I think that using Modbus to operate a vfd for spindle control is ok, but again the discussion is going back to issues of timing critical functions such as motor and drive control. Simple digital I/O functions would be a much better use for modbus. In my view functions such as home and overtravel switches, E-Stop and power on and off circuits as well as feed hold should be handled by the servo board I/O pins. This brings the hardware watchdog into play on motion critical I/O. The modbus would be useful for things like hand wheel pulses (MPG), external tool and pallet changers and other operator push button functions that are not timing critical. Work lights and coolant on off are not timing critical to the motion control. Machine operators are not consistant in the speed at which they press a button. The software and hardware that reads and writes these functions does not need to be accurate within 20ms. The integrator has to use his head in selecting what I/O point in the entire system is used for what purpose.
Dave On Thu, 2008-10-23 at 10:14 -0400, [EMAIL PROTECTED] wrote: > > Steven demonstrated a working ModBus spindle control running from EMC2 > > to an AutomationDirect VFD at fest this last summer. We didn't try > > anything like threading but it did forward, reverse, and speed. I'm > > only guessing but I don't think the code got into the repository yet as > > it was pretty specific to the device we used. > > Actually, I think I had a concern about the fact that the modbus library > was LGPL3 instead of LGPL2. I'm also not sure if we want to include the > modbus library in the EMC2 source tree (though it's pretty small). > > I'd like to have a generic modbus infrastructure that allows the user to > specify sets of registers, coils and whatnot (there are 4 memory areas in > modbus, if I remember correctly) and the HAL pins they correspond to. > You'd also have to allow for multi-byte values, and packing multiple bits > into one byte. This gets complicated, so I get lazy :) > > The driver I have is for the Automation Direct GS2 VFD, and I think it may > be OK for it to get checked in (once I return home). The question about > including the library still remains though. > > - Steve > > > > ------------------------------------------------------------------------- > This SF.Net email is sponsored by the Moblin Your Move Developer's challenge > Build the coolest Linux based applications with Moblin SDK & win great prizes > Grand prize is a trip for two to an Open Source event anywhere in the world > http://moblin-contest.org/redirect.php?banner_id=100&url=/ > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
