On 02/08/2016 10:12 PM, andy pugh wrote: >> I thought that ModBus was pretty standardized: > So which register do I write to to set output frequency?
Do you have the original documentation of the VFD? I guess not. Do you have any "old" VFD control or test software, If you have, you can reverse engineer the commands quite easily. If not, you have to do (quite a bit) more work. > Which register do I read to monitor motor current? Try and try again, or get a hold of the documentation. ;-) More seriously, fuzzing or educated guessing would probably be my way of finding the right info. > (And, back to the original question, how do I wire the 8 pins on the > VFD to the 2 pins on the adaptor?) Ok, that looks reasonably "easy" and looks like rs422. It has two AA and BB connections, which are most likely a full duplex differential lines. If either AA or BB are opposite polarity, then you can be quite sure that it is differential (use a pull-up when measuring). Then you should be able to see on an oscilloscope if any line sends a peep on power-up. If so you have identified the rx/tx lines, the polarity of the tx line and the default baudrate. Alternatively, the tx/rx lines should be identifiable using injection with a series resistor. The tx lines will stay put, whereas the rx lines will follow the injection. Then, when you have identified the rx lines, you start sending junk (fuzzing) and see what the tx lines do. This way you can identify polarity and baudrate. >From there you can start sending informational modbus commands and see what happens. The 5V line is useful for an in-line isolator. The R and D lines are either feedback or feed-forward lines. You can normally identify input/output by injection with a series resistor and see if the line will bulge in the direction you want it to. -- Greetings Bertho (disclaimers are disclaimed) ------------------------------------------------------------------------------ Site24x7 APM Insight: Get Deep Visibility into Application Performance APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month Monitor end-to-end web transactions and take corrective actions now Troubleshoot faster and improve end-user experience. Signup Now! http://pubads.g.doubleclick.net/gampad/clk?id=272487151&iu=/4140 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
