Danfoss VLT5000 VFD control via Modbus/RS485

Did anyone here ever hook up a Danfoss VLT5000 series inverter through Modbus/RS485? I have a VLT5008 coming my way and I would prefer RS485 communication over 0-10V+run/stop+error signals. Setting up the VFD so it accepts control signals over the communication bus is something I can manage, but I'm not sure about he LinuxCNC part. All those different brand inverters seem to talk a slighly different language, right?

At the very least you should be be able to make it work with the generic mb2hal driver.

Documentation is a bit sparse, but enough. Tried to load it 'dry' using halrun, and it does create a set of mb2hal.RegIn.x/mb2hal.RegOut.x pins
That driver seems a ticket to success indeed, thanks!

Now I only wonder if the VLT5000 series supports ModBus serial out of the box or that I need an extra 'ModBus RTU Option Card for that'. It does seem to support a proprietary protocol ('FC protocol') over RS485. Oh well, we shall see once the inverter arrives.

Regarding the RS232->RS485 conversion: Ebay is cheap but takes weeks, local shops are terribly expensive. I do have a couple of SN75176's lying around and a MAX232 should be there also, so it is fairly easy to build the converter. Is using the RTS signal to switch between Rx and Tx mode also valid for LinuxCNC (libmodbus?)

Nice inverter. Manages to run my vacuum pump motor at 10Hz. Lightyears better than 'HuanYang'-class inverters. It only took me two hours of wading through the parameters before I actually got a motor running.

One problem: 'Installed communication module: NONE'.
That means I can talk 'Danfoss FC protocol' and 'Siemens USS/Profidrive protocol' only.

Oh well. I can use 0-10V and a bunch of I/O's to control the VFD. Or maybe adapt an existing driver; that Danfoss FC protocol is quite simple.

My first stab at writing a userspace HAL component seems to work



Well, that was not difficult. At least the HAL-component portion wasn't; serial communication is still not to my liking. Timeout values seem not to do much and the code just hangs on serial port errors.

I attached the source here just in case somebody needs it now. It probably works for other Danfoss VLT drives than the 5000 series also, but I cannot verify that. I expect statusinformation such as the motor power to be bogus, but basic operation such as starting/stopping/setting the frequency/etc. should work as long as the drive talks 'Danfoss FC Protocol'.

The component works fine, but the driver could use some additional robustness and cleanup before 'going public'.

[edit July 10, 2014]
Replaced the component with a better documented and debugged version
[/edit]

OK, I switched to nonblocking I/O so status updates to LinuxCNC continue, added a comm-error pin to indicate that communication is failing, cleaned up some code, and added some documentation.
Does it make sense to submit it somewhere? There are plenty VLT drives on Ebay, so I suppose it is useful for others too?

Like this?
wiki.linuxcnc.org/cgi-bin/wiki.pl?Contri...D_driver_vlt5000_vfd