Sorry for bumping an old thread, but I spent many hours on exactly this issue and finally managed to find a solution. If anyone is still stuck; the cause of my issues turned out to be two-fold:
- I had a good signal on the 485+ pin, none on the 485- pin (checked with oscilloscope).Turns out the DB25 connector had some poor solder joints on the board, I applied some new flux and solder after which the signal was fine. (I think this is why some people are saying you need to screw the connector down tightly… this may push loose pins back against the pcb).
- Still had the “timeout” message when trying to connect to the VFD. Changing the baudrate from 9600 to 19200 on both sides (value 2 for F164 on the HY VFD) solved this. I haven’t checked whether the actual operation worked at 9600b/s, maybe it’s just the timeout label that misbehaved at the default baudrate. I can’t explain this behavior at a signal level, lower should be more stable if anything. The Onefinity does seem to inverse the polarity each “ping” message, probably so you can connect the + and - (A and B) the wrong way around and it will still work, but this means half the messages are garbage and will not receive an answer. Maybe that triggers the timeout at the lowest baudrate; just guessing.
Hope this helps someone!