Anyma uDMX comes with a open firmware, which is rare. The USB communication is handled by the firmware instead of a separate chip. This must be very cheap to build!
While the original device sells for over 200 CHF, there are two clones that use the same firmware but no SMD-devices:
- http://www.illutzmination.de/udmx.html (page german/english)
- http://orikson.piranho.de/pa/uDMX/ (page german)
These two devices are even opto-isolated and use a DC/DC-converter so no risk for the PC/Laptop and no ground loops. Can be built for about 20-30 Euros.
- From USB to DMX (one way DMX)
- All the electronics is inside the XLR - two smd IC's: An AVR microcontroller and a RS485 driver
- The DMX data is buffered and the transmission is timed by the microcontroller
- USB powered
- No galvanic isolation
- Supported by OLA on Linux & Mac
- Supported by QLC (on Windows and probably also Linux and Mac OS, but not well tested)
- An external object for Max/MSP (OSX)
- A console app for Linux/OSX
- MIDI control via a OSX app
- There's an example how to control the console app from php scripts (seems easy)
- Free firmware. The DMX part is GPL, the USB part from Objective Development is "open" but all changes belongs to them.