot of dmx over ethernet protocols.
It's also supported by qlcplus http://qlcplus.sourceforge.net/, this will give you totally what you asked for, but, to get it working on an olinuxino you'll need to do some compilation work (it's already done for the pi).
Personally I use the dongles in combination with ola and use it as an artnet gateway in combination with Martin M-PC http://www.martin.com/product/product.asp?product=m-pc(1 artnet universe for free) and control it with touchosc http://hexler.net/software/touchosc.

ps: qlcplus can also be controlled by touchosc, but in my application qlcplus was a bit to light.