Hello, I found out about poe only recently. I have tried to build a data-collector application, which queries a number of microcontrollers hidden behind one serial port, connected via rs485 half-duplex connections. Only modest success was achieved ...
It seems to me that I have stumbled across the fact, that the rs485 network is half-duplex. The wheel/filter combination needs to wait for the echoed characters during transmission (allthough that could be changed to no-echo), and after that needs to read up until one of two prompts appear in the response stream. In other words, sending and receiving data is coupled at the wheel/filter level. Every transaction needs to be secured with retry/ timeout operations in order not to get stuck. Finally, the controllers are "quiet" unless they receive the correct address byte. Communication must be initiated with a special byte, on the perl side this goes as normal data (still 8 bit). Questions: 1. Has anyone tried something similar before? 2. Is it a good idea to implement such a system in POE at all? 3. How should I go about writing a "serial-half-duplex" wheel/filter? 4. are there other/better ways to setup a poe application? Probably yes. Any ideas, pointers are highly appreciated. Cheers, Erich
