The Digital Addressable Lighting Interface (DALI) standard is a communication protocol widely used in intelligent lighting applications. Its use is not limited to fluorescent tube lamp dimmable ballasts, for which it was initially designed, but also for future LED applications.
This STEVAL-ILM001V1 hardware module by STMicroelectronics plugs into the STM8S Discovery board allowing you to create a fully working DALI slave application. The STM8S-DISCOVERY + STEVAL-ILM001V1 work as a DALI slave device and can be connected to and controlled by any DALI network.
You can download the data brief for more info. It also contains the schematic, which reveals that this board could be homebrewed for a lot less than the $61.10 list price. (Samples are not available.)
Details on the DALI standard can be found in this 64 page official manual. Also see the STM8 DALI Slave Library app note.
I hope that they make similar KNX (EIB) module.