RS485 Spindle Control

Hey,

I have a Mesa 7i95t board that to my understanding has support for RS485.

I want to connect my Delta MS300 VFD to LinuxCNC over RS485, and I think I have two options:
* I've got a USB RS485 dongle that I can connect to the PC and to the VFD on the other end
* I can connect the Mesa board's RS485 terminals to the VFD

Which one of these options are preferable? Are both these options correct, and are there any pros/cons to either?

Thanks!

I'm no expert, but connecting the VFD to the MESA seems right to me.

Try out both and see!

USB is convenient and inexpensive, but not really optimal.

Using the USB dongle is much simpler and uses supported drivers that are included with Linuxcnc.

Using the Mesa board for controlling an RS485 device is more involved. Someone please correct me if I'm wrong, but I thought that you would be required to a custom firmware that would then need a custom modified Linux driver that supports your specific RS485 device (each device implements Modbus control differently.) There is very little if any documented support for this using Mesa. I've only read a few threads where people were wanting to try this, but I don't think I've seen any posts declaring success, let alone instructions.

Looks like there is more support for Mesa than I was aware of.
linuxcnc.org/docs/2.9/html/drivers/mesa_...us.html#_quick_start

But it still looks more complicated than using USB.

As Todd mentioned, using a USB/RS-485 interface is likely your best option.

Although the HAL component vfdb_vfd.comp was originally designed for the Delta B series VFD, it seems that the Modbus addresses and commands are also compatible with the Delta 300 series. Since you already have everything needed to run a test, please go ahead and share your results. Your findings could be incredibly valuable to others in the future. As you've probably noticed, many users ask questions but rarely follow up with their findings—your feedback will be helpful for others using similar VFD.

linuxcnc.org/docs/stable/html/man/man1/vfdb_vfd.1.html