Not happy using the buttons of your VFD? Then use the built-in data port.
http://fightpc.blogspot.com/2014/10/vfd-control-with-arduino-using-rs485.html
On the Huanyang’s, It’s worth noting that when pd001 is set to Modbus, the multi-inputs are disabled. In case one of them is relied on for E-stop or similar, user needs to know it won’t work anymore.
@Alan_M Stop button still works, but if you use it, it won’t start again until you power cycle the VFD.
hey @Miguel_Sanchez you totally need to add this to smoothie 
lots of people actually waiting for that
@Arthur_Wolf I provided a snippet of code in the blog entry. I used a software serial port (no need to receive just transmit).
@Miguel_Sanchez Yeah thanks for the code it looks simple enough, I’ll see if I can integrate it when I have time
@Miguel_Sanchez Well done. Had similar thoughts myself. When time permits, I’ll try to modify the JSON Serial Port Server used by ChiliPeppr to do the ModbusRTU protocol. It will be interesting to see if different VFD brands use the same ModbusRTU registers (I have an Emerson Commander).
@Michael_Jacobsen apparently they use different registers and values across different manufacturers. Not a big deal but it forces us to customize for each specific VFD.
+Peter van der Walt As a software serial port can be used I reckon it can be integrated on GRBL easily (not sure there is much code free space in Arduino UNO though). Supporting RS485 is a matter of adding one small board (just four wires +5V GND TX & TX output enable).
@Miguel_Sanchez porting smoothie is way too much work at this point I think. Want a Smoothieboard instead ?
@Arthur_Wolf Actually I do have students who need challenging work for their final thesis so hopefully it will be done in a few months.
@Miguel_Sanchez If you need not-so-challenging work for them, get them to get smoothie to control a spindle like you did with the arduino. I’ll provide a free Smoothieboard
@Miguel_Sanchez What do you need ? We have two serial ports on the smoothieboard you could use for this ( one is used for debug, the other is the one we usually plug SPI panels into but can also be configured as an UART ).
@Arthur_Wolf Just two pins would be enough (TX and TX enable) and a SN 75158B driver. However some users may want to have bidirectional communications, so they can query VFD status and verify commands are actually accepted (so RX would be needed too). If a serial port is available then you are all set. A retriggerable timer might be used to enable TX when there is a character transmitted if an extra I/O pin is not available.
@Miguel_Sanchez Yeah then it’s fine, we have uarts and free gpio pins
Easiest here is probably using the main SPI port as an UART ( it can be configured so ), that gives you two free pins on the same connector too ).
Not that I’ve found the exact same registers for stop/start/speed for Emerson, but they’re definitely different 
So to make this versatile, a mapping-function is needed…